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Responses of Two Scleractinian Corals to Cobalt pollution and Ocean Acidification. (Tom Biscrere, Riccardo Rodolfo-Metalpa, Anne Lorrain, Laurent Chauvaud, Julien Thebault, and Jacques Clavier.)

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Responses of Two Scleractinian Corals to Cobalt pollution and Ocean Acidification. (Tom Biscrere, Riccardo Rodolfo-Metalpa, Anne Lorrain, Laurent Chauvaud, Julien Thebault, and Jacques Clavier.)

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. We found that, for both species, cobalt input decreased significantly their growth rates by 28% while it stimulated their photosystem II, with higher values of rETR.sub.max (relative Electron Transport Rate)
This article talks about how different kinds of pollution affects two types of coral reefs. It also goes in depth and has a solution to help the coral reefs.

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The effects of ocean acidification alone or in combination with warming on coral metabolism have been extensively investigated, whereas none of these studies consider that most coral reefs near shore are already impacted by other natural anthropogenic inputs such as metal pollution. It is likely that projected ocean acidification levels will aggravate coral reef health. We first investigated how ocean acidification interacts with one near shore locally abundant metal on the physiology of two major reef-building corals: Stylophora pistillata and Acropora muricata. Two pH levels (pH.sub.T 8.02; pCO.sub.2 366 [mu]atm and pH.sub.T 7.75; pCO.sub.2 1140 [mu]atm) and two cobalt concentrations (natural, 0.03 [mu]g L.sup.-1 and polluted, 0.2 [mu]g L.sup.-1) were tested during five weeks in aquaria. We found that, for both species, cobalt input decreased significantly their growth rates by 28% while it stimulated their photosystem II, with higher values of rETR.sub.max (relative Electron Transport Rate). Elevated pCO.sub.2 levels acted differently on the coral rETR.sub.max values and did not affect their growth rates. No consistent interaction was found between pCO.sub.2 levels and cobalt concentrations. We also measured in situ the effect of higher cobalt concentrations (1.06 &#177; 0.16 [mu]g L.sup.-1) on A. muricata using benthic chamber experiments. At this elevated concentration, cobalt decreased simultaneously coral growth and photosynthetic rates, indicating that the toxic threshold for this pollutant has been reached for both host cells and zooxanthellae. Our results from both aquaria and in situ experiments, suggest that these coral species are not particularly sensitive to high pCO.sub.2 conditions but they are to ecologically relevant cobalt concentrations. Our study reveals that some reefs may be yet subjected to deleterious pollution levels, and even if no interaction between pCO.sub.2 levels and cobalt concentration has been found, it is likely that coral metabolism will be weakened if they are subjected to additional threats such as temperature increase, other heavy metals, and eutrophication.

Author(s): Tom Biscéré ¹ , Riccardo Rodolfo-Metalpa ¹ , Anne Lorrain ² , Laurent Chauvaud ³ , Julien Thébault ³ , Jacques Clavier ³ , Fanny Houlbrèque ¹ *

Recent studies have highlighted how coral reefs are extremely delicate systems and how they may easily be altered by human activities (e.g. [1]). Among the main sources of pollution threatening them, metals are conservative in nature, persisting in the environment for long periods [2]. Major inputs of heavy metals to the marine environment include urban storm water run-off, industrial effluents, mining operations, and atmospheric contaminants in both particulate and dissolved forms [3]. Furthermore, motor vehicle emissions, disposal of sewage sludge, dredged spoil, ash and antifouling paints for marine vessels and structures also yield appreciable concentrations of heavy metals to the ocean [2,4,5]. Metal pollution affects many reefs worldwide ( e . g . Costa Rica, Panama, Red Sea, Thailand, Tuvalu, Puerto Rico) [5-9]. Among them, coral reefs of New Caledonia (Pacific Ocean) are particularly concerned by this issue. New Caledonia is among the five major nickel producers in the world and extended portions of its fringing reefs are impacted by extensive nickel mining activities [10], which contribute primarily to metal discharges [11-13]. Among these metals, cobalt is associated with nickel in the laterites of the mining sites and the most recent mines in New Caledonia, and throughout the world, launch the mining of cobalt, as a by-product of the treatment of nickel. Experimental studies on metal potential effects on corals mainly investigated their reproduction and early life stages. They can be summarized in the following: inhibition of coral fertilization and reduced reproductive success [14-16], decreased settlement and survival of coral larvae [17]; changes in the rates of photosynthesis resulted in a decrease in coral calcification and growth rates during the juvenile polyp stage [18,19]; loss of zooxanthellae in coral tissue (also called "coral bleaching") [18,20]; enhanced coral mortality [20,21]. All these experimental studies, using very high metal levels, highlighted the harmful role played by metals when in excess. However, it has never pointed out potential benefic effects due to metals like cobalt (Co), copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) at moderate and representative levels. These metals are indeed essential for the health and growth of corals since they are cofactors of many enzymes [22,23]. Amongst metals, cobalt might play an important role. For example, the vitamin B ₁₂ , also called cobalamine (due to its cobalt nucleus), is involved in the metabolism of all animals and many phytoplanktonic species [24], and stimulates in hospite zooxanthellae growth [25]. Carbonic anhydrases are ubiquitous enzymes known to act as catalysts for the interconversion between CO ₂ and HCO ₃ ⁻ , and it can play an important role when calcification is carbon limited such as under ocean acidification scenarios. However, so far no study has been performed on the direct effect of a cobalt input on coral metabolism.

In addition to waterborne pollutants, the ultimate danger that corals have to face is climate change (e.g. [26]). Atmospheric CO ₂ levels have nearly doubled since pre-industrial times. As CO 2 diffuses in seawater, it behaves like a weak acid leading to a drop in pH on a global scale [27]. About a third of anthropogenic CO ₂ emissions has been absorbed by the oceans, driving the process of ocean acidification during which absorbed CO ₂ transforms into carbonic acid, increasing the concentrations of H+ , bicarbonate (HCO ₃ ⁻ ), and dissolved carbon dioxide (CO ₂ ), while lowering carbonate (CO ₃ ²⁻ ) concentrations and seawater pH [27,28]. The current consensus estimate is that by the end of this century the rate of calcification in scleractinian corals will decrease by 17-37% as a result of reduced seawater [CO 3 ²⁻ ] due to a doubling of preindustrial levels of atmospheric p CO ₂ [29,30] but coral response to acidification is in fact not unequivocal and still puzzling. It has been shown that some tropical species are able to calcify under high p CO ₂ levels [31-34]. Comeau et al . [35], testing eight tropical species demonstrated that response of tropical coral reef communities to ocean acidification was heterogeneous.

To date, no work has studied the combined effect of ocean acidification and metal impacts on corals. Houlbrèque et al. [33] pointed out that zinc uptake rates in Stylophora pistillata were higher under normal pH conditions (pH T 8.1) compared to lower ones (pH T 7.5), suggesting that ocean acidification might also change the incorporation of metals. Depending on whether metals are essential or not, changes in their uptake rates might have radical consequences on coral metabolism.

Here we tested in laboratory conditions the combined effect of ocean acidification and cobalt concentrations on two coral species separately. We also investigated in situ the effects of higher cobalt concentrations on coral metabolism through benthic chamber experiments.

Coral collection and experimental setup

Stylophora pistillata and Acropora muricata were collected in the lagoon of New Caledonia, on the reef of celot Maître (22°19.702Ê¹ S; 166°24.626Ê¹ E). A license has issued by the "Province Sud" to allow this collection. One hundred twenty terminal portions of branches (2-cm long) for each coral species were cut from 10 parent colonies. After collection, S . pistillata microcolonies have been hung on nylon wires and suspended on the aquaria, while A . muricata microcolonies have been glued (Holdfast epoxy) to 2 x 2 cm plastic plates and set up at the bottom of the aquaria. All microcolonies were positioned with the apex in front of the artificial light source. They recovered for one month in the laboratory of the Aquarium des Lagons (Nouméa) under controlled conditions as described below. Microcolonies were randomly assigned to one of the 8 experimental tanks of 20 L volume ( n = 15 per species per tank) supplied with 100 [mu]m-filtered seawater pumped from 5 meter depth in front of the Aquarium. In each tank, seawater was renewed at a rate of 16.5 L h⁻¹ and mixed using a submersible pump (Aquarium system, micro-jet MC 320, Mentor, OH, USA). Temperature (26 ± 0.1°C) and salinity (35.70 ± 0.02) were kept constant using heaters connected to electronic controllers (± 0.2°C accuracy) and routinely verified using an YSI MPS 556 probe (YSI, USA). Corals received a constant irradiance of 120 ± 10[mu] mol photons m⁻² s⁻¹ (photoperiod was 12h:12h light:dark) using four neon Aquablue plus (Blue-white, 15000 Kelvin, Giesemann, Germany). They were fed twice a week during the recovery period and once a week during the experiment with nauplii of Artemia salina (ca. 120 ± 50 nauplii L⁻¹ ).

After the recovery, four tanks were set-up at ambient pH (pH T 8.02 ± 0.03; p CO ₂ 366 [mu]atm) and four others at pH level projected for the end of the century (pH T 7.75 ± 0.06; p CO ₂ 1140[mu] atm) (IPCC 2007). pH was controlled using a pH-stat system (IKS, Karlsbad, accuracy ± 0.05 pH unit) by bubbling independently pure CO 2 in each tank that were continuously aerated with CO ₂ -free air. For each p CO ₂ condition, two tanks received a natural cobalt concentration of the seawater pumped in front of the Aquarium (Natural: 0.035 ± 0.007[mu] g L⁻¹ ), and two others were enriched in cobalt (Polluted: 0.222 ± 0.006[mu] g L⁻¹ ). For that, a peristaltic pump (ISMATEC), together with seawater flow-through, continuously supplied the experimental tanks with solution of stable cobalt (CoNO ₃ , CPAchem, Bulgaria) at a rate 50 ml h⁻¹ . Throughout the experiment, cobalt concentrations have been analyzed once a week by the AEL laboratory ( Analytical Environmental Laboratory ) of Nouméa, according to the protocol described in [36].

Colonies were maintained under these experimental conditions for five weeks, after which their photosynthetic efficiency and growth rates were measured.

Seawater carbonate chemistry

Seawater pH values were continuously monitored by a pH-stat system, which electrodes were calibrated using NBS solutions (Seawater National Bureau of Standards) and adjusted every day to the desired pH T (Total Scale) using a pH meter with a glass electrode (Eutech Instruments EcoScan) calibrated with Tris/HCl referenced solutions ([37]; standards provided by A.G. Dickson, batch 13). Mean pH T were calculated from hydrogen ion concentrations of each measurement and then re-converted back to pH [37]. Total alkalinity was measured twice a week on water samples collected in glass bottles, filtered at 0.45 [mu]m (GF/F Whatman) and stored in the dark at 4°C to avoid biological alteration. The pH was measured at 0.1 ml increments of 0.01 N HCl at 25°C using a Metrohm titration system (848 Titrino Plus). Three replicated 20 mL sub-samples were analyzed. Total alkalinity (A T ) was calculated from the Gran function applied to pH variations from 4.2 to 3.0 as mEq L⁻¹ from the slope of the curve HCl volume versus pH. Titrations of A T standards provided by A.G. Dickson (batch 121) were within 0.85[mu] mol kg⁻¹ of the nominal value. Mean A T of seawater was 2.341 ± 0.047 mmol kg⁻¹ ( n = 40). CO ₂ and saturation states of aragonite ([OHM] ara ) were calculated from pH T , mean A T , temperature, and salinity using the free access CO ₂ Systat package.

Photosynthetic efficiency measurements

Photosynthetic efficiency (F v /F m ) and the relative electron transport rate (rETR) of the Photosystem II (PSII) of zooxanthellae in hospite were measured using a DIVING-PAM fluorometer (Walz, Germany) ( n = 10 for each species and each tank). During measurements light sources were switched off. Ambient light level at the aquarium room was<10[mu] mol photon m⁻² s⁻¹ and did not substantially affect the coral F v /F m . After 15 min of dark adaptation (after [38]), the first measurements were performed. The initial fluorescence (F ₀ ) was measured by applying a weak pulsed red light (3[mu] s, LED 650 nm) on dark-adapted colonies. A saturating pulse (800 ms) of bright actinic light (8,000[mu] mol photons m⁻² s⁻¹ ) was then applied to give the maximum fluorescence value (F m ). Variable fluorescence (F v ) was calculated as F m -F ₀ . At the end of all F v /F m measurements, light was switched on and the corals were allowed to recover under light conditions for 1 h after which rapid light curves (RLC) were generated by illuminating corals for 10·s periods, eight times from 0 to ca. 3000[mu] mol·photon·m⁻² ·s⁻¹ , and the coral maximum relative electron transport rate (rETR max ) was assessed and compared between the different treatments.

During measurements, the 8·mm optical fibre was maintained perpendicular to the coral's surface using a black-jacket at a fixed distance of 5·mm [39]. This system created a quasi-darkness status allowing the rapid re-oxidation of primary electron acceptor [40]. The same setting was also used during F v /F m measurements to guarantee correct distance of the optical fiber to the coral.

It is worth noting that to calculate ETR using RLCs, some assumptions were made. First, because we did not measure the different tissue absorptances between species, we used the relative ETR ( sensu [40]) which does not account for the fraction of incident light absorbed [41]. rETR was therefore uniquely used to compare data from different treatments and not between species. Another source of significant errors when measuring rETR is a likely different symbiont density between samples which can lead to a significant change in reflected light and thus in absorptance. As we measured ETR only one time at the end of the experiment and as the zooxanthellae density did not change between treatments (see Table 1), we are confident that our measurements of rETR reflect coral response to treatment uniquely. It should be noted that pre-configured protocols designed for measuring ETR by PAM fluorometry permit rapid assessment of the light adapted state of corals without allowing sufficient time for steady state conditions to be established, which is required to correctly evaluate the photosynthetic response to light (i.e. ETR vs Irradiance curve [42]). However, our approach was to contrast ETRs between different treatments and therefore contrast relative differences in the responses observed. In no way we measured absolute electron transport rates to contrast relative patterns in light utilization of the two studied species.

Table 1. Summary of two-way ANOVAs testing, in aquaria, the effect of pCO₂ (366 and 1140 ppm) and cobalt concentrations (Natural, 0.03 [mu]g L⁻¹ and Polluted, 0.2 [mu]g L⁻¹ ) on Stylophora pistillata and Acropora muricata main physiological parameters. [see PDF for image]

Microcolonies were weighted ( n = 7 for each species and each tank) using the buoyant weight technique [43]. Samples were weighed using a Mettler AT200 electronic balance (readability 0.1 mg) in seawater of known density as measured by an YSI MPS 556 probe (YSI, USA). For A . muricata , for which samples were attached to plastic plates, they were weighed before and after attachment to tagged plastic plates, and the difference (plate and glue weight) was subtracted from the total weight. The net buoyant weight of the corals (total coral weight minus the weight of each plate) was converted into dry weight using the density of the pure aragonite (2.94 g cm⁻³ ). Their net calcification rates were calculated as the daily change in dry weight between the initial and the final weight and expressed in mg g⁻¹ d⁻¹ .

Zooxanthellae and chlorophyll content

At the end of the incubation microcolonies (n = 3 per each species and tank) were collected and frozen (-20°C) for zooxanthellae and total chlorophyll (chl) measurements. Tissue was removed from coral colonies using an air pick [44] and the slurry was homogenised with a Potter tissue grinder. For each sample, the number of zooxanthellae was counted five times by light microscopy using a Neubauer's cell. Chlorophylls were extracted twice in 100% acetone (24 h at 4°C). The extracts were centrifuged at 10,000 g for 15 min and the absorbances were read at 630, 663, 750 nm. Chlorophyll concentrations were computed according to the spectrometric equations of [45]. All measurements were normalized to the nubbin surface area, which was measured using the aluminum foil technique [46].

In situ experiments were conducted during two consecutive sunny days at the end of August 2012 during the winter Austral season. The study site was located at Tabou Reef (22°28.845Ê¹ S; 166°26.806Ê¹ E) in the southwest New Caledonia lagoon at a depth of 5 m. Three colonies of ca. 15 cm long of A . muricata were sampled by scuba diving near to the study site. Their bare skeleton (due to the collect) was covered by a layer of Holdfast epoxy to avoid the development of algae on this part. Specimens were then transferred to benthic chambers left opened until the beginning of the experiment. Four transparent PVC benthic chambers of 0.19 m diameter and 6.4 L volume were used simultaneously, three chambers containing A . muricata colonies and a control one without coral colony to account for seawater microbial activity. Each chamber was hermetically connected to an YSI 6920 multiparameter probe. Seawater was recirculated between the chamber and the probe at a water flow of 2 L min⁻¹ using an adjustable submersible pump alimented by waterproof batteries [47] (Fig 1). Photosynthetically active radiation (PAR, 400-700 nm) irradiance (I,[mu] mol photons m⁻² s⁻¹ ) was measured adjacent to experimental chambers using quantum sensors (LI-192 SA coupled to a Li-1400 LI-COR). Oxygen, temperature, salinity and depth were recorded every minute inside each chamber with the YSI 6920 multiparameter probe.

Fig 1. Schematic representation of the experimental system. 1- Benthic chamber with a coral colony, 2- Seawater sampling port, 3- Flow meter, 4- Battery in a waterproof housing, 5- Adjustable submersible pump, 6- Multiparameter probe. The arrows indicate the direction of the water flux. [see PDF for image]

During two consecutive days, for each species, six successive incubations of one hour were performed from 11:00 am to 9:00 pm, to encompass the full range of daily irradiance levels, including dark. The first series of incubations has been realized at seawater natural cobalt concentration (less than quantification limit measured by [36]). The second series of incubations have been performed on the same coral colonies but 10 ml of a 17 [mu] mol l⁻¹ cobalt solution have been injected in each chamber at the beginning of each incubation (CoNO ₃ , CPAchem, Bulgaria). Final cobalt concentration into the chambers was equal to 1.06 ± 0.16[mu] g l⁻¹ (i.e. Polluted). Between incubations, enclosures were left open for at least 30 mn to restore ambient conditions.

Photosynthetic, respiration and calcification rates

Photosynthetic and respiration rates, as well as calcification rates associated to A . muricata metabolism were measured during the in situ incubations at different light levels and in the dark. At the beginning and at the end of each of the six incubations, seawater samples were collected with 450 ml syringes in each chamber for pH and total alkalinity (A T ) measurements. pH was measured immediately on board using a pH-meter (Radiometer pH240) calibrated with TRIS/HCl (2-amino-2-hydroxymethyl-1, 3-propanediol) and 2-aminopyridine/HCl buffer solutions in synthetic seawater of salinity 35. Samples were then filtered through 0.7[mu] m Whatman glass-fiber filters (GF/F) and stored in 250 ml bottles in the dark. Total alkalinity ([mu] mol kg⁻¹ ) was further determined on 20 ml subsamples (6 replicates) by Gran automatic potentiometric titration (Radiometer, Titrilab TIM 865) using 0.01 M HCl (see above "Seawater carbonate chemistry" for further details). Total alkalinity values were corrected for ammonium concentrations which were analyzed on board with the fluorometric method [48] (Turner Trilogy fluorometer). These concentrations were negligible and did not modify A T values. The mean standard deviation of replicate measurements was less than 0.003 mmol l⁻¹ .

Calcification rates at each light level and in the dark were estimated using the alkalinity anomaly technique [49] as the difference between the final and the initial A T values of each incubation. Calcification rates (Cnet,[mu] mol CaCO ₃ h⁻¹ ) were estimated for each incubation using the following equation: [see PDF for formula](1) where [DELTA]A T is the variation of total alkalinity during incubation ([mu] mol L⁻¹ ), v is the volume of the benthic chamber (L) and [DELTA]t is the incubation time (h).

Oxygen production and consumption rates were measured by the oxygen sensor of the YSI probe which was calibrated before each experiment against air saturated with moisture. Rates of photosynthesis and respiration were estimated by regressing oxygen data against time. Net photosynthetic rates were calculated according to the following equation: [see PDF for formula](2) where P net is the rate of net photosynthesis ([mu] mol O ₂ h⁻¹ ); v is the volume of the chamber (L); [DELTA][O ₂ ] is the dissolved oxygen variation ([mu] mol O ₂ L⁻¹ h⁻¹ ) during the 1 h incubation.

At the end of all the incubations coral colonies were frozen (-20°C) for further analyses. Photosynthesis, respiration and calcification rates were normalized by unit surface skeleton (cm⁻² ), which was measured using measured using the aluminum foil technique [46].

For each colony, a Michaelis-Menten model [50,51] was iteratively fitted using non-linear regression (Gauss-Newton algorithm) to P net versus in situ PAR irradiance (I,[mu] mol photons m⁻² s⁻¹ ), according to the following equation: [see PDF for formula](3) where P max is the gross maximal production rate ([mu] mol O ₂ cm⁻² h⁻¹ ), K m is the half saturation constant ([mu] mol photons m⁻² s⁻¹ ), and R is the respiration in the dark ([mu] mol O ₂ cm⁻² h⁻¹ ).

From the equation above, P max and K m have been calculated (Eqs 4 and 5): [see PDF for formula](4) [see PDF for formula](5)

The same procedure was also used to fit calcification rates (C net ) versus Irradiance values. Eqs 6 and 7 were therefore used to calculate maximum fitted calcification values (C max ) as follow: [see PDF for formula](6) [see PDF for formula](7) where C max is the gross maximal calcification rate ([mu] mol CaCO ₃ cm⁻² h⁻¹ ), K m is the half saturation constant ([mu] mol photons m⁻² s⁻¹ ), and C dark is the calcification rate measured in the dark (i.e. dissolution,[mu] mol CaCO ₃ cm⁻² h⁻¹ ).

For the aquaria experiment, three-way ANOVA factorial analyses were used to test the effects of pH (normal and low), cobalt (normal and polluted) and tanks (two replicates), independently for each of the two species. All data were tested for the assumptions of normality and homoscedasticity using Shapiro Wilk's test and Cochran's c-test respectively. After verification of the absence of significant differences between tanks (ANOVA, p > 0.05), data were pooled before proceeding to test for main effect using two-way ANOVAs. Two-way ANOVAs were used to test the effects of pH T and cobalt concentrations on zooxanthellae density, chl concentration, net calcification rate, photosynthetic efficiency (F v /F m ) and maximum electron transport rate (rETR max ). All the tests were performed using PRISM software (Statsoft). When the ANOVA determined a significant difference, a Tukey's honest significant difference test (HSD) was used to attribute differences between specific factors. All data are expressed as the mean ± SD. For each in situ experiment P max , K m and R, as well as C max and C dark were compared between cobalt concentrations (i.e. natural vs. polluted) using F-test according to [52].

Zooxanthellae density did not differ between experimental treatments (2-way ANOVA, p > 0.05; Table 1) for both S . pistillata (pooled data, 1.06 x 10 ⁶ ± 2.26 x 10 ⁵ cells cm⁻² ) and A . muricata (pooled data, 1.21 x 10 ⁶ ± 1.84 x 10 ⁵ cells cm⁻² ). Chl a concentrations slightly but significantly varied between p CO ₂ (6.04 ± 1.9 and 7.10 ± 1.1[mu] g chl cm⁻² at pH T 8.1 and 7.8 respectively) and its interaction with cobalt (6.04 ± 1.9 and 7.10 ± 1.1[mu] g chl cm⁻² at Natural and Polluted concentrations respectively) for S . pistillata (interaction p CO ₂ x Metal F 1,20 = 12.38, p = 0.002; Table 1), but not for A . muricata (pooled data: 6.389 ± 1.242[mu] g chl cm⁻² ; Table 1).

Concerning their photosynthetic properties, both coral species did not show uniform responses to experimental treatments (Figs 2 and 3). For S . pistillata , F v /F m and rETR max significantly differed between treatments (2-way ANOVA, p<0.05, p<0.01 respectively; Table 1). F v /F m was not affected by p CO ₂ treatment (2-way ANOVA, p > 0.05; Table 1) but was enhanced by cobalt with higher values at the polluted metal concentration (Tukey test, p<0.05), while rETR max values showed an interaction between p CO ₂ and cobalt (2-way ANOVA, F 1,36 = 5.30, p = 0.027; Table 1). On the opposite, A . muricata F v /F m were not affected by both cobalt concentration and p CO ₂ treatments (2-way ANOVA, p > 0.05; Table 1), while rETR max values for this species significantly varied between treatments (2-way ANOVA, p > 0.05; Table 1). They increased at polluted cobalt concentrations but decreased at elevated p CO ₂ level (Tukey test, p<0.01 and p<0.05 respectively) (Fig 3).

Fig 2. Effective photosynthetic efficiency (Fv /Fm ) measured on dark adapted Stylophora pistillata and Acropora muricata colonies exposed during five weeks to two pHT conditions (pHT 7.8 or 8.1) and two cobalt concentrations (Natural and Polluted). Stars indicate statistically significant differences (Tukey's test, p <0.05). Each point represents the mean ± SD ( n = 10). [see PDF for image]

Fig 3. Relative electron transport rate (rETR) versus irradiance (PAR) for colonies of Stylophora pistillata (a) and Acropora muricata (b) (mean ± SD, n = 10) exposed during five weeks to two pHT conditions (pHT 7.8 or 8.1) and two cobalt concentrations (Natural and Polluted).

Coral growth rates for both species were not significantly affected by p CO ₂ treatments but significantly by cobalt (2-way ANOVA, p > 0.05; Table 1 and Fig 4). Polluted cobalt concentrations significantly decreased their growth rates (Tukey test, p<0.01) with values of 4.68 ± 1.44 mg g⁻¹ d⁻¹ and 6.88 ± 1.62 mg g⁻¹ d⁻¹ for S . pistillata and 3.57 ± 1.31 and 4.66 ± 1.48 mg g⁻¹ d⁻¹ for A . muricata at polluted and natural cobalt concentration respectively.

Fig 4. Growth rate (mg g⁻¹ d⁻¹ ) measured for Stylophora pistillata (a) and Acropora muricata (b) colonies after five weeks of incubation under two pHT conditions (pHT 7.8 or 8.1) and two cobalt concentrations (Natural and Polluted). Data are mean ± SD ( n = 14). [see PDF for image]

Rates of maximal gross photosynthesis (P max ) per unit surface area were significantly lower on A . muricata incubated with cobalt than exposed to natural concentrations (0.77 vs. 1.16 [mu]mol O ₂ cm⁻² h⁻¹ ; F-test = 15.05, p = 0.000; Fig 5a). Cobalt also significantly affected (F-test = 12.51, p = 0.001) the half saturation constant (K m ), with much lower values measured for colonies incubated with a cobalt supply (115.29 vs. 408.41[mu] mol photons m⁻² s⁻¹ ). No significant differences in the respiration rates were found (R = -0.28 vs. -0.24 [mu]mol O ₂ cm⁻² s⁻¹ , respectively) (F-test = 15.05, p > 0.05).

Fig 5. Acropora muricata photosynthetic (a) and calcification rates (b) measured in situ during benthic chamber incubations at Natural (<0.03 [mu]g L⁻¹ ) and Polluted (1.06 [mu]g L⁻¹ ) cobalt concentrations.

Cobalt significantly affected the growth of A . muricata (Fig 5b), with both maximal light calcification (C max : F-test = 6.33, p = 0.02) and dark calcification rates (C dark : F-test = 4.80, p = 0.04) lower for corals submitted to cobalt (0.120 and 0.030 [mu]mol CaCO ₃ cm⁻² h⁻¹ for C max and C dark respectively) than in natural seawater (0.453 and 0.070 [mu]mol CaCO ₃ cm⁻² h⁻¹ for C max and C dark respectively).

Ocean acidification is one of the major threats that tropical coral reefs are facing during this century. Key life functions in corals, such as growth and photosynthesis, have been shown to be affected by high p CO ₂ levels (i.e. [27,30]). In addition, near shore coral reefs are often already weakened by coastal human impacts, such as metal pollution, but the combination of ocean acidification and these other anthropogenic pollution forms has not been investigated yet. Thus, this study(i) examined, in laboratory conditions, the responses of two corals to the combination of metal pollution (here the cobalt) and ocean acidification and(ii) determined in situ whether a cobalt input alters the main coral physiological parameters. Cobalt levels added into the experimental tanks and the benthic chambers are realistic since they are in the range of maximal concentrations measured along the coasts of New Caledonia [36]. Our experiments highlighted that even a moderate cobalt concentration (0.2[mu] g L⁻¹ ), and without interaction with acidification, adversely affects the growth of both coral species and that an increase in cobalt concentration to 1.06[mu] g L⁻¹ leads not only to coral growth decrease, but also to an inhibition of their photosynthesis process.

Effect of cobalt enrichment on coral physiology

One of the major results of this study is that, at cobalt concentrations regularly measured along the New Caledonian coasts for example (0.2 [mu] g L⁻¹ ) [36] a decrease of 28% in growth rates is already observed for both species. Furthermore, in situ incubations of A . muricata colonies at a higher concentration (ca. 1[mu] g L⁻¹ ) confirmed these results, revealing coral calcification rates of 70% lower than at normal cobalt concentrations. Although no study so far have measured the effects of cobalt on coral growth, our result is in agreement with [53] which demonstrated, for a coccolithophoridae species, Cricosphaera carterae that a cobalt concentration of 200[mu] moles L⁻¹ leaded to a decrease in calcium ion incorporation rates. Therefore, our results suggest that near shore reef corals may greatly suffer from metal pollution and, in turn, may be less prone to resist to other anthropogenic stresses.

As calcification and photosynthesis mechanisms are coupled in symbiotic corals [29], one should expect that the decrease in calcification rates observed in the present study was combined to an inhibition of the photosynthetic efficiency and/or the zooxanthellae. However, during the laboratory experiment, the F v /F m measured in S . pistillata and A . muricata (ranging from 0.6 to 0.7), exposed to an ecologically relevant enrichment in cobalt (0.2[mu] g L⁻¹ ), revealed that their photosynthetic processes were stimulated by such moderate cobalt input and were operating at their maximum capacity [54]. Rather, this moderate cobalt concentration stimulates the rETR max values in S . pistillata and A . muricata . On the other hand, their zooxanthellae concentrations did not change, suggesting that, unlike iron [19], cobalt addition did not stimulate symbiont densities but would rather stimulate the photosynthetic efficiency of these algal cells. This is consistent with previous studies performed on the same coral species, showing a stimulation of rETR max values in response to a moderate zinc or iron input [19,55]. Two hypotheses may explain this stimulation:(i) as cobalt is a cofactor of the carbonic anhydrase, an additional input would stimulate this enzyme and would bring additional inorganic carbon to the photosynthetic process [56,57];(ii) as coral gastric activity harbors a bacterial community able to produce the B12 vitamin, named cobalamin (due to its cobalt core), an enhancement of this vitamin production could stimulate the photosynthetic process [58].

When cobalt was equal to ca. 1 [mu] g L⁻¹ , in the in situ experiments, photosynthetic rates per unit surface area decreased, suggesting that the toxic threshold for zooxanthellae in A . muricata was reached. This result is consistent with previous studies, in which a clear inhibition of the photosynthetic efficiency of the two branching corals Acropora cervicornis and Pocillopora damicornis was observed, when they are exposed to elevated copper levels between 4 and 20[mu] g L⁻¹ [59]. Furthermore, as metals are mostly accumulated in coral tissues and more particularly in symbiotic algae [55], their expulsion is thought to be a mechanism of metal detoxification. Although our in situ incubations were too short to detect a change in the zooxanthellae density and no measurements have been performed, it is likely that the cobalt level tested reached the zooxanthellae toxic threshold affecting whole coral metabolic functions. Zooxanthellae expulsion was observed for Acropora formosa and Porites lutea exposed to extreme copper and iron concentrations, from 10 to 100 times higher than the concentrations measured in coral reef surrounding waters [18,60]. In conclusion, our results show that while extreme cobalt concentrations may be lethal for corals, reducing calcification and photosynthetic metabolism, a moderate concentration effect may be more species-specific. Two hypotheses may likely explain this antagonism:(i) algae and host may be in competition for inorganic carbon for photosynthesis and calcification [19,61,62] but the coral ability to compete for this substrate may be highly species-specific with some species able to preferentially allocate inorganic carbon to the photosynthetic process;(ii) moderate cobalt concentration might be toxic for the host cells but not yet for the zooxanthellae. Despite these observations, identifying the mechanisms underlying the enhancement of the photosynthetic process or the calcification decrease is beyond the scope of our study and we suggest that further research should be conducted.

Effect of pCO₂ increase on coral physiology

Higher p CO ₂ levels did not affect the photosynthetic efficiency of both coral species but caused an opposite effect on their rETR max values, stimulating S . pistillata and inhibiting A . muricata . Previous studies focused on the effects of ocean acidification on photosynthetic processes gave ambiguous results. While the lack of impact for S . pistillata have been already noticed during short-term studies [33,63-66] and are consistent with the assertion that corals do not rely on dissolved CO ₂ for their photosynthesis [29]; other studies rather highlighted a detrimental effect of p CO ₂ on the coral photosynthetic efficiency [67,68]. Response heterogeneity among corals would be linked to the symbiont types [69].

No change in the growth rates of S . pistillata and A . muricata was detected between the different p CO ₂ conditions. These results confirm a recent study performed on S . pistillata , where all coral fragments submitted for one month to high p CO ₂ conditions (2,039[mu] atm) survived and showed equivalent calcification rates to corals submitted to normal conditions [33]. Although these results should be taken with caution, since corals were incubated during short periods to low pH, it is consistent with some previous studies showing that some corals are able to calcify at low-pH seawater (e.g. [32,44,70-73]). Coral species like S . pistillata and A . muricata would be part of a "low-sensitivity" group to p CO ₂ [74] and to the "potential winners" that would be able to control pH at their calcification site [73] and would outcompete species unable to do it [34]. Furthermore, ocean warming should also to be taken into consideration as [64] showed that S . pistillata was insensitive to doubled p CO ₂ at 25°C but on the other hand experienced a 50% reduction in calcification rate at a higher temperature (+ 3°C). So, based on changes in temperature, some coral species like S . pistillata could shift between insensitivity and high sensitivity to p CO ₂ increase.

Even if no interaction between p CO ₂ levels and cobalt concentration has been revealed in our study for these two coral species, it is likely that coral colonies, for which growth rates already decrease by 28% when submitted to a moderate cobalt input, will be weakened if they are subjected to additional threats (i.e. temperature increase, other metal pollution, eutrophication). Indeed, when their temperature threshold has been exceeded or when corals are submitted to a poor seawater quality, it has been widely demonstrated that they stop their growth and expel their zooxanthellae (e.g. [62,75,76]) and so a cobalt pollution would exacerbate these phenomena.

It is also likely that species originally classified into the "highly sensitive group" such as Porites lutea or Acropora cervicornis for example [77] will be probably more drastically affected by metal inputs. In addition, our results only correspond to a five weeks incubation experiment and as it has been demonstrated that metals accumulate in coral tissues [55], a longer-term experiment should induce a stronger calcification inhibition and an overrun of the toxicity threshold for the zooxanthellae. Previous studies performed on other marine organisms like copepods and polychaetes demonstrated that metal pollution increases their sensibility to ocean acidification [78,79] and the present study clearly indicates that it is also the case for corals.

We wish to thank R. Farman, L. Foure and the technical staff of the Aquarium des Lagons (Nouméa) for their welcome and assistance in tank maintenance. We would like to thank E. Amice and the crew of the R/V ALIS for their help during the benthic chamber experiment, as well as M. Milazzo for statistical advice. This is ENTROPIE scientific contribution n. 27.

Conceived and designed the experiments: TB RRM AL FH. Performed the experiments: TB RRM AL LC JT JC FH. Analyzed the data: TB RRM AL JC FH. Contributed reagents/materials/analysis tools: TB RRM AL LC JT JC FH. Wrote the paper: TB RRM AL JT JC FH.

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1 Laboratoire d'Excellence " CORAIL", Institut de Recherche pour le Développement, ENTROPIE (UMR9220), BP A5, 98848, Nouméa cedex, New Caledonia, 2 IRD/ R 195 LEMAR, IRD Nouméa, BP A5, 98848, Nouméa cedex, New Caledonia, 3 Université de Brest, Institut Universitaire Européen de la Mer, Laboratoire des sciences de l'environnement marin (UMR6539 CNRS/IRD/UBO), rue Dumont d'Urville, 29280, Plouzané, France

Academic Editor: Candida Savage, University of Otago, NEW ZEALAND

Copyright: © 2015 Biscéré et al

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Data Availability: All relevant data are within the paper.

Funding: Part of this study was supported by the Laboratoire d'Excellence (LabEX Corail), the Institut de Recherche pour le Développement (IRD) and the Institut National des Sciences de l'Univers (INSU) through the PNEC/CITRIX IBANOE program of Initiative Structurante Ecosphère Continentale et Côtière (EC2CO).

Competing interests: The authors have declared that no competing interests exist.

Corresponding Author: * E-mail: fanny.houlbreque@ird.fr

DOI: 10.1371/journal.pone.0122898

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# data[].attributes.attachment_link.title
Responses of Two Scleractinian Corals to Cobalt Pollution and Ocean Acidification

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The effects of ocean acidification alone or in combination with warming on coral metabolism have been extensively investigated, whereas none of these studies consider that most coral reefs near shore are already impacted by other natural anthropogenic inputs such as metal pollution. It is likely that projected ocean acidification levels will aggravate coral reef health.

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This link leads to facts and statistics about how much ocean pollution has increased each year

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Marine pollution is the detrimental alteration of a portion of an ocean or ocean coastline. Pollution is often a threat to any organism living in or depending upon the ocean. Human impact on coastal and open ocean habitats comes in many forms: nutrient loading from agricultural runoff and sewage discharges, toxic chemical inputs from industry and agriculture, petroleum spills, and inert solid wastes.

Nutrient loading is perhaps the most well-studied form of pollution, and its biological consequences have been observed and documented. Algal blooms, including red tides, have been attributed to elevated nutrient levels in coastal systems. These blooms, through their respiration and decomposition, can deplete the levels of dissolved oxygen in the waters to almost zero, killing zooplankton, fish, and shellfish. These nutrients often come from runoff of agricultural fertilizers, the use of which has increased seven-fold since 1950. More than 50 percent of the rivers in the United States are currently considered to be in poor health due to fertilizer contamination. Studies have indicated that approximately half the fertilizers and pesticides used in the United States end up in waterways and coastal marine environments.

From 2015-2016, a bloom of Karenia brevis, a single-celled phytoplankton algae that releases a deadly neurotoxin, produced a record-setting red tide along the north central Gulf Coast. Wave mixing also created an aerosolized form of the neurotoxin that required public health officials to issue warnings to people with respiratory problems who lived or worked near the beach. The bloom was fed by elevated nutrient levels and, through both respiration and decomposition, depleted levels of dissolved oxygen in the water. The record setting red tide, at the time the worst ever observed in some areas, killed marine life and birds broadly across the food chain, from zooplankton to fish and shellfish. The blooms also killed sea turtles, sharks, dolphins, and birds from the Mississippi Sound to the Florida Panhandle. It was followed by another, longer outbreak that lasted from October 2017 into 2019.

Another source of nutrients is the discharge of sewage. Throughout the world, raw sewage is released into rivers and coastal habitats by many countries, leading to algal blooms and increased biochemical oxygen demand (BOD). BOD, the rate at which oxygen disappears from a sample of water, increases dramatically with loading of organic material such as sewage, and results in the lowering of dissolved oxygen levels. The wastes of domesticated animals may also have a major impact in some systems. A single cow produces approximately thirty-one pounds (fourteen kilograms) of waste per day, the equivalent of ten people. When discharged into rivers or coastal waters, wastes produced by large herds or feedlots may have substantial effects.

Toxic substances are introduced into the marine environment from various sources, some of which may be hundreds of kilometers away. Heavy metals, pesticides, and acid rain threaten not only coastal and estuarine systems, but also life in the open ocean. Heavy metals occur in many forms, some of which are soluble in seawater. These soluble compounds may not be the forms in which they were originally released into the environment, often making their sources difficult to determine. Many heavy metals are released in industrial effluents, especially from chemical plants, smelters, and mining runoff. These compounds may affect humans directly through contact, or indirectly, from the consumption of fish and shellfish, where metals often accumulate in tissues.

Acid precipitation is rain, snow, or fog that has a lower pH than normal and is caused by inputs of nitric (HNO ₃) and sulfuric acid (H ₂SO ₄) into the atmosphere from manufacturing and the burning of fossil fuels, originating from industrial processes and automobiles. These causes may be far from the area of impact, since prevailing winds can carry pollutants considerable distances. The ocean has a high buffer capacity, that is, the ability to neutralize many of the acid inputs. Therefore, most of the severe effects of acid rain are observed in freshwater lakes and rivers. Some estuaries, however, may also be seriously affected, as has been observed in the upper Chesapeake Bay. The pH of a river feeding the Bay dropped from 6.3 to 5.8 between 1972 and 1978. Juvenile and spawning striped bass may not be able to tolerate such high acidity. Precipitation of nitrogen-based acid also increases nutrient loading in aquatic systems.

One of the most publicized sources of marine pollution is that caused by petroleum products. While large oil spills can devastate a local area, equally important is the discharge of crude oil while cleaning bilges and emptying tanks at sea. In the period from 2010 to 2018, there were 59 spills of 2,000 gallons or more. Since tanker ports and refineries are, by necessity, located on the coast, these sensitive areas receive considerable damage from the spills. The damage to marine life is staggering. Large numbers of seabirds are killed annually, their oil-matted plumage making flight impossible and exposing them to hypothermia. Oil-soaked fur of marine mammals loses its water repellency, also leading to death by hypothermia. Ingestion of oil by fishes, birds, and mammals may also result in death.

On April 20, 2010, an explosion on the Deepwater Horizon drilling rig in the Gulf of Mexico destroyed the structure and triggered an oil leak on the ocean floor. For 87 days, oil spewed into the Gulf, with only a fraction of the more than 200 million gallons of polluting crude oil collected by a fleet of recovery vessels. Millions of gallons of chemical dispersants were also used. While the extensive use of dispersant chemicals was at first trumpeted as an effective means of removing much of the threat to wildlife, fisheries, and coastal habitats from the massive amounts of surface and underwater oil, later studies have demonstrated that substantial amounts of oil remains mated in seafloor residue or encased in tar balls. Long term ecological impact studies continue.

Hundreds of tons of inert solid wastes are dumped into the oceans from ships annually. Of these, plastics and polystyrene (styrofoam) are deadly to marine life. Often floating for hundreds of miles and lasting for many years, plastics are frequently mistaken for food by fishes, turtles, and mammals, and proceed to either interfere with subsequent feeding or strangle the consumer. It has been estimated that plastics and discarded fishing gear, such as monofilament line and discarded nets, kill one million seabirds and 150,000 marine mammals each year.

Beginning with the Refuse Act of 1899 and the Water Pollution Act of 1948, there have been efforts to remedy the polluted oceans. Not until 1972, however, was legislation drafted that was powerful enough, and sufficient monies appropriated, to effect any change. With the Federal Water Pollution Act, or Clean Water Act, improvement of water quality in the United States began. By 1985, five of the goals of the 1972 Act were reached, and since then, the Clean Water Act has been amended to reflect increasing national concerns.

Pollution of the world's oceans had become so pervasive that an international convention met in 1972 to establish laws governing the discharge of all wastes into the ocean. The Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (or London Convention) was entered into force in 1975; it prohibited the dumping of certain hazardous wastes, required a special permit for a number of identified materials, and required a general permit for other wastes. Amendments to the London Convention included the banning of radioactive waste dumping, the phasing out of dumping industrial wastes by 1995, and the banning of incinerating industrial wastes at sea. The 1996 Protocol was enacted to replace the London Convention, taking a "precautionary approach" to dumping and the potential effects of dumping on the environment and aquatic ecosystems. According to the protocol, proposals for dumping had to provide proof that the deposition of waste would not harm the environment. The 2006 amendment to the 1996 Protocol was adopted to allow carbon dioxide (CO ₂) storage, a process termed carbon sequestration, under the seabed as of February 2007 in order to reduce the amount of carbon dioxide in the atmosphere. This amendment regulates carbon capture and storage (CCS) in sub-seabed geological formations for permanent sequestration to mitigate climate change. The International Convention for the Prevention of Pollution from Ships (1978), commonly known as MARPOL, and subsequent annexes to the convention, covers all garbage discharged by normal operation of ships at sea beyond three miles from shore. While it is too soon to tell, adherence to the MARPOL agreement should significantly reduce the amount of solid wastes polluting the world's oceans.

The 2011 Fukushima nuclear disaster released radioactive wastewater used in reactor cooling operations into the sea off the coast of Japan. Officials established an exclusion zone (both on land and at sea) around the damaged plant while monitoring radiation levels. A May 2012 World Health Organization (WHO) study found elevated radiation levels of 10-50 millisieverts (mSv) near the Fukushima plant in towns of Namie and Itate. Most other areas in Fukushima prefecture had radiation levels of 1-10 mSv (individuals typically receive around 2 mSv of environmental radiation per year). The report indicated near-normal to normal levels of radiation in remote areas of Japan and neighboring countries, but evidence of marine radiation pollution was located as far away as California where another group of researchers found Pacific tuna populations with safe but elevated levels of cesium traceable to the Fukushima nuclear accident. Researchers in August 2013 found that the damaged site continued to leak contaminated water used in cooling operations into local ground and ocean waters.

Source Citation

Gale Document Number: GALE|CV2644150832

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Marine pollution is the detrimental alteration of a portion of an ocean or ocean coastline. Pollution is often a threat to any organism living in or depending upon the ocean. Human impact on coastal and open ocean habitats comes in many forms: nutrient loading from agricultural runoff and sewage discharges, toxic chemical inputs from industry and agriculture, petroleum spills, and inert solid wastes.

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Viewpoint – Ocean Plastic Pollution: a convenient but distracting truth? (Richard Stafford and Peter J.S. Jones)

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Viewpoint – Ocean Plastic Pollution: a convenient but distracting truth? (Richard Stafford and Peter J.S. Jones)

# data[].attributes.body
- "...potential to provide ‘quick fix’ technological solutions to plastic pollution, such as large scale marine clean-up operations and new ‘biodegradable’ plastic substitutes. As such, ocean plastic can provide a convenient truth that distracts us from the need for more radical changes to our behavioural, political and economic systems, addressing which will help address larger marine environmental issues, as well as the cause of plastic pollution, i.e. overconsumption."

- "Public opinion has also altered industry behaviour and even
government policies as a result of the high levels of public concern over plastic waste."

-"Anthropogenic greenhouse gas emissions, largely from the burning of fossil fuels, are causing oceans to warm and acidify. Coral reefs bleach more frequently and have less recovery time with warming temperatures, and predictions have indicated that coral reefs will be under severe threat unless
temperature rises are urgently limited. Climate change also affects many other marine systems... Climate change impacts are also associated with changing species and disease distributions, particularly from hotter lower latitude regions towards the poles, and such changes can also cause major ecological community change, and potentially also negatively affect biodiversity."

- "Overfishing, along with
associated habitat damage from bottom trawling, is drastically changing many ecological communities in our oceans, making them less resilient and potentially less able to supply food and other ecosystem services to the most vulnerable communities who rely on fish as a source of protein."

- "For example, permanently changing diet away from meat and
many kinds of fish is needed [36] as is reducing consumerist consumption patterns, car reliance and aeroplane flights, or more controversially, reducing our number of children. As such, a focus on individual level action, at least at the level of the ‘how to make a difference’ checklists common on social media, is unlikely to successfully address the complex environmental issues we face today, and may even be a distraction from the need to make structural changes to our societal, political and economic systems."

- "For climate change and biodiversity loss, technical solutions
allow further reuse and recycling of products, reducing the energy requirements of production and
limiting the extraction of natural resources which may lead to habitat degradation and biodiversity loss. As such, technological solutions can play a role, but achieve the most when combined with a new political and economic outlook to the environment."

- "For example, while flying is one of the major individual level changes which can be made to reduce carbon emissions, globally it equates to < 2% of carbon emissions, due to the low number of people flying at a global level... reduction of meat consumption would have a far greater reduction in carbon emissions. While reduction in flying is clearly important, at a political level, it would be more effective to tax meat consumption or production the reduce carbon (although the optimal solution may vary by country)."

- "Individuals need to target political systems to create real environmental change. At its most basic form, this should include voting, but as history demonstrates, collective action relies on education (often
informal education and discussion) and challenging the status quo of debate. Developing effective
environmental governance strategies at local, national and global levels is also likely to provide
integrated solutions to environmental problems, but also strengthen the case for political
reform."

# data[].attributes.headline
 Can Social Media Clear the Air? A Case Study of the Air Pollution (Samuel Kay, Bo Zhao, and Daniel Sui) 

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 Can Social Media Clear the Air? A Case Study of the Air Pollution (Samuel Kay, Bo Zhao, and Daniel Sui) 

# data[].attributes.body
- We find that... microblogs are capable of empowering citizens to advance an environmental cause..."

- At the urging of the International Olympic Committee (IOC), the Chinese government shut down hundreds of factories, power plants, and construction sites within a 150-km radius of Beijing; removed millions of vehicles from the road; planted trees to prevent sandstorms; and seeded clouds to
change the weather. These costly efforts resulted in a significant reduction in air pollution in Beijing (Rich et al. 2012). The emissions reduction coincided with a
drop in biomarkers of cardiovascular disease among
young adults, which increased again when the games and air pollution reduction measures ended."

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IRRSource2 Can Social Media Clear the Air A Case Study of the.

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Marine & Ocean Pollution Statistics and Facts 2020-2021- Condor Ferries

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Marine & Ocean Pollution Statistics and Facts 2020-2021- Condor Ferries

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Link

-"Marine life, as we know it, is suffering irreparable damage from the chemical pollution of the waters and the millions of tons of mismanaged waste dumped in the oceans each year. The result is a planetary crisis with over 100 million marine animal’s lives get lost every year, and the decay of the ocean's ecosystem."

-"1 in 3 marine mammal species get found entangled in litter, 12-14,000 tons of plastic are ingested by North Pacific fish yearly. "

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Ocean Pollution: Public Awareness and Action- Sea Life Foundation

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Ocean Pollution: Public Awareness and Action- Sea Life Foundation

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LINK
- "The Sea of Change Foundation seeks, guides, and funds projects that directly address this critical issue by educating and empowering consumers, communities, and industries to make more sustainable choices. We are working towards meaningful change towards decreasing plastic pollution"

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Why The Sudden Interest In Ocean Pollution - GreenBiz Rob Kaplan

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Why The Sudden Interest In Ocean Pollution - GreenBiz Rob Kaplan

# data[].attributes.body
LINK
-"In May, the Australian government set a target for 100-percent reusable, compostable or recyclable packaging by 2025; two months later, the Australian senate recommended a ban on all single-use plastics, including takeout containers, plastic-lined coffee cups, chip packages, and bags — by 2023."
-"In July, PepsiCo committed $10 million to the "All In On Recycling" initiative to increase recycling rates in the United States and capture 7 billion containers over the next five years."
-"Charles Moore brought back the first reports of the "plastic garbage patch" in 1997. Since then, we’ve learned that 150 million tons of plastic are in the ocean, much of it from countries taxed with processing exponential levels of plastic with little or no waste management systems. The number has increased by 8 million tons each year as developed countries focus on eliminating single-use plastics such as straws — which represent less than 1 percent of ocean plastic — rather than systemic change."

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Ocean Optimism: Raising Awareness- Ocean Climate Lab

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Ocean Optimism: Raising Awareness- Ocean Climate Lab

# data[].attributes.body
LINK
-"Corporations, companies, and organizations can be examples for doing their part in helping the environment and providing educational resources for the public."

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Raising Awareness of Plastic Hazards- Earth D.E.C.K.S.

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Raising Awareness of Plastic Hazards- Earth D.E.C.K.S.

# data[].attributes.body
LINK
-"The diversity of the plastic problem requires
• a diversity of talent; different types of organizations
• champions with diverse expertise and different approaches
• both big ideas and continuous improvement
• continually trying new experiments and engaging new champions"

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5 Ways Technologies Are Helping Beat Plastic Pollution- eTrade For All

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5 Ways Technologies Are Helping Beat Plastic Pollution- eTrade For All

# data[].attributes.body
LINK
-"They are using satellite imaging and machine learning to help clean up and capture the 5 trillion pieces of plastic trash they have observed in the world’s “ocean garbage patches.” They estimate that within 5 years they could collect 50% of the ocean’s garbage."
-"This year the UNEP campaign, #BeatPlasticPollution, aims to get people to pledge to give up single use plastics. Using social media awareness, they are raising funds and challenging teams to hold events across the globe."

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9 Companies Using Social Media Awareness About the Plastics Industry

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9 Companies Using Social Media Awareness About the Plastics Industry

# data[].attributes.body
LINK
-"We have produced more plastic over the last ten years than during the whole of the last century

14% of all litter comes from beverage containers, and when you add in caps and labels the number increases

Packaging is the largest “end use market” segment, accounting for about 40% of total plastic usage"

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Marine Pollution Explained- National Geographic 

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Marine Pollution Explained- National Geographic 

# data[].attributes.body
LINK
-"Before 1972, humans around the word spewed trash, sewage sludge, and chemical, industrial, and radioactive wastes into the ocean with impunity. Millions of tons of heavy metals and chemical contaminants, along with thousands of containers of radioactive waste, were purposely thrown into the ocean."

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Causes and Effects of Ocean Pollution- Conservative Energy Future

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Causes and Effects of Ocean Pollution- Conservative Energy Future

# data[].attributes.body
LINK
-"The release of other chemical nutrients into the ocean’s ecosystem leads to reductions in oxygen levels, the decay of plant life, and a severe decline in the quality of the seawater itself. As a result, all levels of oceanic life, plants and animals, are highly affected."
-"The dumping of toxic liquids in the ocean directly affects marine life as they are considered hazardous, and secondly, they raise the temperature of the ocean, a phenomenon known as thermal pollution, as the temperature of these liquids is quite high. Animals and plants that cannot survive at higher temperatures eventually perish."
-"Often, this water picks up man-made, harmful contaminants that pollute the ocean, including fertilizers, petroleum, pesticides and other forms of soil contaminants. Fertilizers and waste from land animals and humans can be hugely detrimental to the ocean by creating dead zones."
-"Besides, many ships lose thousands of crates each year due to storms, emergencies, and accidents. This causes noise pollution (excessive, unexpected noise that interrupts the balance of life, most often caused by modes of transportation), excessive algae, and ballast water."

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Raising Awareness of Plastic Waste- The New York Times

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Raising Awareness of Plastic Waste- The New York Times

# data[].attributes.body
LINK

# data[].attributes.body
"Marine pollution is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide."

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Image

stockphoto-graf/shutterstock

Marine pollution is a growing problem in today's world. Our ocean is being flooded with two main types of pollution: chemicals and trash.

Chemical contamination, or nutrient pollution, is concerning for health, environmental, and economic reasons. This type of pollution occurs when human activities, notably the use of fertilizer on farms, lead to the runoff of chemicals into waterways that ultimately flow into the ocean. The increased concentration of chemicals, such as nitrogen and phosphorus, in the coastal ocean promotes the growth of algal blooms, which can be toxic to wildlife and harmful to humans. The negative effects on health and the environment caused by algal blooms hurt local fishing and tourism industries.

Marine trash encompasses all manufactured products-most of them plastic-that end up in the ocean. Littering, storm winds, and poor waste management all contribute to the accumulation of this debris, 80 percent of which comes from sources on land. Common types of marine debris include various plastic items like shopping bags and beverage bottles, along with cigarette butts, bottle caps, food wrappers, and fishing gear. Plastic waste is particularly problematic as a pollutant because it is so long-lasting. Plastic items can take hundreds of years to decompose.

This trash poses dangers to both humans and animals. Fish become tangled and injured in the debris, and some animals mistake items like plastic bags for food and eat them. Small organisms feed on tiny bits of broken-down plastic, called microplastic, and absorb the chemicals from the plastic into their tissues. Microplastics are less than five millimeters (0.2 inches) in diameter and have been detected in a range of marine species, including plankton and whales. When small organisms that consume microplastics are eaten by larger animals, the toxic chemicals then become part of their tissues. In this way, the microplastic pollution migrates up the food chain, eventually becoming part of the food that humans eat.

Solutions for marine pollution include prevention and cleanup. Disposable and single-use plastic is abundantly used in today's society, from shopping bags to shipping packaging to plastic bottles. Changing society's approach to plastic use will be a long and economically challenging process. Cleanup, in contrast, may be impossible for some items. Many types of debris (including some plastics) do not float, so they are lost deep in the ocean. Plastics that do float tend to collect in large "patches" in ocean gyres. The Pacific Garbage Patch is one example of such a collection, with plastics and microplastics floating on and below the surface of swirling ocean currents between California and Hawaii in an area of about 1.6 million square kilometers (617,763 square miles), although its size is not fixed. These patches are less like islands of trash and, as the National Oceanic and Atmospheric Administration says, more like flecks of microplastic pepper swirling around an ocean soup. Even some promising solutions are inadequate for combating marine pollution. So-called "biodegradable" plastics often break down only at temperatures higher than will ever be reached in the ocean.

Nonetheless, many countries are taking action. According to a 2018 report from the United Nations, more than sixty countries have enacted regulations to limit or ban the use of disposable plastic items.

National Geographic Society

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Marine pollution is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide.

# data[].attributes.headline
Tracking Marine Pollution by John E. Elliott and Kyle H. Elliott

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Tracking Marine Pollution by John E. Elliott and Kyle H. Elliott

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"Visit a beach almost anywhere and
you will see plastic waste floating
in the water and heaped above the
tide lines."

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The Impact of Ocean Noise Pollution on Marine Biodiversity by Linda S. Weilgart, Ph.D.

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The Impact of Ocean Noise Pollution on Marine Biodiversity by Linda S. Weilgart, Ph.D.

# data[].attributes.body
"Noise levels are steadily rising, so ocean noise must be managed both
nationally and internationally in a precautionary way before irreversible damage to biodiversity and the marine ecosystem occurs. "

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Ocean Pollution Knowledge & Actions by Delaney Smith 

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Ocean Pollution Knowledge & Actions by Delaney Smith 

# data[].attributes.body
"It was found that ocean pollution education and reducing personal waste guidance can help raise awareness because it can positively impact individuals' environmental attitudes and actions."

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Why scientists say ‘plastivores’ could be the solution to plastic pollution by Liz Tung 

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Why scientists say ‘plastivores’ could be the solution to plastic pollution by Liz Tung 

# data[].attributes.body
"contamination by dirt and other plastics makes it difficult to fully break down the plastic. Another is that the process of mechanical recycling causes the plastic to degrade, meaning that the resulting product is of worse quality."

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The promise of 'plastivores'

But what if there were a way to break plastic down to its constituent parts - parts that would either not be harmful to the environment, or could be reused to make new plastics?

As it turns out, there is something that has that ability, but it's not some kind of solvent, or chemical process - it's a life form called "plastivores."

"Individual organisms that use plastic as their primary carbon and energy source," Erickson said. "So they can live off of nothing but plastic, which is pretty wild to think about."

In 2016, Japanese scientists discovered the first plastivores in the form of a bacterium that was able to survive solely on PET bottles.

"The reason I say that's kind of wild to think about is that plastic, PET, was invented in the 1940s - I think, early 1940s," Erickson said. "So that's not very long for an organism to decide that that's a good, tasty meal."

The discovery kicked off an international race among scientists to identify the key to this bacterium's success: the enzymes, or proteins, that are responsible for breaking the plastic down.

Since then, the research on plastivores has expanded in all directions, including the recent discovery of our first animal plastivore: the humble wax worm.

Looking for wax worms' secret weapon

Canadian biologist Christophe Lemoine said a European team made the discovery in 2017, entirely by accident.

"Kind of the funny story behind that is that one of the team members is actually a beekeeper," Lemoine said. "And what happened is that she was just cleaning her hive and found some of those wax worms, put them in a plastic bag, wrapped them up, put them on the kitchen counter, and a couple of hours later, the wax worms were happily sneaking their way out of the plastic bag. So that's kinda what put the wax worm on the international scene."

The big mission after that discovery was figuring out what the mystery enzyme or enzymes were that allowed wax worms to break plastic down.

Lemoine, who'd been studying the effects of microplastics on animal physiology, teamed up with an insect biologist to find out how exactly wax worms were able to digest plastic. It was, in other words, a different version of the same mission other scientists have been on - zeroing in on the magic formula for breaking plastic down.

"Our goal was to try to decipher whether it was the bacteria or the wax worm that was doing that stuff," Lemoine said. "So essentially trying to figure out if the bacteria was really mostly responsible for the other plastic breakdown, the polyethylene breakdown, or if it was the worm."

In March of last year, Lemoine and his colleagues released a study with the beginnings of an answer. It showed that the wax worm's digestive microbes were the bigger factor in their ability to break down plastic - but it also showed that the microbes on their own didn't work as efficiently as they did in the guts of the wax worm.

"We're still pursuing that question," Lemoine said, "trying to figure out what is this synergy between the bacteria and the wax worm that allow them to really accelerate this breakdown of plastic."

An ambitious bid to scale up enzyme recycling

The ultimate goal with all of this research is to isolate the enzyme - the secret sauce, if you will - that's responsible for achieving that breakdown, improving it, and hopefully applying it on an industrial scale.

Most of the scientists I talked to said we're still years away from making that a reality - except for one: French biochemical engineer Alain Marty.

"We are now building a demo plant and it will be in operation in September 2021," Marty said. "And after this, the idea is to have a first industrial plant in 2024."

Marty is the chief science officer for a French company called Carbios, which last year announced that it had synthesized an enzyme capable of breaking down PET 10,000 times faster than the bacterium discovered by Japanese scientists.

Marty described the enzyme and its substrate as a lock and a key. His job, along with his group, was to improve the lock (the enzyme) so that it better fit the key (the PET). And, Marty said, they've been successful. When the group started in 2015, it took several weeks to degrade just 2% to 3% of PET. But today, the best result has been to degrade 90% in 10 hours.

Not only that, Marty said, they're able to break the plastic down to its constituent elements, pure enough to reform plastic of equal quality to the original.

Carbios has already scored investment from major companies like L'Oreal and PepsiCo, Marty said, and the goal is to open recycling plants around the world, capable of handling 100,000-200,000 tons of plastic every year.

Part of a bigger solution

But some scientists caution that although these developments are exciting, they aren't a solution - at least not yet.

"This cannot be the main idea," said environmental microbiologist Hermann Heipieper. "These processes are very, very expensive so far and need to be supplemented."

Heipieper should know: Last year, he led a group of German researchers in discovering a strain of bacteria capable of degrading key building blocks of polyurethane, another widely used plastic that's particularly difficult to recycle.

But when asked about the promise of enzymes like the ones Marty or his team have uncovered, Heipieper instead points to other solutions.

"One thing is clear - we cannot go on as we do," Heipieper said, referring to the pervasiveness of single-use plastic. "The main thing must be that we stop using crude oil-based plastics."

Secondly, Heipieper said, scientists should lobby legislators to encourage that we switch over to different, more degradable plastics.

Heipieper isn't alone in this approach.

In September 2020, the NREL group Erika Erickson and Brandon Knott are a part of put out a study describing the second of two key enzymes capable of breaking PET down. But they, too, are cautious about the discovery's potential.

"We should be really excited about the advances that are being made in terms of enzymes breaking down PET," Knott said. "But there are lots of different types of plastics, and we need solutions to recycle and upcycle all of them. Enzymatic degradation of PET is one piece."

There's no one solution, Knott said. We need ways of degrading and reusing all different kinds of plastic - and of inventing new plastics with end-of-life in mind. And maybe most importantly, we need to decrease our plastic use in general.

At the same time, we have to remember that plastic waste isn't just wrappers and straws - in places like the Guinean village where Erickson lived, it's health, clean water, and resources and workforce hours that would all need to be replaced.

"The social aspects of this are also really important," Erickson said. "We can come up with new technologies, but we can't necessarily create a technology to save ourselves. We kind of have to do that from the ground up."

# data[].attributes.attachment_link.title
Why scientists say 'plastivores' could be the solution to plastic pollution

# data[].attributes.attachment_link.description
But what if there were a way to break plastic down to its constituent parts - parts that would either not be harmful to the environment, or could be reused to make new plastics? As it turns out, there is something that has that ability, but it's not some kind of solvent, or chemical process - it's a life form called "plastivores."

# data[].attributes.headline
Molecular Biomarkers: Their significance and application in marine pollution monitoring by A. Sarkar, D. Ray, Amulya N. Shrivastava, Subhodeep Sarker

# data[].attributes.subject
Molecular Biomarkers: Their significance and application in marine pollution monitoring by A. Sarkar, D. Ray, Amulya N. Shrivastava, Subhodeep Sarker

# data[].attributes.body
"The measurement of the levels of DNA integrity in marine organisms such as Sea stars (Asterias rubens)
from the North Sea and the marine snails (Planaxis sulcatus) from the Arabian Sea along the Goa coast exposed to environmental xenobiotic contaminants clearly indicated the extent and the nature of pollution at the sampling sites
along coastal environment."

# data[].attributes.headline
Contaminants in Tracked Seabirds Showing Regional Patterns of Marine Pollution by Atsuo Ito, Rei Yamashita, Hideshige Takada, Takashi Yamamoto, Kozue Shiomi, Carlos Zavalaga, Tomoya Abe, Shinichi Watanabe, Maki Yamamoto, Katsufumi Sato, Hiroyoshi Kohno, Ken Yoda, Tomohiko Iida, and Yutaka Watanuki

# data[].attributes.subject
Contaminants in Tracked Seabirds Showing Regional Patterns of Marine Pollution by Atsuo Ito, Rei Yamashita, Hideshige Takada, Takashi Yamamoto, Kozue Shiomi, Carlos Zavalaga, Tomoya Abe, Shinichi Watanabe, Maki Yamamoto, Katsufumi Sato, Hiroyoshi Kohno, Ken Yoda, Tomohiko Iida, and Yutaka Watanuki

# data[].attributes.body
"All were lowest in birds foraging
in the Pacific. This distribution of POPs concentration partly agrees with previous findings based on mussels, fish, and seawater and
possibly reflects the mobility and emission sources of each type of POP. These results highlight the importance of information on the
foraging area of highly mobile top predators to make them more effective monitors of regional marine pollution."

# data[].attributes.headline
Global ecological, social and economic impacts of marine plastic (Nicola J. Beaumont, Margrethe Aanesen, Melanie C. Austen, Tobias Börger, James R. Clark, Matthew Cole, Tara Hooper, Penelope K. Lindeque, Christine Pascoe, Kayleigh J. Wyles)

# data[].attributes.subject
Global ecological, social and economic impacts of marine plastic (Nicola J. Beaumont, Margrethe Aanesen, Melanie C. Austen, Tobias Börger, James R. Clark, Matthew Cole, Tara Hooper, Penelope K. Lindeque, Christine Pascoe, Kayleigh J. Wyles)

# data[].attributes.body
- "A novel translation of these ecological impacts into ecosystem service impacts provides evidence that all ecosystem services are impacted to some extent by the presence of marine plastic, with a reduction in provision predicted for all except one. This reduction in ecosystem service provision is evidenced to have implications for human health and wellbeing, linked particularly to fisheries, heritage and charismatic species, and recreation."

- "A solid understanding of the ecological, social and economic impact of marine plastic is necessary to inform a global transition in the way we make, use and reuse plastic, in such a way as to eliminate negative impacts, with implications for public behaviour, legislation and governance, industry and commerce (Pahl et al., 2017)."

- "...there is global evidence of impact with medium to high frequency on all subjects, with a medium to high degree of irreversibility. The majority of these impacts are negative with the exception of algae and bacteria. In this case the plastic increases the range of habitats available for colonisation and enables the spread of these species to new areas, thus increasing their range and abundance."

- "The results show all ecosystem services are impacted to some extent by the presence of marine plastic..."

- "Marine ecosystem services comprehensively contribute to human wellbeing, meaning that their reduction will endanger the continued welfare of human societies, especially in coastal communities (Naeem et al., 2016)."

- "Marine plastic has the potential to reduce the efficiency and productivity of commercial fisheries and aquaculture through physical entanglement and damage (Mouat et al., 2010), but also by posing a direct risk to fish stocks. Plastic is frequently ingested by a wide range of marine species, including those directly vital to food provision such as shellfish and fish (Rochman et al., 2015) at all stages of their lifecycle (Steer et al., 2017; Lusher et al., 2012)."

- "Images and articles describing beached whales and seabirds with stomachs full of plastic are prevalent in mainstream media (Reuters, 2017). Such charismatic marine species hold significant value to humans, and there is extensive evidence that humans experience wellbeing in the knowledge that marine animals are there and will remain for future generations, even if they never directly experience them... The substantial public attention on the impact of plastic on iconic marine species suggests that even single incidents can have strong and detrimental wellbeing impacts and that the relationship between ecosystem impact and human wellbeing loss is not necessarily linear."

- "These results supported the ecosystem service analysis in finding plastic to have a substantial negative impact on experiential recreation... Litter on the shore is disliked (Hartley et al., 2013), and is often stated as a key reason why visitors will spend less time in these environments or will avoid certain sites if they anticipate it will be littered (Anderson and Brown, 1984; Ballance et al., 2000; Tudor and Williams, 2006; WHO, 2003). This has a range of economic costs, from clean-up expenses to loss of tourism revenue."

- "As well as having economic costs, the presence of litter can also have direct consequences on individuals' physical and mental health. Visitors and maritime workers are susceptible to a range of injuries... Spending time at littered coastlines has also been demonstrated to be detrimental to their mood and mental wellbeing (Wyles et al., 2016). In turn, refraining from going to the coast due to these risks, can also have health implications, inhibiting the opportunity to reap the benefits coastlines typically offer, e.g. promoting physical activity, facilitating important social interactions such as strengthening family bonds, and improving physical and mental health (Ashbullby et al., 2013; Papathanasopoulou et al., 2016)."

- "...the presence of plastic has the potential to dramatically shift the ecology of marine systems (Galloway et al., 2017). An altered environment and shifts in biodiversity can have potentially wide-reaching and unpredictable secondary societal consequences (Worm et al., 2006)."

- "...although the results show increased bacterial and algal colonisation and abundance, this might have a negative effect for the wider ecosystem. Marine plastic is an attractive substrate that is quickly and intensively colonised by a wide range of opportunistic species... Colonisation of plastic provides a mechanism for movement of organisms between biomes, thus potentially increasing their biogeographical range and risking the spread of invasive species and disease (Lamb et al., 2018). Indeed, marine plastic has been linked to increased rates of invasive species and unprecedented rates of species dispersal using man-made flotsam have been documented, including an estimate that marine plastic has doubled organisms' opportunities for dispersal in the tropics (Barnes, 2002). This additional impact is not included in this analysis, but has clear potential for causing substantial ecological, social, and economic consequences."

- "Drawing on our analysis, we recommend a systematic global research agenda for the recording and reporting of marine plastic research, especially relating to the most vulnerable and valuable ecosystem services, and on the potential contamination of the human food chain. It is also recommended to undertake further research on the heterogeneity and timescale of impacts to enable the efficient development of future policy and regulation."

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Highlights

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Marine plastic has a global impact on all ecological subjects reviewed.

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There are negative impacts on the provision of almost all marine ecosystem services.

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Negative human wellbeing impacts, particularly fisheries, heritage, recreation.

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Economic costs conjectured: $3300-$33,000 per tonne of marine plastic per year.

Abstract

This research takes a holistic approach to considering the consequences of marine plastic pollution. A semi-systematic literature review of 1191 data points provides the basis to determine the global ecological, social and economic impacts. An ecosystem impact analysis demonstrates that there is global evidence of impact with medium to high frequency on all subjects, with a medium to high degree of irreversibility. A novel translation of these ecological impacts into ecosystem service impacts provides evidence that all ecosystem services are impacted to some extent by the presence of marine plastic, with a reduction in provision predicted for all except one. This reduction in ecosystem service provision is evidenced to have implications for human health and wellbeing, linked particularly to fisheries, heritage and charismatic species, and recreation.

View Abstract

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Global ecological, social and economic impacts of marine plastic

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Marine plastic has a global impact on all ecological subjects reviewed. * There are negative impacts on the provision of almost all marine ecosystem services. * Negative human wellbeing impacts, particularly fisheries, heritage, recreation. * Economic costs conjectured: $3300-$33,000 per tonne of marine plastic per year.

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Marine Pollution in the United States by Donald F. Boesch, Richard H. Burroughs, Joel E. Baker, Robert P. Mason, Christopher L. Rowe, Ronald L. Siefert

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Marine Pollution in the United States by Donald F. Boesch, Richard H. Burroughs, Joel E. Baker, Robert P. Mason, Christopher L. Rowe, Ronald L. Siefert

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"Toxic pollutants, including pesticides, industrial organic chemicals and trace metals, are widespread contaminants of the marine environment. But they produce discernible adverse effects on ecosystems only in limited areas around population centers and ports. Some of these chemicals are known through experimental studies to affect the reproductive, immune, or endocrine systems of marine organisms at low concentrations, and may have subtle effects on marine organisms and populations over a broader area."

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Marine Pollution in the United States

Prepared for the Pew Oceans Commission by

Donald F. Boesch
University of Maryland Center for Environmental Science

Richard H. Burroughs
University of Rhode Island

Joel E. Baker
University of Maryland Center for Environmental Science

Robert P. Mason
University of Maryland Center for Environmental Science

Christopher L. Rowe
University of Maryland Center for Environmental Science

Ronald L. Siefert
University of Maryland Center for Environmental Science

Abstract

Direct discharges of pollutants into the ocean and coastal waters from sewage treatment plants, industrial facilities, ships, and the at-sea dumping of sewage sludge and other wastes have been greatly reduced over the past 30 years as a result of the Clean Water Act and other federal statutes. Advances in waste treatment have kept ahead of increases in the volume of wastes, and that trend is likely to continue. Some persistent toxic pollutants, such as DDT and PCBs, were banned for manufacture or use in the United States, and ambient levels of these pollutants have been decreasing in most U.S. marine environments. On the other hand, pollution from land runoff went largely unabated during this period; in some cases it has increased. As a result, diffuse sources now contribute a larger portion of many kinds of pollutants than the more thoroughly regulated direct discharges.

Toxic pollutants, including pesticides, industrial organic chemicals and trace metals, are widespread contaminants of the marine environment. But they produce discernible adverse effects on ecosystems only in limited areas around population centers and ports. Some of these chemicals are known through experimental studies to affect the reproductive, immune, or endocrine systems of marine organisms at low concentrations, and may have subtle effects on marine organisms and populations over a broader area. While some of the most toxic substances have been banned for manufacture and use, material previously released may remain in the environment for decades to centuries. High

Nutrient Overenrichment

The dominant form of plant life in the world's oceans is free-floating, single-celled algae known as phytoplankton. Like all plants, phytoplankton need nutrients-- nitrogen, phosphorus, and other minerals--and light to grow and reproduce. Most of the needed nutrients either wash into the ocean from the land or move from the deeper waters to the surface through upwelling.

The growth of phytoplankton is usually limited by the availability of nutrients. Nitrogen is the nutrient that is usually in the shortest supply. But if nitrogen becomes abundant, the growth of phytoplankton can increase dramatically. An explosive increase in the population of phytoplankton is known as an algal bloom. A bloom often contains more phytoplankton than can be eaten by marine animals. The uneaten algae--and wastes from animals that eat the algae--sink to the ocean bottom, and decompose.

Through the process of decomposition, the dissolved oxygen levels in the water near the bottom can decrease substantially.

The long-term increase in the supply of organic matter to an ecosystem--often as a result of excess nutrients, or nutrient overenrichment--is called eutrophication.

Eutrophication creates two harmful effects: oxygen depletion and reduced water clarity. When dissolved oxygen levels drop to levels that equal two milligrams per liter or less, a condition called hypoxia occurs.

Anoxia refers to a complete absence of dissolved oxygen in the water.

More mobile marine animals, like fish and crabs, can often migrate out of hypoxic areas. Other animals--such as oysters and marine snails--that lack mobility or cannot move quickly enough to escape hypoxia may suffocate. When water clarity is reduced by greater concentrations of algae, less light can penetrate to the ocean bottom where seagrasses and seaweeds live. As a result, these plants may sicken and die.

Increased nutrient levels in surface water (rivers and streams) and in groundwater from the land can be attributed to human activity. Major sources of nitrogen, phosphorus, and other nutrients delivered to the oceans include discharges from wastewater-treatment plants, runoff and groundwater from cropland, urban and suburban stormwater (runoff from paved surfaces), farm animal wastes, and even nutrients found in airborne emissions from power plants, automobile exhaust, and industrial smokestacks.

concentrations of persistent contaminants in bottom sediments require careful consideration when removed by dredging or managed in place.

Overenrichment of coastal ecosystems by nutrients, particularly nitrogen, has emerged as the most widespread and measurable effect of pollution on living marine resources and biodiversity in U.S. coastal waters. Excessive nutrient levels (overenrichment or eutrophication; see sidebar on these pages) may result in serious depletion of the dissolved oxygen supplies needed by marine animals, loss of habitat (e.g., seagrasses and coral reefs), and algal blooms. Two-thirds of the surface area of estuaries and bays in the conterminous U.S. suffers one or more symptoms of overenrichment. Because a majority of the nutrients in most regions now come from diffuse sources rather than direct discharges, reversing coastal eutrophication will require management strategies for watersheds reaching far inland from the coastal environment. Feasible measures include advanced treatment of municipal wastewaters, reduction of nitrogen oxide emissions from power plants and vehicles, control of ammonia emissions from animal feedlots, more efficient use of fertilizers and manure, and restoration of wetlands and floodplains that act as nutrient traps.

I. Introduction

This report provides background on the effects of pollution on life in the ocean and coastal waters of the United States for the Pew Oceans Commission, which is conducting a national dialogue on policies needed to restore and protect living marine resources. Pollution occurs when a substance, an organism, or energy (e.g., sound or heat) is released into the environment by human activities and produces an adverse effect on organisms or the environmental processes on which they depend.

Marine pollution comes in many forms and from many sources (Table 1). Some pollutants in sufficient concentrations are toxic to marine organisms. These include both naturally occurring chemicals present in much higher concentrations as a result of human activities (e.g., trace metals and oil) as well as compounds that did not exist in nature until manufactured by humans (e.g., pesticides such as DDT).

Other pollutants are harmful not because they are toxic but because they stimulate biological activity or alter habitats. The addition of large amounts of organic matter in the form of sewage or fish-processing wastes, for example, supports the growth of decomposer microbes that can exhaust the available oxygen supply. Inputs of nutrients (particularly forms of nitrogen and phosphorus), while responsible for the rich biological productivity of many coastal waters, can stimulate the production of more organic matter than an ecosystem can assimilate. Turbid waters, depletion of oxygen, and blooms of noxious algae may result. Sediments from land runoff or from dredging can decrease water clarity and smother sensitive bottom habitats such as reefs and seagrass beds.

Pollution emanates from either direct discharges or diffuse sources. Land-based industrial and municipal outfalls discharge wastewater into coastal waters or rivers that drain to the coast. Other direct discharges include those from vessel operations and at-sea waste disposal. Pollutants from diffuse sources include those released into the atmosphere by fossil-fuel and waste combustion; and land runoff of pesticides, toxic-waste products, nutrients, and sediments. Although chemical contaminants--released as a result of human activities--can now be found throughout the worlds oceans, most demonstrable effects on living resources occur in coastal waters and are the result of pollution from land.

The report first reviews accomplishments in reducing marine pollution, and then highlights the need for further reductions in the effects of toxic substances and nutrients as remaining major challenges. Diffuse sources of pollution via land runoff and atmospheric deposition are particularly important and have proved difficult to control. To provide grounding for policies needed to restore and protect living marine resources, the report: describes the forms, sources, movements, and effects of pollutants; assesses past and future trends of pollution in the U.S.; considers additional steps that could reduce pollution; and places pollution threats into a broader context of other threats to living resources.

II. Reductions of Pollution

Municipal and Industrial Discharges

In 1972, Congress passed the landmark Federal Water Pollution Control Act, which was reauthorized in 1977, 1981, and 1987 as the Clean Water Act (CWA). The goal of the law is to eliminate pollution in the nations waters. It imposes uniform minimum federal standards for municipal and industrial wastewater treatment based on best available technology. Facilities discharging wastes at discernible points are required to obtain permits from the U.S. Environmental Protection Agency (EPA) or from state pollution-control agencies. Permits include enforceable limits on pollutants in the discharges, and require dischargers to conduct monitoring and to file reports when limits are violated.

Most publicly owned treatment works (POTWs) handle industrial wastes as well as domestic sewage. Because discharges of untreated organic wastes had degraded many rivers, lakes, and coastal waters by depleting dissolved oxygen and causing fish kills, the Clean Water Act required POTWs to achieve at least "secondary" treatment. Secondary treatment adds biodegradation of the organic matter in the wastewater to the solids (sludge) removal and disinfection included in "primary" treatment. Consequently, it significantly reduces the biological oxygen demand (BOD) of wastewater effluent. The CWA provided substantial amounts of money to help pay for the required POTW improvements. About 125 billion dollars have been spent in constructing or expanding POTWs, mainly between 1972 and 1992 when federal grants provided three-quarters of the costs (NRC, 1993a). Waivers to this requirement were allowed for several deep ocean outfalls where it could be demonstrated that the organic wastes would not harm the environment. Additional waste treatment, such as reduction of suspended solids, was often required.

Technology-based standards and the National Pollutant Discharge Elimination System (NPDES) have resulted in a dramatic reduction in the amount of pollutants entering U.S. waters, including coastal waters. Reductions in discharges of organic matter improved conditions in the Delaware River estuary near Philadelphia to the point that low oxygen levels no longer prevent the upriver migration of juvenile striped bass and American shad (Weisberg et al., 1996). Oxygen levels in New York Harbor are approximately 50 percent higher (NRC, 1993a). The most thoroughly documented example of the benefits of improved treatment may be the Southern California Bight, off Los Angeles and San Diego (Box 1), where inputs of many pollutants have been reduced 90 percent or more over a 25-year period. Kelp beds, fish and invertebrate communities, and certain seabird populations have greatly, if not completely, recovered. These improvements have been accomplished despite a steady increase in population and in the volume of wastewater discharged.

Another long-term effort to restore water quality has recently come to fruition with the completion in September 2000 of a new deepwater outfall for treated effluents from the Boston region. The offshore discharge into Massachusetts Bay will result in improvements in environmental quality in Boston Harbor beyond those already achieved as a result of the cessation of sludge disposal, reductions in combined sewer overflow, and secondary treatment of

Wastes from the nations largest metropolitan center (17 million people) are discharged into a bight of the Pacific Ocean via deepwater (about 200 feet) outfalls. Pollution from publicly owned treatment works (POTWs) has been reduced significantly since the 1970s even though the population served and wastewater volumes grew steadily (Schiff et al., 2000; Figure 1). This reduction was accomplished through source control, pretreatment of industrial wastes, reclamation, and treatment-plant upgrades, including secondary or other advanced treatment (concentrating on chemical removal of suspended solids). Capital improvements to POTWs throughout the Southern California Bight cost more than five billion dollars.

Discharges from POTWs of most pollutants into the bight have decreased: 50 percent for suspended solids and biological oxygen demand, 90 percent for combined trace metals, and more than 99 percent for chlorinated hydrocarbons. Bight sediments show a record of decreasing contamination. Concentrations of contaminants in fish and marine mammals have declined. Kelp beds near the POTWs have returned. The extent of degraded bottom communities has contracted by about two-thirds; and the incidence of tumors and other maladies in bottom fish has returned to background levels.

A unique problem for the bight is the fact that large quantities of the pesticide DDT were previously discharged, particularly through the Los Angeles Countys POTW. This facility received wastes from the worlds largest DDT manufacturer. In 1971 an estimated 440,000 pounds of DDT were discharged via an outfall off Palos Verdes. Today, only 3 pounds of DDT are discharged from all Southern California POTWs combined (Schiff et al., 2000). Concentrations of DDT and its degradation products have declined greatly in fish and marine mammals. Populations of brown pelicans, which were decimated by the eggshell thinning induced by DDT contamination, have rebounded. However, brown pelicans, bald eagles, and peregrine falcons are still being affected by the residual DDT contamination in the bottom sediments of the bight. Although this "legacy" contamination is slowly being buried, some DDT is still remobilized into the food chain.

wastes. Although recovery is far from complete, liver tumors in flounder are less common, mussels accumulate lower levels of organic contaminants, and bottom invertebrate communities are recovering in the harbor (Rex, 2000). Field studies and computer models predict that moving the discharge offshore to deeper waters will not increase concentrations of pollutants, including nutrients, in Massachusetts Bay.

Although secondary treatment of municipal sewage removes at least 85 percent of the organic material and suspended solids in wastewater, only one-third of the nitrogen and phosphorus is eliminated (NRC, 1993a; NRC, 2000a). These two nutrients are the principal causes of eutrophication of receiving waters (see Section IV). Advanced treatment technologies, capable of eliminating up to 97 percent of the nitrogen and 99 percent of the phosphorus (NRC, 2000a), are being implemented in regions susceptible to nutrient overenrichment from direct discharges.

Pollutant levels have also been reduced in discharges from industries, including oil and gas production, refineries, chemical manufacturing, electric-power generation, and food processing. Although regionally important, industrial discharges contribute a relatively small portion of pollutant loadings on a national scale. Industrial discharges often have specific waste-reduction requirements that necessitate pollution prevention (elimination or reduction of the source in the industrial process), recycling and reuse, and advanced waste treatment.

Pollution from aquaculture--effluents from ponds or holding tanks on land and materials released from net pens and shellfish racks or rafts--is receiving new regulatory attention with the expansion of aquaculture in coastal waters. Pollutants include uneaten food, fecal and excretory material, and releases of antibiotics, pesticides, hormones, anesthetics, pigments, vitamins, and minerals. Organic deposits under net pens and shellfish rafts often alter the bottom habitat and affect seabed communities in the immediate vicinity. Extensive aquaculture operations can constitute a major source of nutrient inputs to the smaller bays and estuaries in which they are located. Antibiotic, pesticide, and hormone releases can also affect wild organisms in the region (Goldburg and Triplett, 1997).

Additional reductions of pollution from direct discharges will undoubtedly be required and more effective source controls and treatment technologies developed to meet those requirements. Two forces are driving these reductions. First, the Clean Water Act requires dischargers to implement advanced pollution controls where conventional technology is not sufficient to protect aquatic life and the human uses assigned to the water body receiving the discharge. Standards for designated uses are not currently met for one-third of U.S. waters (EPA 2000a). In such cases, the Clean Water Act specifies that total maximum daily loads (TMDLs) be determined and allocated among point and nonpoint sources. Second, ever-closer scrutiny is given to the inputs of chemicals that induce toxicity at very low concentrations, persist in the environment for long periods, and reach high levels of accumulation in the tissues of fish and wildlife.

Vessel Discharges

Pollutants are discharged to the ocean from the routine operations of ships and boats (including discharges of sewage and industrial-processing wastes and the release of petroleum hydrocarbons from engine exhausts and bilge and ballast waters). Vessel-related pollution may also occur as a result of accidental spills and solid-waste disposals.

At-sea release of oily water has been an international issue over the past 30 years and is regulated under the International Convention for the Prevention of Pollution from Ships. Compartments of oil tankers are typically filled with seawater for ballast when emptied of their cargo. Some ports, such as Port Valdez, Alaska, have ballast-water treatment facilities. Although ballast-water discharges may cause problems along some tanker routes and are responsible for tar balls that contaminate the surface of high seas, they comprise a relatively small percentage of oil pollution in the marine environment (NRC, 1985). Exhaust emissions into the water from smaller vessels may be a significant source of petroleum hydrocarbons in more confined coastal waters.

Atmospheric emissions from ships are being recognized as a significant source of global air pollution (Corbett and Fischbeck, 1997), yet they are not subject to the same restrictions for protection of air quality as are land-based power plants and manufacturers. Seagoing vessels are responsible for an estimated 14 percent of emissions of nitrogen from fossil fuels and 16 percent of the emissions of sulfur from petroleum uses into the atmosphere (Corbett and Fischbeck, 1997).

Cruise ships, although not a major source of pollution to U.S. coastal waters as a whole, can cause problems in areas such as Caribbean island harbors, which accommodate intense cruise-ship activity, or relatively pristine areas such as the inland passages of Alaska. Cruise ships generate sewage, gray water, solid wastes, oily wastes, and waste from photo processors, swimming pools and dry cleaners. (EPA, 2000b).

Ocean Dumping

The practice of transporting wastes for disposal in the ocean became a cause for national and international concern in the 1970s (CEQ, 1970). The Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matters, or the London Dumping Convention, came into force in 1975, acknowledging through its regulatory framework that different materials have vastly different impacts on the marine environment. Nationally, ocean disposal in U.S. waters has been regulated under the Marine Protection, Research, and Sanctuaries Act of 1972 (MPRSA) by a permit procedure that prohibits dumping of some materials, establishes criteria to authorize dumping of others, and identifies sites for disposal. The Clean Water Act also regulates discharges into the territorial sea and navigable waters of the United States. In the ten years following passage of the MPRSA, dumping of industrial waste, construction debris, solid waste, and incineration of chemicals remained low, but dumping of sewage sludge doubled (Burroughs, 1988). Although the amount of dredged sediment disposed in coastal waters remained constant, it was approximately an order of magnitude greater in volume than the sludge dumped (Figure 2).

During the 1980s, public apprehension about ocean dumping grew. Sewage sludge dumped in the New York Bight was blamed for an apparent decline in water quality and health risks to bathers. Controversy also erupted over ocean incineration of chemical wastes in the Gulf of Mexico. In 1988, Congress enacted the Ocean Dumping Ban Act that prohibited ocean dumping of sewage sludge and industrial chemicals. Sewage sludge must now be incinerated, disposed of on land, or reused--alternatives that have their own set of environmental impacts, including pollution of the marine environment via land runoff and atmospheric deposition.

Today, virtually all the material dumped into coastal and marine waters is bottom sediment removed by dredging (Figure 2). Under the Clean Water Act, the U.S. Army Corps of Engineers issues permits for disposal of dredged material, subject to guidelines established by EPA. Protocols have been developed to determine whether dredged sediments are suitable for placement in the ocean or coastal environment. These protocols involve an assessment based on the sediment characteristics, contaminant levels, the toxicity of contaminants present, and the potential for the contaminants to accumulate in the tissues of organisms (EPA, 1991). Based on these criteria, dredging may not be permitted at all or the dredged sediments may be deemed unacceptable for overboard disposal. Placement in a landfill, in a confined disposal facility, or in a contained underwater disposal site is then required. Approximately five to ten percent of the sediments dredged require management as contaminated sediments (NRC, 1997).

Although the federal laws governing dredged material disposal have eliminated the practice of discarding heavily contaminated harbor sediments in the marine environment, they have not eliminated controversies. Despite the protections afforded by regulatory requirements and testing protocols, significant controversies surround the overboard disposal of dredged sediments that are deemed acceptably "clean." These controversies are related in part to the physical impacts of dredged sediment placement, including increased turbidity, siltation, burial of bottom organisms, and permanent changes in the quality of bottom habitat. In addition, the public, resource users, and environmental managers are concerned that contaminants in the dredged sediment will be mobilized and made more bioavailable by overboard disposal. As a result, many ports struggled to resolve impasses in selecting and permitting alternatives for dredged sediment placement (Box 2). On one side, there is an aversion to placing wastes of any kind into the ocean and coastal waters; on the other, there are constraints related to costs, limits in the feasibility of beneficial uses, and opposition to disposal alternatives outside of the marine environment.

The volume of commerce moving through U.S. ports is increasing and will continue to do so because of increased world trade and dependence on foreign

Navigation channels and berths in San Francisco Bay tend to fill in rapidly because of the large amount of mobile sediments in the bay--a legacy of placer mining following the California Gold Rush--and strong tidal currents. Dredged sediments were typically placed back into the bay, mostly at a site near Alcatraz Island, where strong tidal currents dispersed them. However, disposal of large quantities of sediments generated from channel deepening changed the current patterns at the Alcatraz site so that sediments placed there no longer dispersed.

The limitations of this site, the lack of readily available alternatives, public concerns, lawsuits, and fragmented agency management coalesced to create an impasse, or so-called mudlock, that halted most dredging. This caused significant problems for both commercial and military shipping. The U.S. Navy, citing national security requirements, broke the impasse by dumping dredged sediments at a deepwater site in the ocean. Subsequently, EPA designated an ocean disposal site to receive sandy sediments dredged by federally funded projects.

In 1990, federal, state, and regional agencies joined with navigation interest groups, fishing groups, environmental organizations, and the public to develop a Long-Term Management Strategy for Bay Area dredged material (U.S. Army Corps of Engineers, 1998). The strategy emphasizes a balance between ocean disposal and beneficial reuse at upland/wetland sites with limited in-bay disposal. During a transitional period, the amount of dredged material deposited at in-bay sites would be reduced from 80 percent to 20 percent, while upland sites, reuses, and wetland restoration are developed. Toxicity testing and monitoring would be bolstered. Nonetheless, environmental interest groups are calling for the elimination of in-bay disposal altogether.

energy resources (Bureau of Transportation Statistics, 2000). This is driving a trend toward larger ships with deeper drafts and, thus, continued pressure for deeper channels. Although there has been an effort to develop a national policy for screening dredged material and evaluating disposal options (Maritime Administration, 1994), the U.S. lacks a coherent port development policy that is compatible with the environmental quality objectives articulated in federal environmental statutes.

Diffuse Sources of Pollution

In most U.S. coastal regions, diffuse sources of pollution--including land runoff and atmospheric deposition--are now responsible for most serious water-quality problems (EPA and USDA, 1998). Because of the reduced loadings of many contaminants achieved by point-source controls, land runoff is currently the dominant source of many contaminants in both the Southern California Bight and Chesapeake Bay (Figure 3).

Except where the manufacture or use of a contaminant has ceased or changed dramatically--such as for DDT and some other pesticides, PCBs, or lead additives in gasoline--the contribution of diffuse sources of pollution in coastal and ocean waters has not been significantly reduced by the programs implemented over the last 30 years. Moreover, loadings of some pollutants from diffuse sources, such as nitrogen (Howarth et al., 1996; Goolsby et al., 2000) and mercury (Swain et al., 1992), appear to have increased during that time period.

The importance of diffuse sources of pollutants has long been recognized. There are provisions in the Clean Water Act and Coastal Zone Management Act intended to achieve reductions in pollution of coastal waters from diffuse sources. Nonetheless, improvements have been slow and difficult. This is due to the diversity of diffuse sources, resistance to regulatory solutions, and the multiple pathways through which the pollutants may reach coastal and ocean environments.

Fallout from the atmosphere is an important and previously under-appreciated source of a number of important pollutants, including nitrogen, lead, mercury, and organochlorine compounds such as DDT and PCBs (Box 3). Some of these pollutants can be transported over long distances before falling onto the ocean or on watersheds draining to the coast. Atmospheric transport is the primary mechanism for contamination of oceanic regions remote from human activities, such as polar seas and the open ocean. In a recent report to Congress, the EPA (2000c) indicated that atmospheric deposition of PCBs, banned and restricted pesticides, and lead has been declining in recent years for the Great Lakes and some coastal waters, but that deposition of other pollutants such as nitrogen has not fallen off.

Contaminants and nutrients in runoff are influenced by: (1) land uses, i.e., whether the land is forested, agricultural, industrial or urban; (2) human activities that involve the purposeful or unintended placement of fertilizers, pesticides, atmospheric contaminants, and wastes on the land surface; and (3) natural phenomena and land-use decisions that affect water infiltration, retention, groundwater movement, runoff, and transport in streams and rivers.

Sediments that erode from the land and reach the coast in runoff carry various contaminants bound to sediment particles, including trace metals, organic compounds, and phosphorus. The sediments themselves can constitute a serious form of pollution, silting up shallow water environments, increasing the need for dredging, altering benthic habitats, and decreasing water clarity. Alternatively, improved soil conservation practices and the entrapment of riverine sediments behind dams have resulted in decreased delivery of sediments to many U.S. coastal environments over the last half century (Meade, 1982). For some coastal environments, this has improved the conditions for living resources by increasing water clarity and decreasing sedimentation; however, other coastal ecosystems, such as sandy beaches and subsiding deltas (Milliman, 1997), are experiencing problems because a continued supply of sediments is needed to sustain them.

Atmospheric deposition of pollutants involves a variety of physical processes that transport chemicals to the Earths surface (Baker, 1997; Figure 4). Wet deposition involves processes by which gases and airborne particles are washed from the atmosphere during precipitation. Dry deposition results from the impact of fine particles (aerosols) on surfaces and on gas exchange at terrestrial and aquatic surfaces. The magnitude of atmospheric deposition depends directly on the concentration of pollutants in the atmosphere, the form of each chemical (gas or particulate), the size of the aerosol particles, and the extent of precipitation and physical mixing.

Pollutants are introduced into the atmosphere from a variety of sources, travel through several pathways, and reach various fates. Materials such as soot, NO X, and SO ₂, are released from natural sources (forests, volcanoes, and fires) as well as from human activities (anthropogenic sources). However, many atmospheric pollutants (e.g., PCBs, CFCs) are only derived from anthropogenic sources. Sources of air pollutants are commonly categorized as stationary (e.g., power plants, refineries, and incinerators), mobile (vehicles, aircraft, locomotives, and ships), or area (e.g., volatilization of ammonia from manure).

The lifetime of a pollutant in the atmosphere is dependent on its chemical reactivity and its partitioning among gas, liquid, and solid phases. In general, chemicals on particles or in liquid water have a shorter lifetime in the atmosphere and are not transported far from their source, while gaseous chemicals may remain in the atmosphere a long time and travel great distances. Persistent chemicals that are revolatilized after being deposited can travel like a grasshopper over great distances. Because these chemicals are more prone to evaporation under warmer temperatures, they tend to be redistributed to higher latitudes (Wania and Mackay, 1996).

Atmospheric deposition is an important source of nitrogen, some trace metals (e.g., lead and mercury), and organochlorine compounds (e.g., DDT and PCBs) to coastal and ocean environments:

Lead emissions to the atmosphere in the U.S. and Europe are now orders of magnitude lower than in the early 1970s due to ending the use of leaded additives to gasoline. The impact can be seen in the reduction of lead concentrations in surface waters of the open ocean (Wu and Boyle, 1997), coastal sediments (Bricker, 1993; Cochran et al., 1998; Hornberger et al., 1999), and shellfish tissues (Lauenstein and Daskalakis, 1998).

The global reservoir of atmospheric mercury has increased by a factor of two to five since the beginning of industrialization (Boening, 2000) and is dominated by anthropogenic emissions (Mason et al., 1994). Principal sources (>80 percent) are combustion processes, primarily coal burning and municipal and medical-waste incineration (EPA, 1997). Higher mercury concentrations in wet deposition are found in urban areas, reflecting local power plant and incinerator sources (Mason et al., 2000). Surface waters of the North Atlantic have higher mercury concentrations compared to the equatorial Pacific (Mason and Fitzgerald, 1996), probably as a result of long-distance transport of gaseous forms of mercury from sources in North America.

The discovery of organochlorine pesticides such as DDT and industrial chemicals such as PCBs in the waters and biota of the Arctic and Antarctic ecosystems fundamentally altered our view of the role of the atmosphere in distributing pollutants on a global scale (Wania and Mackay, 1996).

Conversion of lands to urban and suburban uses has been proceeding at a rate far greater than the rate of population growth in many coastal communities as a result of the U.S. tendency for low-density residential development (sprawl). The conversion of previously undisturbed land surfaces that allowed the infiltration and slow release of water to impervious surfaces such as roofs, driveways, roads, and parking lots results in higher peak runoff, which carries greater pollution loads and alters the salinity balance in bays and estuaries during both wet and dry weather periods.

While direct discharges still contribute significant toxic contaminants and nutrients to coastal waters, it is clear that protecting the marine environment from the many adverse effects of pollution will require more effective control of land runoff and atmospheric deposition--now the principal sources of the most damaging pollutants in many coastal ecosystems.

III. The Challenge of Toxic Contaminants

Nature of Toxic Contaminants

Toxic pollutants include trace metals (e.g., cadmium, copper, lead, and mercury), a variety of biocides (e.g., DDT, tributyl tin) and their by-products, industrial organic chemicals (e.g., PCBs and tetrachlorobenzene), and by-products of industrial processes and combustion (e.g., polycyclic aromatic hydrocarbons, or PAHs, and dioxins). Those pollutants meriting greatest attention are widespread and persistent in the environment, have a propensity to accumulate in biological tissues, or induce biological effects at extremely low concentrations.

The historic use of some compounds no longer manufactured or used in the United States--like DDT, PCBs, and lead additives in gasoline--has left a legacy of contamination. Generally, legacy contaminants in U.S. coastal environments have declined. However, these compounds are still in use in other countries and they continue to run off the land. For example, it has been estimated that less than 10 percent of the total lead deposited from the atmosphere onto the Sacramento and San Joaquin river basins has yet been delivered to San Francisco Bay (Steding et al., 2000). As the concentrations of some heavy metals and organochlorine compounds decrease in the marine environment, other contaminants are still being released and do not show a clear downward trend. Some may even be increasing. For example, analyses of lake and reservoir sediments show increasing levels of PAHs associated with suburban development (Van Metre et al., 2000). PAHs come from multiple sources, including petroleum and the combustion of fossil fuels and biomass, some of which have been reduced (e.g., coal coking) and some of which continue (e.g., urban runoff and atmospheric deposition of combustion by-products).

Humankind will be dealing with legacy contaminants of the marine environment well into the future. Repositories of persistent contaminants in marine sediments can be sources of long-term exposure to marine life well after the inputs of these contaminants have largely ceased. Examples of this include DDT in the Southern California Bight (Box 1) and PCBs in San Francisco Bay (San Francisco Estuary Institute, 1996). The deep sea may be the final sink for some persistent organic pollutants (Looser et al., 2000).

Biological Effects

Toxic effects, both lethal and sublethal, have been extensively documented in laboratory experiments, but concrete examples of contaminant effects on populations of marine organisms are limited (McDowell et al., 1999). Key issues considered here include the potential for bioaccumulation of toxicants by marine life; the effects of disruptions of organisms immune, endocrine, and reproductive systems on their populations; and the effects on marine communities of chronic exposure to the high concentrations of contaminants found in coastal sediments.

Organisms may accumulate contaminants from water, sediments, or food in their tissues. This can result in concentrations of the contaminant many times higher than those found in the environment. The degree of bioaccumulation depends on the level of exposure and the mechanisms by which the organism expels, stores, or metabolically breaks down the contaminant. Compounds such as organochlorine pesticides and PCBs tend to accumulate in fatty tissues (lipophilic compounds), where they may remain for long periods of time. Animals in the upper levels of the food web may accumulate these compounds from prey until lipid storage sites are saturated. Their metabolism is then challenged to degrade and excrete the contaminants or their metabolic by-products, some of which are much more toxic than the original form. In this way, highly persistent and bioaccumulative compounds can magnify through the food web, having little noticeable toxic effect except at the highest trophic levels. Trace metals are also subject to bioaccumulation, but except for metal-containing organic compounds (e.g., methyl mercury) do not biomagnify in marine organisms.

Bioconcentration and biomagnification of toxicants pose particular risks to predators of fish, including birds, marine mammals, and humans. High concentrations of toxicants, such as PCBs and mercury, necessitate health advisories for frequent consumers of fish in some regions (EPA, 1999). Perhaps the most widely recognized effect of persistent contaminants on marine populations is the decline of populations of bald eagles and brown pelicans during the 1960s and 1970s. DDT and its breakdown products accumulated in adult birds from their prey, leading to changes in calcium metabolism in breeding females. The birds produced abnormally thin eggshells and ultimately experienced reproductive failures (Hickey and Anderson, 1968; Blus et al., 1971).

Extensive evidence demonstrates that toxicants can disrupt the metabolic, regulatory, or disease defense systems of an organism, eventually compromising its survival or reproduction. For example, genetic damage, malformations, and reduced growth and mobility were observed in Pacific herring embryos exposed to PAH (from weathered oil) levels as low as 0.7 ppb (Carls et al., 1999). Mollusks exposed to PCBs in New Bedford Harbor, Massachusetts, experienced both a loss of reproductive output and increased susceptibility to disease (McDowell et al., 1999). Accumulation of PCBs and PAHs in Puget Sound rock sole has been correlated with reductions in spawning success (Johnson et al., 1998). Bioconcentration of PCBs has also been linked with impaired immune defenses that lead to disease and death in marine mammals, including seals and dolphins (Kuehl and Haebler, 1995).

Particular attention is currently being devoted to the disruption of endocrine systems by toxic contaminants. Some organochlorine pesticides, PCBs, dioxins, and other compounds functionally mimic or alter the production of hormones (NRC, 1999b). Tributyl tin (TBT), a biocide used in antifouling paints, has been shown to disrupt hormones controlling sexual development in mollusks exposed to concentrations as low as 10 parts per trillion, leading to irreversible reproductive abnormalities (e.g., females developing male sex organs) and reproductive failures (NRC, 1999b). Significant declines in marine snail populations have been documented in regions of North America and Europe where use of TBT was intense (Matthiessen and Gibbs, 1998; Nehring, 2000). Most uses of TBT paints in the U.S. were discontinued as a result of these findings. Feminization of males due to exposure to estrogen mimics and masculinization of females exposed to estrogen blockers have been observed in various animals, including mollusks, fish, reptiles, birds, and mammals (NRC, 1999b; Royal Society, 2000). For example, endocrine-disrupting chemicals have been implicated in the incidence of hermaphroditism in Norwegian polar bears and St. Lawrence beluga whales (De Guise et al., 1994).

Toxic substances in sediments appear to have localized effects in U.S. bays and estuaries and in certain offshore regions that received wastes, such as the New York and Southern California Bights. In the past decade, EPAs Environmental Monitoring and Assessment Program (EMAP) and National Sediment Quality Survey and NOAAs National Status and Trends Program have extensively measured the concentrations of contaminants in bottom sediments in the nations bays and estuaries, collected collateral data on the communities of benthic organisms living in those sediments, and assayed toxicity of sediments to sensitive amphipod crustaceans. Using these three components--contaminant concentrations (and their probable effects based on an extensive database), the health of the communities living in the sediments, and experimental toxicity--Long (2000) concluded that biologically significant chemical contamination and toxic responses occurred throughout the nations coastal waters, especially in the most urbanized and industrialized regions. Chemical concentrations exceeding guidelines for probable effects occurred in 26 percent of samples, representing 7.5 percent of the bays and estuaries surveyed. Generally, sediments proved toxic to the crustaceans where contaminant concentrations were high and benthic communities degraded.

This three-pronged approach involving field studies does not fully resolve which contaminants and other factors are actually responsible for the toxicity and community degradation. The synergistic, additive, or antagonistic interactions among contaminants are poorly understood and challenging to assess, thus making it difficult to predict biological responses simply based on knowledge of the types and concentrations of contaminants present in a given area (Yang, 1998).

Pollution Abatement and Remediation

The most effective way to reduce the harmful impacts of toxic contaminants on marine ecosystems is to eliminate or restrict their use or production. The experiences with lead additives in gasoline, DDT, and PCBs show that in the long term this approach can reduce environmental concentrations and exposure for marine organisms. In addition to discontinuing the use or production of these substances, source controls, recycling and reuse, and other forms of "pollution prevention" provide the first line of defense (NRC, 1993a). Treatment and removal of pollutants from effluents and atmospheric emissions provide a second line of defense. Improved knowledge of the fate and effects of various classes of compounds and screening processes for new chemical products have reduced, but not totally eliminated, the risk of "surprises" such as DDT, PCBs, and TBT.

Legacy contaminants must be managed for decades to centuries into the future. Options include control of losses from waste sites and contaminated soils on land, treatment of urban stormwater, and remediation of contaminated sediments. Contaminated sediments exist in many ports, where they pose a risk of reintroduction of toxicants into the water column by physical disturbance of sediments or transferal through the food chain. Options for managing contaminated sediments include: leaving them in place to allow recovery to proceed through degradation and burial, capping them with clean sediments, treating them in place, and removing them for containment or treatment (NRC, 1997).

In the case of the pesticide kepone in the James River estuary, Virginia, the decision was to leave the contaminated sediments in place, and subsequent reductions of contaminants levels in the ecosystem and organisms were observed (NRC, 1997). However, when contaminant levels are high and the risks of reintroduction are great, capping may speed recovery of the ecosystem. The EPA has proposed placing clean sediments atop portions of the DDT deposits off Palos Verdes, California, in order to test the feasibility and effectiveness of this remediation method. Representatives of the DDT manufacturer have criticized this method because DDT concentrations in surface sediments have been declining and the process may expose heavily contaminated sediment below the surface (Whitaker, 2000). A similar controversy surrounds proposals to cap the dredged sediment disposal site in the apex of the New York Bight. These cases exemplify the dilemma faced in making decisions regarding remediation of contaminated sediments.

IV. The Challenge of Nutrient Pollution

Nutrient Overenrichment

An increase in the supply of organic matter in a water body is termed eutrophication (Nixon, 1995; see sidebar in Abstract). Over the last 30 years the discharge of organic wastes from municipal and industrial sources declined as a result of improved treatment. At the same time, eutrophication in many areas became more extensive due to increased loadings of mineral nutrients, particularly nitrogen and phosphorus, which stimulate the production of organic matter within the marine ecosystem. There are many consequences of this increased organic production, both beneficial and harmful. The latter include hypoxia, or stressfully low dissolved oxygen, reductions of seagrass beds and corals, and, potentially, noxious or toxic blooms of algae.

Nutrient pollution has been increasingly recognized as a key threat to coastal environments over the past 20 years because of both new scientific understanding and declining trends in water quality (Nixon, 1995). Loadings of nitrogen flowing in rivers to the Atlantic and Gulf coasts of the United States have increased four to eight fold from the time of European colonization (Howarth et al., 1996). Most of that increase came in the last half of the 20 th century. Scientific research has demonstrated that nutrient overenrichment was a major contributor to the extensive changes observed in coastal ecosystems during that period. Three recent scientific assessments addressed nutrient pollution in U.S. coastal waters.

The National Oceanic and Atmospheric Administration characterized the symptoms of eutrophication for 138 bays and estuaries around the U.S. coast based on data review and expert consultations (Bricker et al., 1999). Approximately one-third of the water bodies had high expressions of eutrophic conditions (Figure 5). Altogether, 82 water bodies, representing 67 percent of the combined surface area of these bays and estuaries exhibited moderate to high degrees of depleted dissolved oxygen, loss of seagrasses, or harmful algal blooms. Moreover, it was predicted that eutrophic conditions would become more severe in 86 of these ecosystems by 2020. Systems having low inflow, poor flushing, or strong stratification are particularly susceptible to eutrophication. While this assessment was limited to estuaries and bays in the conterminous states, nutrient pollution has also resulted in loss of coral reef habitat and seagrasses in U.S. tropical regions (Bell, 1992; Lapointe, 1999).

In a large region of the inner continental shelf off the coast of Louisiana and Texas, the bottom water oxygen levels fall too low (<2 mg/L) to support fish, crustaceans, and many other invertebrates during the warmer months of April to September. This hypoxic zone, or Dead Zone, has been as large as 12,000 square miles (20,000 km ²) but varies in dimensions from year to year and within years, depending on river runoff, and meteorological and oceanographic factors. A recently completed integrated assessment conducted under the auspices of the Presidents National Science and Technology Council (CENR, 2000) concluded that:

1. the hypoxia is caused primarily by excess nutrient runoff (particularly of nitrogen) from the Mississippi-Atchafalaya River Basin in combination with stratification of Gulf waters;

2. landscape alterations and river channelization during the late 19th century and first half of the 20th century reduced the river basins hydrologic buffering capacity;

3. eutrophication and hypoxia increased during the latter half of the 20th century during which the flux of nitrate-nitrogen almost tripled (between 1955-1970 and 1980-1996), concomitant with the rapid increase in the use of chemical fertilizers;

4. about 90 percent of the nitrate load comes from diffuse sources, particularly from agricultural lands along the upper Mississippi and Ohio rivers, nearly 1000 miles upstream from the rivers mouth; and

5. Gulf ecosystems and fisheries are affected by hypoxia, but economic impacts are difficult to quantify.

Models predicted significant reductions in hypoxia would occur with a 20 to 30 percent nitrogen load reduction. Two approaches are required to achieve that level of reduction: (1) improved agronomic practices that reduce nitrogen losses from farm fields and (2) trapping nitrogen lost from fields in restored wetlands, vegetated buffers, reconnected floodplains, and coastal wetlands. These recommendations have been met with considerable controversy regarding both the certainty of the science and the costs and impacts on food production among midwestern states and agricultural interests. In October 2000, a task force including senior policymakers from eight federal agencies, nine states, and two tribal governments set a general goal to reduce the average area experiencing hypoxia to less than 5,000 km 2 (1,930 square miles or about 40 percent of its average dimensions during the 1990s), which the task force recognized would probably require the reduction of nitrogen inputs by 30 percent.

The Presidents National Science and Technology Council produced an integrated assessment of large-scale hypoxia in the northern Gulf of Mexico (CENR, 2000) (Box 4). The assessment concluded that diffuse sources of nutrient pollution have caused more extensive hypoxia, covering up to 12,000 square miles of the northern Gulf continental shelf, since the 1950s. It identified more efficient use of fertilizers and restoration of wetlands in the river basin as effective means to reduce the extent and severity of hypoxia in the Gulf.

Finally, the National Research Council (2000a) recently published an in-depth evaluation of the causes and effects of overenrichment in coastal waters and of abatement strategies, including monitoring and modeling, goal setting, and source reduction and control. Noting the substantial adverse impacts of nutrient pollution and the likelihood that nutrient loads will increase as human populations grow, the NRC calls for a nationwide strategy for reducing impairment by nutrient pollution and protecting unimpaired waters. One goal suggests a 10 percent reduction by the year 2010 in the number of coastal water bodies demonstrating severe impacts and a 25 percent reduction by 2020.

Large-scale eutrophication has also occurred in seas around other developed nations, including the Baltic Sea, eastern North Sea, northern Adriatic Sea, northwestern Black Sea, and Japans Seto Inland Sea. As in the U.S., these problems also developed during the last half of the 20 th century with expanded use of chemical fertilizers and combustion of fossil fuels. Coastal eutrophication is but one dimension of the significant modification of the nitrogen cycle (Vitousek et al., 1997). Globally, the amount of biologically available nitrogen added to the biosphere each year has more than doubled the amount made available by the natural sources of plant fixation and lightning. In addition to impacts on marine ecosystems, acid rain, loss of forest soil fertility, emissions of nitrous oxide (a greenhouse gas), and reduction of plant biodiversity are other consequences of the increasing flow of biologically available nitrogen in the biosphere.

Consequences for Living Marine Resources

Nutrients are generally in short supply in most ecosystems and microscopic and macroscopic plants have adapted mechanisms to assimilate them and grow when they are available. The addition of nutrients to an ecosystem affects not only how fast plants grow but also which plants grow most rapidly. These responses are affected by many factors, including light, temperature, mixing and stratification of the water column, the ratio of the various nutrients, and grazing by animals. In marine ecosystems, the rate at which plants create new organic matter (primary production) is closely related to nitrogen inputs (NRC, 2000a). Primary production doubled from the beginning of the 1960s to 1990 in the southern Kattegat between Denmark and Sweden (Richardson and Heilman, 1995), one of the few areas where primary production has been consistently measured. Similar dramatic increases in primary production in the Chesapeake Bay (Cooper, 1995) and the northern Gulf of Mexico (Rabalais et al., 1996) have been inferred based on chemicals and fossils laid down in bottom sediments.

Although much of the increased organic matter is consumed by zooplankton, bacteria, and bottom filter feeders, the amount of organic matter that falls to the bottom in the form of dead plant cells and fecal matter from grazing organisms is also increased. This changes the food regime of organisms living on the bottom or within bottom sediments, initially increasing the abundance of animals and microorganisms that consume the rich organic deposits. However, the respiration of these decomposer organisms consumes oxygen. At first oxygen is depleted in bottom sediments and, if organic loading is heavy enough, the deficit of oxygen reaches into the water column above the seabed. The severity and persistence of resulting hypoxia depend on the stratification of the water column. Less dense (warmer or fresher) surface waters overlying more dense (colder or saltier) bottom waters, with little mixing between the layers, prevents supplies of oxygen from surface waters from replenishing the oxygen consumed by decomposers.

Severe hypoxia near the bottom has become a more regular and extensive seasonal phenomenon in ecosystems such as the Louisiana continental shelf (Rabalais et al., 1996), Chesapeake Bay (Boesch et al., in press), the western basin of Long Island Sound (Long Island Sound Study, 1998), and many other parts of the world (Diaz and Rosenberg, 1995).

As bottom oxygen is depleted, many organisms unable to swim away succumb. Crustaceans, echinoderms, and mollusks are particularly sensitive to the lack of oxygen and the hydrogen sulfide that emanates from putrefying sediments. Consequently, benthic communities experiencing eutrophication and hypoxic stress are altered and have less species diversity. Substantial changes in the production and composition of benthic communities may be evident well before severe hypoxic conditions occur in overlying waters (Diaz and Rosenberg, 1995).

Hypoxic conditions in waters above the seabed force fish and swimming invertebrates to avoid the stressful conditions. Catches of fish and shrimp in bottom trawls in the Gulf of Mexico are dramatically lower or nonexistent where bottom dissolved oxygen levels fall below 2 mg/L (CENR, 2000). Fish and crustaceans often move up in the water column, where they are more susceptible to predation. Hypoxia can also block normal onshore-offshore migration. Despite these apparent obstacles to survival, large-scale hypoxia has not decimated the important shrimp fisheries of the northern Gulf of Mexico (CENR, 2000), although it may have reduced the catch of brown shrimp (Zimmerman and Nance, in press). Many other factors affect shrimp populations, rendering less-than-catastrophic effects due to hypoxia difficult to detect. Bottom hypoxia has resulted in declines in the catches in demersal (living near the bottom) fisheries in Europe and Japan (Caddy, 1993, 2000).

Nutrients are necessary to support the productivity of marine food webs. Across the full range of marine ecosystems, the supply of nutrients--particularly nitrogen--is positively correlated with fisheries yield (Nixon et al., 1986). Although the general relationship is undeniable, the strength of coupling between nutrients and the production of animals within a given ecosystem has been called into question (Micheli, 1999). Nonetheless, increases in the catch of some fisheries have been observed in the North and Baltic Seas and Seto Inland Sea in Japan, concurrent with increases in nutrient loading (Caddy, 1993). While some increases are attributable to increased fishing pressure or more efficient fishing paralleling increased nutrient loadings, greater yields appear to be at least in part due to nutrient stimulation of the food chains supporting the fisheries. Other factors can affect fisheries yield, however, including climatic variation and the effects of fishing itself on the food chain. There is a strong global trend of "fishing down the food chain," wherein fishing is targeted on smaller species once stocks of higher predators are depleted (Pauly et al., 1998). Under these conditions there is less predation on mid-trophic level species, allowing them to become more abundant. These factors may result in increased yields measured as biomass, but the economic value of the fishery is typically smaller.

Eutrophication combined with increased fishing intensity, results in higher yields of small pelagic (living in the water column) species and reduced yields of top

predators and demersal (living near the bottom) species (Figure 6). In the extreme case, severe hypoxia and highly enriched food chains favor gelatinous predators (jellyfish and comb jellies) and result in the virtual elimination of demersal resources and reduction in small pelagic fish stocks (e.g., anchovies in the Black Sea). European seas can be ordered based on relative harvests of demersal and pelagic fisheries from the Irish Sea, with low nutrient inputs and proportionally greater demersal fisheries, to the Adriatic and Black Seas, with high nutrient inputs and predominantly pelagic fisheries (Caddy, 2000). In the U.S., enriched systems such as the Chesapeake Bay and northern Gulf of Mexico exhibit high yields of a small pelagic fish (menhaden). These systems have also experienced overharvesting of top predators such as striped bass, red snapper, and red drum and face current management problems for demersal crustaceans such as blue crabs and penaeid shrimp. The interactions between fishing pressure and eutrophication require that fisheries resources be managed not only in a multispecies context but also within an ecosystem framework. That framework may need to take into account human activities and natural processes extending even into the watersheds that deliver fresh water and nutrients to the sea (Caddy, 2000).

Seagrasses, seaweeds, and coral reefs create important habitats that provide food and shelter for a rich diversity of marine organisms, but are very sensitive to nutrient pollution. High nutrient levels in the water column can stimulate luxuriant growth of seagrass leaves, but there is insufficient rhizome growth to tide the plants over during periods of reduced photosynthesis. Reductions in available light caused by increased phytoplankton density and the proliferation of microscopic and macroscopic algae growing on seagrass blades also adversely affect the plants (Duarte, 1995). Seagrasses sometimes give way to fast growing macroalgae. Ultimately, conditions may become too turbid to support any macroscopic plants. As seagrass beds are lost, sediments are more easily eroded, causing the pace of loss to accelerate. Significant seagrass losses caused by excessive nutrient loadings have been observed in bays and coastal lagoons in New England, the mid-Atlantic region, Florida, Texas, and California (Bricker et al., 1999), as well as in Europe, Australia, and Japan (Duarte, 1995). On the other hand, partial recovery of seagrass beds in Sarasota, Tampa, and Chesapeake Bays has been observed as a result of efforts to abate nutrient pollution.

In the Baltic Sea, shallow rocky areas once covered with brown seaweeds that provide important spawning sites for fishes changed to a plant community dominated by rapidly growing green algae of little habitat value (Jansson and Dahlberg, 1999). In the northwestern Black Sea, an extensive meadow of red algae covering 4,000 square miles in the 1950s was reduced to 200 square miles by the 1990s, causing a loss of a harvested resource, the disappearance of a unique fauna, and reduction in an important source of oxygen (Zaitsev, 1999).

Reef-building corals have a symbiotic relationship with algae (zooxanthellae) that live in coral tissue and efficiently recycle available nutrients. This relationship allows corals to build reefs in clear waters with low nutrient levels. Even small increases in nutrient loads can stimulate phytoplankton and reduce light availability for zooxanthellae in the deeper parts of the reef. Elevated nutrient levels or reduced light availability may make already temperature-stressed corals more prone to expelling zooxanthellae, producing a "bleaching" effect (Brown, 2000).

Increased availability of nutrients can shift an ecosystem dominated by corals and coralline algae toward dominance by algal turf and macroalgae (Bell, 1992; Lapointe, 1999). Nutrient stimulation due to sewage additions was responsible for overgrowth of coral reefs by macroalgae in Kaneohe Bay, Hawaii, during the 1960s. Redirecting sewage out of the bay reversed this situation (Smith et al., 1981). Grazing animals normally prevent algal overgrowth, so when overfishing reduces grazers, reefs may be particularly susceptible to nutrient pollution (Lapointe, 1999). Overenrichment may also contribute to environmental stresses that make corals susceptible to diseases that appear to be increasing in distribution and virulence (Harvell et al., 1999). Finally, a recent study in Barbados found that boring sponges, which weaken coral structures, were more common in reefs experiencing eutrophication (Holmes, 2000).

Probably no effect of nutrient pollution has captured more public attention than harmful algal blooms, though, in fact, the causes of these blooms are complex and incompletely understood. Harmful blooms involve a variety of unicellular organisms that create nuisance conditions in high concentrations, cause mass mortalities of marine organisms, or illness--or even death--in humans (Smayda, 1997). Included are microscopic organisms (including red tides, brown tides, and the notorious phantom dinoflagellate, Pfiesteria piscicida) that result in shellfish poisoning of humans, cause fish kills, and jeopardize aquaculture operations. The distribution, incidence, and severity of harmful algal blooms have been rising in recent decades, not only in the United States but also in Europe, Japan, and China (Hallegraeff, 1993). While nutrient pollution is clearly not the cause of some blooms, in other cases there is evidence that changes in nutrient supplies and ratios are a contributing factor (NRC, 2000a).

The chemical form and relative ratios of available plant nutrients can cause shifts in phytoplankton composition and unusual algal blooms. Organic nitrogen seems to favor the organism causing brown tides and possibly Pfiesteria in mid-Atlantic bays. A shortage of silicon, a nutrient needed for diatom growth, relative to the supplies of nitrogen and phosphorus favors the growth of flagellated phytoplankton, some species of which are toxic (NRC, 2000a). Even if the species favored are not toxic, changes in the proportions of various nutrients delivered to coastal waters could change the type as well as the amount of phytoplankton that grows, with significant consequences throughout the food web. Inputs of silicon from land have declined in many regions as a result of sediment entrapment behind dams, while phosphorus inputs have remained steady and nitrogen inputs have increased (Justic et al., 1995; CENR, 2000).

Eutrophication usually results in reductions in species diversity of the affected ecosystems and, if extensive and severe, can impact biodiversity on a regional scale. In the northwestern shelf of the Black Sea, for example, only one-third as many benthic animal species could be found within a given depth zone in the 1980s as were found in the 1960s (Diaz and Rosenberg, 1995). There is at this point no evidence that eutrophication is threatening the global extinction of any species. However, by isolating distinct sub-populations, local extinction of a species in one or two estuaries along a coast could affect the genetic flow within the regional population (NRC, 1995).

Eutrophication can also adversely affect the services provided by marine ecosystems. Nutrient removal by denitrification and burial in bottom sediments may be one of the most important services provided by coastal ecosystems (Costanza et al., 1997). However, when severe seasonal hypoxia occurs, both phosphorus and ammonia are released from bottom sediments, turning an important sink for nutrient pollution into a source--thereby fueling more hypoxia (Boesch et al., in press). Through this and other feedback mechanisms, eutrophic ecosystems appear to be less resilient, i.e., they have less capacity to buffer changes and recover from disturbances more slowly.

Sources and Trends

Human activities have increased the flow of phosphorus to the worlds ocean by a factor of three over natural rates and the flow of nitrogen to U.S. coastal waters by four to eight times (NRC, 2000a). The largest human-controlled addition of nitrogen to the environment is the manufacture of inorganic nitrogen fertilizer. However, other activities, including the combustion of fossil fuels and cultivation of nitrogen-fixing crops, also convert atmospheric nitrogen into reduced, oxidized, or organic forms that are more biologically available than the gaseous nitrogen that comprises most of the air we breathe. About 20 percent of the fertilizer nitrogen applied in North America leaches into waters and 65 percent is removed in crops (NRC, 2000a). Most of the crops (70 percent) are fed to animals rather than humans; thus the amount of nitrogen reaching water bodies from animal wastes probably exceeds that from fertilizer runoff. Ammonia released into the air from animal wastes can be an important pathway though which nitrogen reaches coastal waters (Box 5). Human sewage is also an important avenue for nitrogen originally contained in crops or meat to reach coastal waters.

The relative importance of the sources of nutrients varies greatly among U.S. coastal regions, depending on the characteristics of their drainage basins, human populations, intensity of agricultural activities, and amount of atmospheric deposition. The percentages in Figure 7 are based on relating source estimates to fluxes measured through stream monitoring. Other statistical analyses across many watersheds (NRC, 2000a) suggest that atmospheric sources are a somewhat more significant contributor to diffuse source inputs than shown here, but the interregional differences depicted are in any case similar. Direct discharges of sewage dominate nitrogen inputs in northeastern bays; otherwise diffuse sources predominate. Agricultural sources generally are

Atmospheric deposition of nitrogen has been considered primarily in terms of the nitrogen oxides (NO X) produced by fossil-fuel combustion. However, recent evidence shows that ammonia emissions from agricultural operations can be a significant pathway for nitrogen inputs to coastal waters, accounting for as much as half of the total nitrogen deposition in regions with extensive livestock production (Walker et al., 2000).

In the Chesapeake Bay watershed, agricultural livestock contribute an estimated 81 percent of the annual atmospheric burden of ammonia (Chimka et al., 1997). Ammonia volatilizes from animal wastes in feeding operations, waste-storage facilities, and land application of manure. Increases in deposition of ammonia have occurred with expanding animal production. For example, a 60 percent increase in ammonia wet deposition was observed on the Delmarva Peninsula during the past two decades when this region experienced a 20-fold increase in poultry production (Scudlark and Church, 1999). In eastern North Carolina, ammonia wet deposition more than doubled over the same time period (Paerl and Whitall, 1999) in a region in which swine production tripled during the last ten years (Mallin, 2000).

Ammonia emissions also occur from various urban sources, including combustion, POTWs, and chemical plants. Recent modifications to gasoline-powered vehicles designed to reduce NOX emissions (i.e., three-way catalytic converters running rich air-fuel conditions) actually increase ammonia emission rates (Fraser and Cass, 1998).

most important from the Chesapeake Bay south, while atmospheric sources are greater than agricultural sources in the Northeast.

Although global additions of nitrogen to the biosphere are continuing to increase rapidly (Vitousek et al., 1997), current trends in nitrogen loadings to U.S. coastal waters are in aggregate generally stable or growing slowly (NRC, 2000a), while inputs of phosphorus are stable or declining. Although the worldwide use of chemical fertilizers is growing and projected to increase substantially to support an expanding world population and increased meat consumption (Forsberg, 1998), the use of chemical fertilizers in the U.S. nearly plateaued in the 1980s (NRC, 2000a). However, increased inputs of both nitrogen and phosphorus have occurred in regions of the country experiencing an expansion and intensification of animal-feeding operations or human population growth. Future consumption of fertilizers and generation of animal wastes in the U.S. could increase, depending on global market forces. Atmospheric deposition of nitrogen from combustion of fossil fuels in vehicles and power plants has stabilized over much of the country as a result of pollution controls imposed under the Clean Air Act, and future efforts to improve air quality should result in reductions (EPA, 2000c).

Population growth increases the amount of sewage generated--a problem for rapidly growing parts of the country. However, where eutrophication is a recognized problem, implementation of advanced nitrogen removal technologies in POTWs can keep pace with population increases. In many coastal regions of the U.S., however, the rate at which land that produces relatively little nutrient runoff is converted into suburban development, roads, and parking lots--which increase water and nutrient runoff--has been progressing much faster than that of population growth.

The NOAA national eutrophication assessment estimated that eutrophic conditions are likely to worsen in two-thirds of the bays and estuaries examined (Bricker et al., 1999). However, the prospect that emerges from the preceding analysis is not one of runaway increases in nutrient loading such as the nation experienced between 1960 and 1990, but one of stability or slower growth. This offers the real potential for substantial reductions with aggressive application of technologies. This outlook varies, of course, among regions, and coastal population growth near presently unaffected but susceptible bays and estuaries could greatly increase nutrient pollution in those areas. One should not infer from this that nutrient pollution is no longer a serious problem. The effects of eutrophication on coastal ecosystems are severe and widespread, making its abatement worthwhile, while at the same time challenging.

Pollution Abatement

Significant reduction in nutrient pollution may be achieved by approaches that: (1) reduce the use of the nutrients in the first place; (2) control losses to the environment at the point of release (e.g., farm field, animal feeding operation, lawn or subdivision, vehicle, power plant, or POTW); and (3) sequester or remove pollutants as they are transported to the sea.

Phosphorus can be almost completely removed from wastewaters by additional chemical and biological treatment. Phosphorus removal from discharges into the Potomac estuary below Washington, D.C., produced substantial improvements in water quality and living resources (Jaworski, 1990). Significant nitrogen removal has been achieved in Chesapeake, Tampa, and Sarasota Bays by biological nutrient Removal--a process in which one group of microorganisms convert wastewater ammonia to nitrate and another converts nitrate to nitrogen gas (NRC, 1993a, 2000a).

Reductions in nitrogen oxide (NO X) emissions to the atmosphere have been driven by air quality considerations generally outside the influence of water quality or coastal ecosystem managers. For example, in 1987 the Chesapeake Bay Program established a goal to reduce the controllable nitrogen inputs by 40 percent, but specifically excluded atmospheric deposition from the sources considered "controllable." Nitrogen oxide emissions from power plants and vehicles are regulated under the Clean Air Act (CAA); a key goal of the 1990 amendments of the act is to reduce ground-level ozone that poses human health risks and stresses forests and crops. Significant reductions in NO X emissions from stationary and mobile sources are in the offing to meet CAA requirements. The EPA estimates that a 40 percent reduction in NO X emissions can ultimately be achieved as a result of new standards, technologies, and efficiencies being pursued under the Clean Air Act. Atmospheric deposition of nitrogen may be far more "controllable" than previously thought.

Abatement of agricultural sources of nutrient pollution may prove to be a more difficult challenge. To be practical, abatement of agricultural sources of nutrients must focus not only on reducing fertilizer use but also on plugging the many leaks in agricultural nutrient cycles. Efficiencies in fertilizer use in U.S. agriculture, measured by the ratio of nitrogen in harvested crops to nitrogen in fertilizer applied, have been slowly but steadily increasing since the mid-1970s (Frink et al., 1999). Nevertheless, about one-third of the nitrogen applied is not recovered in harvested crops (NRC, 2000a). Not all of the missing nitrogen contributes to eutrophication of coastal waters. Much is denitrified in soils or aquatic systems en route to the sea or is stored in soils or groundwater. In addition to increasing the efficiency of nitrogen uptake by crops, the return of nitrogen gas to the atmosphere can be enhanced through management practices.

Various agricultural practices affect nitrogen and phosphorus runoff and losses to groundwater (which ultimately seeps into surface waters). Practices employed to reduce soil erosion, such as contour plowing, timing of cultivation, conservation tillage (little or no tilling), stream-bank protection, grazing management, and grassed waterways also reduce nutrient pollution. Other practices are more specifically targeted to the efficient use and retention of nutrients: (1) soil testing to precisely match fertilizer applications to crop nutritional needs (many farmers still overapply to ensure maximum crop yields); (2) applying fertilizer only at the time the crop needs it; (3) crop rotation; (4) planting cover crops in the fall; (5) using soil and manure amendments; and (6) specialized methods of application (NRC, 1993b, 2000a). Landscape practices such as maintaining buffer strips between cultivated fields and nearby streams, moderating excessive drainage by ditches and tile lines, and maintaining wooded riparian areas can further reduce the leakage of agricultural nutrients to surface waters. By combining these approaches a significant portion of the edge-of-field nitrogen losses can be reduced (Boesch and Brinsfield, 2000).

Often, animal wastes are the most significant source of nutrient pollution from agriculture. Although the total production of livestock in the U.S. has not dramatically increased in recent years, the number and size of concentrated animal feeding operations have. Enclosures or trapping devices may eventually be required to stem ammonia emissions from animal wastes. Manure management also presents a risk of pollution if holding facilities fail or do not function properly (Mallin, 2000). Finally, frequently too much manure is produced within a geographic area for it to be applied to near-by land without overloading soils with nutrients (NRC, 2000a).

Urban runoff can also be an important diffuse source of nutrients. Reduction and control of urban and suburban diffuse sources can be achieved through: (1) reductions in the use of fertilizers; (2) effective and well-maintained stormwater collection systems (retention ponds can remove 30 to 40 percent of the total nitrogen and 50 to 60 percent of the total phosphorus); and (3) improved septic systems that promote denitrification (NRC, 2000a). Preservation and restoration of riparian zones and streams within urban and suburban areas is also an important aspect of effective nutrient control. However, the ability of streams to function effectively in nutrient removal is compromised when a significant portion of their watersheds is covered by impervious surfaces and the amplified runoff scours the streambeds (Booth and Jackson, 1997).

Removing or sequestering pollutants as they are transported downstream can also abate nutrient pollution. Many American watersheds were once sponge-like, containing extensive floodplains and wetlands that slowed the flow of water and served as sinks for dissolved and suspended nutrients. However, well over half of the wetlands present in the conterminous United States at the time of European settlement have been converted to other land uses and the percentage of inland swamps and riparian wetlands lost is even greater (Mitsch and Gosselink, 2000). Many floodplains have been disconnected from their rivers by flood-control projects or agricultural conversion and no longer serve as nutrient sinks.

Reducing and controlling diffuse sources of land runoff must involve large-scale landscape management, including restoration of riparian zones and wetlands (NRC, 1999c). The integrated assessment of hypoxia in the Gulf of Mexico estimated that 5 million acres of restored wetlands in the Mississippi River Basin would reduce nitrogen loading to the Gulf by 20 percent. Coupled with feasible controls in agriculture, this would achieve a nearly 40 percent reduction in nitrogen delivered to the Gulf. Similarly, the Chesapeake Bay Program is striving to reforest 2,000 miles of riparian zones and restore 25,000 acres of wetlands by 2010 in order to achieve nutrient-reduction goals (Boesch et al., in press).

Geographically targeting riparian and wetland restoration is critical to its effectiveness in nutrient control. Statistical models based on water quality measurements throughout the Mississippi River Basin show that the percentage of nitrogen leached from a field that reaches the Gulf of Mexico depends greatly on its proximity to larger streams and rivers (Alexander et al., 2000). Biological uptake and denitrification are already effective in small watercourses; therefore restoration of riparian and wetland habitats along moderate to large streams should be more cost-effective. However, because of equity considerations, both incentives (subsidies and cost sharing, technical assistance, and insurance) and disincentives (regulatory controls, taxes, and fees) for abatement tend to be applied uniformly.

Watershed Approaches

A given body of coastal water (bay, estuary, or continental shelf region) receives nutrients from numerous sources; thus an integrated strategy for effective abatement of nutrient pollution is required. Because of the importance of diffuse sources, the strategy should encompass the catchment basin, or watershed, draining into the coastal waters. Moreover, it may have to consider nutrients originating outside the watershed but

Provisions of both the Clean Water Act (CWA) and Coastal Zone Management Act (CZMA) address diffuse, or nonpoint, sources of nutrient pollution; however, neither law has been very effective in controlling these sources. The implementation of provisions has been poorly funded, and arguably too much discretion is granted to states and local authorities (Adler, 1995; Johnson, 1999). A central programmatic shortcoming is the fundamental difficulty of influencing local land uses in order to obtain water-quality objectives. Under Section 208 of the 1972 CWA amendments, states were provided support and wide latitude in developing regional plans that identified point and nonpoint sources of pollution and methods, including land-use requirements, to control the sources (Anderson, 1999). However, the plans developed proved difficult to implement (Adler, 1995).

Section 319 of the 1987 CWA amendments requires the states to report on waters where nonpoint sources are problematic and identify best management practices and programs for source control. Section 319 moved toward, if not fully embraced, a watershed approach. State participation remained voluntary and EPA did not require states to penalize nonpoint-source polluters failing to adopt best management practices (Johnson, 1999). Lack of authority, enforcement, and monitoring clearly limited the effectiveness of the 319 efforts (Ruhl, 2000; Anderson, 1999).

In 1990 the reauthorized CZMA included Section 6217, under which states were required to implement enforceable policies to control nonpoint sources affecting coastal waters. Plans were originally required by 1995, but difficulties in implementation and coordination arose. Greater flexibility in plans was allowed and the period of implementation was extended to 15 years (NOAA, 2000).

Section 303 of the CWA requires the determination of a total maximum daily load (TMDL) of pollutants, including those from nonpoint sources, that can be accommodated by an impaired water body in order for it to meet water-quality standards for its designated use (Healy, 1997). A waste-load allocation then apportions the TMDL among the sources. This provision was not applied until lawsuits in the 1990s mandated EPA to establish TMDLs. Technical difficulties in determining TMDLs, legal issues regarding allocating loads among the sources, and the weak authority to regulate nonpoint sources remain serious barriers (Ruhl, 2000). Meanwhile, Congress prohibited EPA expenditures on further implementation of TMDLs during Fiscal Year 2001 (Copeland, 2000).

transported into it through the atmosphere. These are nonconventional units for ocean and coastal resource management and pose numerous challenges.

Recognition of the importance of diffuse-source pollution within a watershed is not new. Federal water-quality and coastal-management statutes include provisions for the assessment and control of nonpoint source pollution (Box 6), but to date they have been largely ineffective in limiting or reversing nutrient pollution of coastal waters. Their implementation has been long on planning and short on actions needed to control diffuse sources. In addition to the difficulties in determining management goals, acceptable nutrient loads, and efficient and equitable allocations among sources, substantial reliance on voluntary rather than mandatory reductions of diffuse sources has constrained the effectiveness of source-reduction efforts (NRC, 2000a).

These shortcomings are evidenced by the fact that 44 percent of the estuarine area assessed in 1998 did not fully meet the standards to support the designated uses (EPA, 2000a). Pathogens, organic enrichment, low dissolved oxygen, municipal point sources, urban runoff, and atmospheric deposition were the primary reasons, and diffuse-source pollution was a common culprit.

Concerted efforts to reverse nutrient pollution have been undertaken in some watersheds. In 1987 Pennsylvania, Maryland, Virginia, the District of Columbia, and the federal government committed to a 40 percent reduction in the "controllable" inputs of both nitrogen and phosphorus into the Chesapeake Bay by the year 2000. At about that same time, commitments were also being made for reductions of 50 percent of nutrient inputs into the North and Baltic Seas (Boesch and Brinsfield, 2000). Current estimates for the Chesapeake are that a 34 percent reduction in controllable phosphorus and a 28 percent reduction in controllable nitrogen will have been achieved by the end of 2000 (equivalent to 31 and 15 percent of the total loads, respectively; Blankenship, 2000). These are model simulations, but significant reductions in nutrient concentrations in rivers flowing into the Chesapeake Bay and in point-source discharges have been documented (Boesch et al., in press). These gains for the Chesapeake and European waters indicate that a watershed approach to reducing nutrient pollution can work, but so far successes have relied disproportionately on point-source controls. Under a new Chesapeake Bay agreement, more significant load reductions necessary to attain water-quality goals are being determined through a TMDL process (Box 6). Achieving these reductions will require a more rigorous effort to control diffuse sources.

Nitrogen inputs to Tampa Bay have also been reduced, again largely as a result of advanced treatment of sewage. Seagrass beds showed some recovery as a result (Lewis et al., 1998). A decrease in anthropogenic nitrogen inputs of 58.5 percent is the management goal for Long Island Sound (Long Island Sound Study, 1998). Direct discharges dominate nutrient sources there, thus biological nutrient removal at POTWs--at an estimated capital cost of more than 300 million dollars--is being counted on for most of this reduction.

Watershed approaches are being pursued in controlling diffuse sources of nutrients and other pollutants in many other U.S. bays and estuaries. In most, voluntary approaches to the pollution abatement are preferred; however, regulatory approaches are becoming more necessary, particularly as a result of the TMDL process (NRC, 2000a).

Watershed approaches place a premium on environmental modeling and monitoring (NRC, 2000a) in an adaptive management framework (Lee, 1993; CENR, 2000). Models are needed to track sources through the watershed, target abatement, and relate pollutant inputs to marine ecosystem responses. Monitoring is critical in determining the effectiveness of abatement strategies, evaluating responses of the ecosystem, and placing these responses in the context of ecosystem variability.

V. Implications for National Ocean Policy

Pollution in Context

Determining the degree to which pollution affects marine living resources, biodiversity, and ecosystem services and comparing these effects to those due to fishing, habitat modification, and global climate change are extremely difficult. Effects of pollution must be separated from those due to natural variability and other human activities. Furthermore, the broader consequences of sublethal or localized effects for populations and ecosystems are seldom clear. The ramifications for biodiversity and living resource production of localized toxic effects or even the more extensive effects of nutrient pollution are difficult to quantify.

For the most part, the effects of pollution are reversible and respond to pollution abatement. The exception may be when marine mammals and birds are endangered by mass mortalities or reproductive failures resulting from toxic contaminants. Recovery can, however, be problematic and recovery times long, particularly with regard to persistent contaminants and permanent landscape changes that affect the delivery of pollutants from the watershed.

The nations ocean and coastal ecosystems are being simultaneously affected by fishing activities (exploitation of target species, "bycatch," and effects of trawling), habitat modification from coastal development, and climate change, as well as by pollution. The relative importance of pollution as a threat to living resources depends on the region. Pollution is a fundamental concern in areas such as Boston Harbor, the northern Gulf of Mexico continental shelf, or the Chesapeake Bay. It is difficult to imagine environmental restoration and adequate resource management without controlling pollution. In other areas, pollution is much less a factor and habitat modification or fishing effects are far more important.

Most coastal ecosystems, in fact, experience multiple stresses. These stresses interact and, consequently, require integrated management solutions. Many coastal bays, for example, have been made less resilient to nutrient pollution because their oyster populations, which can filter out substantial amounts of organic matter, have been depleted. Furthermore, eutrophication will be influenced by the effects of climate change on freshwater runoff and water stratification (Justic et al., 1996; Najjar et al., 2000). And, overfishing of grazers makes coral reefs more susceptible to nutrient pollution (Lapointe, 1999). Multiple stresses can influence biodiversity on regional scales. For example, of 31 species of mammals, birds, and fish that have disappeared along the coast of the Netherlands over the past 2,000 years, 18 to 22 were as a result of overexploitation, 9 to 12 due to physical destruction of habitat, and 3 to 5 attributable to pollution (Wolff, 2000).

Priorities

Considerable strides have been made in reducing "conventional" forms of pollution over the last 30 years by implementation of the Clean Water Act and other federal, state, and local programs. Although further improvements are undoubtedly needed, technology-driven requirements and discharge permitting have been successful in greatly lowering the inputs of many contaminants into U.S. coastal waters. The dumping of sewage sludge and other wastes in the ocean was eliminated. The adverse effects of several manufactured chemicals (DDT, PCBs, and TBT) were uncovered and their use was discontinued or severely restricted.

This is not to say that protection of living marine resources from toxic wastes is no longer an important consideration for ocean policy. Decisions about managing legacy contamination and allowing the use of new chemicals still confront us. Atmospheric deposition and runoff from urban, suburban, and agricultural lands are now predominant pathways for toxic contaminants entering many coastal ecosystems. Abating these sources will require major commitments and innovative approaches.

We now realize that nutrients leaking from our land-based economy--from agriculture, transportation, power generation, and people--are having profound effects on coastal marine ecosystems over larger scales than imagined 30 years ago. The National Research Council (2000a) recommended that reducing nutrient pollution should be a national priority. Our society has just barely begun to accept and address this problem. Significant challenges lie ahead, particularly in ameliorating nitrogen pollution from diffuse sources.

Scales of Pollution Abatement

Meeting environmental quality objectives for the coastal ocean will require pollution abatement efforts at several scales. At the largest scale, managing anthropogenic alterations of the atmosphere and landscape well beyond the traditional "coastal zone" is required. Abating diffuse sources of pollution necessitates national laws and programs that harmonize agriculture, water resource, air quality, transportation, and land conservation policies with coastal environmental quality objectives. For example, the next reauthorization of the Farm Act should contribute to the reduction of nutrient pollution of coastal waters by targeting incentives, subsidies, and assistance while also ensuring economically and socially viable agriculture for the nation.

At the programmatic scale, controlling diffuse sources is clearly the principal challenge for marine pollution abatement. The missing link for the next level of environmental advance is the design and implementation of sustained programs and institutions that address these diffuse sources and provide solutions that are acceptable to American society. Watershed approaches provide a framework but are constrained by weak authorities and the preeminence of traditional governance at state and local levels. The National Research Council (2000a) noted that effective control of multiple sources of nutrients and contaminants on watershed scales would require a mix of voluntary and mandatory approaches and hybrids of these two extremes. Incentives and disincentives included in statutes and management practices can be very important in promoting and shaping voluntary actions involving agriculture and land uses. At the same time, more effective compliance with mandates, such as those already applicable to urban stormwater runoff, should be required.

At the individual scale, many discrete gains may be realized. More demanding treatment standards than those generally applicable can be required where water quality is seriously impaired. Such case-specific requirements generally force technological innovations that are eventually applied more broadly.

Marine Ecosystem Management and Science

Effective ocean resource policies and management regimes must be integrated. Not only must they manage the fish, habitats, and pollution of the coastal ocean more compatibly, but they must also consider and coordinate with land-based activities. Existing regional programs that link activities in the watershed with coastal ecosystem management represent an important start, but much more remains to be accomplished to achieve full integration.

Recognizing inherent uncertainties, policies, and management regimes must also be precautionary and adaptive. As stated in the United Nations Rio Declaration, the precautionary principle requires that: "where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation." Environmental decision-making in the United States has increasingly adopted a more precautionary approach--for example, in the testing of new pesticides and other chemicals before their release in the environment. While application of the precautionary principle may be straightforward in the screening of new chemicals or determining the suitability of dredged material for ocean disposal, it is harder when the ecosystems are already degraded or decisions concern which of many pollutant sources to reduce. Adaptive management involves periodic reevaluation and adjustment of the abatement approach based on careful observation of outcomes.

Integration, precaution, and adaptation in environmental policies and management all rely heavily on science. Scientific research and assessment must not only integrate across scientific disciplines but also address the interactions among the atmosphere, watersheds, and the ocean and relate pollution and other stresses to living marine resources and ecosystem services. The precautionary principle challenges science to quantify risk and determine the level of potential harm required to trigger its application. Adaptive management depends heavily on careful observations and comparison of outcomes to predictions.

Research, monitoring, and assessment relevant to marine pollution need improved strategic focus, organization, and commitment in order to fulfill these roles. The fundamental underpinnings of knowledge of complex environmental processes must be bolstered. The National Research Council (2000b) has identified grand challenges for environmental sciences, several of which are appropriate to marine pollution issues: biogeochemical cycles, biological diversity and ecosystem functioning, climate variability, hydrological forcing, land-use dynamics, and reinventing the use of materials.

Traditional environmental monitoring programs have emphasized relatively static parameters (e.g., contaminant concentrations in sediments or shellfish) rather than the dynamic parameters (e.g., primary production and dissolved oxygen) associated with the effects of nutrient pollution. Observing and understanding the effects of pollution should be an important objective of the sustained, integrated coastal ocean-observing system that is being developed for the nation (Nowlin and Malone, 1999). New sensor technologies, satellite measurements, and vast data storage and computational capabilities provide breakthrough opportunities to observe the environment on the appropriate space and time scales needed to address phenomena, such as eutrophication and harmful algal blooms, which occur over large areas but are highly variable in time.

Observations and research must be brought together in assessments that address key management questions and make useful predictions of probable outcomes. Predictions and observations must continually interact to support adaptive management. This will require new institutional arrangements and sustained commitments that support scientific integration and applied predictions.

VI. Conclusions

Significant accomplishments were realized during the last 30 years in reducing the pollution of U.S. ocean and coastal waters by improving the treatment of waste discharges, ceasing most ocean dumping, and eliminating or restricting the use of certain persistent toxicants. Substantial reductions were realized in the inputs of a number of potentially toxic contaminants and organic wastes. Pollutant inputs from regulated discharges will likely continue to decline in order to attain water-quality standards. However, except for the banned and restricted chemicals, inputs of pollutants from diffuse sources--including land runoff--were largely unabated or actually increased during the same 30 years. Diffuse sources now contribute more than direct discharges for many pollutants.

Although it is difficult to extrapolate effects observed in laboratory experiments, it is clear that toxic contaminants chronically affect marine organisms at least over limited, but widely distributed areas in U.S. coastal waters near heavily populated areas. Toxicants can also affect marine mammals and birds that concentrate organic compounds in fatty tissues, sometimes far from the pollution source.

Persistent and bioaccumulative toxicants remain in the ocean and coastal environment for long periods after their sources have been eliminated or substantially reduced. In many cases little can be done until the substances are gradually degraded or removed from the ecosystem. However, isolated sites have extremely high concentrations of toxicants in bottom sediments, from which they can be reintroduced to the ecosystem. Capping and removal options should be thoroughly evaluated by carefully weighing risks of alternative options.

Overenrichment by plant nutrients, particularly nitrogen, has emerged as the most pervasive pollution risk for living resources and biodiversity in coastal ocean ecosystems. Many of the nations coastal environments exhibit symptoms of overenrichment, including algal blooms (some of which may be toxic), loss of seagrasses and coral reefs, and serious oxygen depletion. Consequences include reduced production of valuable fisheries, threats to biodiversity on regional scales, diminished ecosystem services, and less resilient ecosystems.

Hard-to-control, diffuse sources--often from far inland--dominate nutrient inputs into most overenriched ecosystems. These sources grew dramatically in the last half of the 20 th century as a result of increases in the use of chemical fertilizers, more intensive animal agriculture, and the combustion of fossil fuels that release nitrogen oxides into the air. Only recently has nutrient removal been incorporated in advanced treatment of point sources of wastes. New emission standards to meet air-quality objectives, if fully implemented, could reduce atmospheric deposition of nitrogen by 40 percent. Reduction of agricultural sources of nutrients has been more recalcitrant but it is feasible through improved practices and watershed restoration.

Reversing and controlling diffuse sources of pollution, including nutrients, requires an integrated approach on the scale of an entire drainage basin. The legal and institutional mechanisms available for reducing diffuse-source pollution have thus far been only modestly successful, but watershed management approaches are beginning to have an effect. A combination of voluntary and mandatory actions will be required, assisted by governmental incentives such as tax benefits and subsidies and disincentives. To be most effective, these incentives and disincentives should be targeted geographically. From the broadest policy perspective, effective ocean policy must extend well beyond the ocean and coastal zone to influence agricultural, energy, transportation, water resources, and land-use policies.

Science must play a key role in advancing marine ecosystem management that is integrated, precautionary, and adaptive. Sustained observations of changes related to pollution should be a key part of the nations integrated ocean-observing system. These results should be coupled with strategic research and models to improve predictions needed for adaptive ecosystem management.

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Copyright © 2001 Pew Oceans Commission. All rights reserved.

Pew Oceans Commission
2101 Wilson Boulevard, Suite 550
Arlington, Virginia 22201

# data[].attributes.attachment_link.description
Marine Pollution in the United States Prepared for the Pew Oceans Commission by Donald F. Boesch University of Maryland Center for Environmental Science Richard H. Burroughs University of Rhode Island Joel E. Baker University of Maryland Center for Environmental Science Robert P. Mason University of Maryland Center for Environmental Science Christopher L.

# data[].attributes.headline
Remote Sensing for the Control of Marine Pollution by Jean-Marie Massin

# data[].attributes.subject
Remote Sensing for the Control of Marine Pollution by Jean-Marie Massin

# data[].attributes.body
"After various corrections, mainly
allowing for the solar illumination angle, the cumulative area
covered by the hydrocarbons spread each year in the Mediterranean Sea is crudely estimated to be 175,000 km."

# data[].attributes.headline
Indicators of Marine Pollution in the North Pacific Ocean by Tanya M. Brown and Hideshige Takada

# data[].attributes.subject
Indicators of Marine Pollution in the North Pacific Ocean by Tanya M. Brown and Hideshige Takada

# data[].attributes.body
"This special issue represents the first compilation of research pertaining to marine pollution indicators in the North Pacific Ocean and provides guidance to inform mitigation and monitoring efforts of contaminants in the region."

# data[].attributes.headline
Global research priorities to mitigate plastic pollution impacts on marine wildlife A. C. Vegter, M. Barletta, C. Beck, J. Borrero, H. Burton, M. L. Campbell, M. F. Costa, M. Eriksen, C. Eriksson, A. Estrades, K. V. K. Gilardi, B. D. Hardesty, J.A. Ivar do Sul, J. L. Lavers, B. Lazar, L. Lebreton, W. J. Nichols, C. A. Ribic,P. G. Ryan, Q. A. Schuyler, S. D. A. Smith, H. Takada, K. A. Townsend,C. C. C. Wabnitz, C. Wilcox, L. C. Young, M. Hamann

# data[].attributes.subject
Global research priorities to mitigate plastic pollution impacts on marine wildlife A. C. Vegter, M. Barletta, C. Beck, J. Borrero, H. Burton, M. L. Campbell, M. F. Costa, M. Eriksen, C. Eriksson, A. Estrades, K. V. K. Gilardi, B. D. Hardesty, J.A. Ivar do Sul, J. L. Lavers, B. Lazar, L. Lebreton, W. J. Nichols, C. A. Ribic,P. G. Ryan, Q. A. Schuyler, S. D. A. Smith, H. Takada, K. A. Townsend,C. C. C. Wabnitz, C. Wilcox, L. C. Young, M. Hamann

# data[].attributes.body
"This paper highlights a growing concern related to threats posed to marine wildlife from microplastics and fragmented debris, the need for data at scales relevant to management, and the urgent need to develop interdisciplinary research and management partnerships to limit the release of plastics into the environment and curb the future impacts of plastic pollution"

# data[].attributes.headline
The Effects of Plastic Pollution on Aquatic Wildlife: Current Situations and Future Solutions

# data[].attributes.subject
The Effects of Plastic Pollution on Aquatic Wildlife: Current Situations and Future Solutions

# data[].attributes.body
https://projectdragonfly.miamioh.edu/wp-content/uploads/2019/06/Sigler_Michelle_Water-Air-Soil-Pollut_2014.pdf

This source talks about the different types of animals that are affected by plastic pollution and ways that pollution can be handled. It talks about tracking ocean currents.
"The United Nations has estimated that 5–10 million t of
plastic are circulating in the North Pacific Ocean between California and Japan"
Sigler, M. (2014). The effects of plastic pollution on aquatic wildlife: current situations and future solutions. Water, Air, & Soil Pollution, 225(11), 1-9.

# data[].attributes.body
https://www.researchgate.net/profile/Kyle-Elliott-2/publication/236615111_Environmental_science_Tracking_marine_pollution/links/02e7e529b5c4f9307f000000/Environmental-science-Tracking-marine-pollution.pdf
This article talks about ways that seabirds can help researchers 'Sample' the enviroment. That in turn can help tell how much plastic is in certain areas.
Elliott, J. E., & Elliott, K. H. (2013). Tracking marine pollution. science, 340(6132), 556-558.

# data[].attributes.headline
Linkage between Public Policy, Green Technology and Green Products on Environmental Awareness in the Urban Kuala Lumpur, Malaysia 

# data[].attributes.subject
Linkage between Public Policy, Green Technology and Green Products on Environmental Awareness in the Urban Kuala Lumpur, Malaysia 

# data[].attributes.body
https://www.koreascience.or.kr/article/JAKO201716463831134.pdf
This article talks about how awareness and technology can impact the environment in one place in Malaysia. These strategies could be implemented elsewhere to a certain extent.
Saifullah, M. K., Kari, F. B., & Ali, M. A. (2017). Linkage between public policy, green technology and green products on environmental awareness in the urban Kuala Lumpur, Malaysia. The Journal of Asian Finance, Economics, and Business, 4(2), 45-53.

# data[].attributes.headline
Global threats to human water security and river biodiversity

# data[].attributes.subject
Global threats to human water security and river biodiversity

# data[].attributes.body
https://ap-st01.ext.exlibrisgroup.com/61SCU_INST/upload/1619744389404_fulltext.pdf?Expires=1619744509&Signature=BrfgCDzeXgCEl5YVmi6urZzRnMw9SslEHWB2KkXN2RkhbjmFZoWw95NO5FCAB8quFgOt1njiEGInqFktej~sdCMHg663bCwg0H6n30BNvt7UxalLaMgoR9sO4ji8ITd6x5FrD863BueMf4a1lu6bhi8i5UG5Q4~uOCrfitct6NZUXLgy~P1srIqJ5qus-8yFfyr8u-05LS2ttAN1HedCWsNk5PHL5YxKS5e6OsLPLnG7yYLvpx2Etit9KCSxoxAjTbIOZk~OxWQgkjrVnQWGOlsaceNovNELU--er4yX4OFbCNiShfoylJavDndUGfx~bVqLHrOGoXvYxcpYV-bYOg__&Key-Pair-Id=APKAJ72OZCZ36VGVASIA
This article explains ways that public officials can evaluate water crisis. The authors explain that a balance needs to be struck between human resource use and the environment.
Vörösmarty, C. J., McIntyre, P. B., Gessner, M. O., Dudgeon, D., Prusevich, A., Green, P., ... & Davies, P. M. (2010). Global threats to human water security and river biodiversity. nature, 467(7315), 555-561.

# data[].attributes.headline
Anthropomorphic Green Advertising: How to Enhance Consumers’ Environmental Concern

# data[].attributes.subject
Anthropomorphic Green Advertising: How to Enhance Consumers’ Environmental Concern

# data[].attributes.body
http://dlsu-ber.com/wp-content/uploads/2019/07/7laksmdewi-0719-revised.pdf
This article talks about how making the environment relate more to consumers by means of advertising helps raise environmental concern in people.
Laksmidewi, D., & Soelasih, Y. J. D. B. (2019). Anthropomorphic green advertising: How to enhance consumers’ environmental concern. DLSU Business & Economics Review, 29(1), 72-84.

# data[].attributes.headline
The Debate over Corporate Social Responsibility

# data[].attributes.subject
The Debate over Corporate Social Responsibility

# data[].attributes.body
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.468.7584&rep=rep1&type=pdf#page=388
This article talks about how advertising can help people be aware of the environment and can force public officials into responding to a crisis.
Ongkrutraksa, W. Y. (2007). Green marketing and advertising. The debate over corporate social responsibility, 365-378.

# data[].attributes.headline
A critical review on the sources and instruments of marine microplastics and prospects on the relevant management in China

# data[].attributes.subject
A critical review on the sources and instruments of marine microplastics and prospects on the relevant management in China

# data[].attributes.body
https://journals.sagepub.com/doi/pdf/10.1177/0734242X18793504
This article explains what microplastics are and how they end up in the ocean. Also explains why plastic breaks down slowly.
Wang, J., Zheng, L., & Li, J. (2018). A critical review on the sources and instruments of marine microplastics and prospects on the relevant management in China. Waste Management & Research, 36(10), 898-911.

# data[].attributes.headline
Global research priorities to mitigate plastic pollution impacts on marine wildlife

# data[].attributes.subject
Global research priorities to mitigate plastic pollution impacts on marine wildlife

# data[].attributes.body
https://www.int-res.com/articles/esr_oa/n025p225.pdf
Talks about how plastic kills and injures marine wildlife and why that's important to people. Also talks about the prevalence of plastic
Vegter, A. C., Barletta, M., Beck, C., Borrero, J., Burton, H., Campbell, M. L., ... & Hamann, M. (2014). Global research priorities to mitigate plastic pollution impacts on marine wildlife. Endangered Species Research, 25(3), 225-247.

# data[].attributes.headline
Plastic pollution and potential solutions 

# data[].attributes.subject
Plastic pollution and potential solutions 

# data[].attributes.body
https://journals.sagepub.com/doi/pdf/10.3184/003685018X15294876706211
This article explain many solutions to the plastic problem. They ivlove technology and can help provide me with some solutions.
Rhodes, C. J. (2018). Plastic pollution and potential solutions. Science progress, 101(3), 207-260.

# data[].attributes.headline
The Role of Social Marketing and Sustainable Tourism in Reducing Plastic Pollution (Lynne Eagle, Mark Hamann & David R. Low) 

# data[].attributes.subject
The Role of Social Marketing and Sustainable Tourism in Reducing Plastic Pollution (Lynne Eagle, Mark Hamann & David R. Low) 

# data[].attributes.body
- "As well as the visual impact of litter, plastic bags can impact on population health through the provision of breeding grounds for
disease-carrying mosquitoes. They also can provide a means for invasive species to enter new
habitats, endangering native species (Gregory, 2009)."

- "Plastic is responsible for killing 1 million seabirds and over 100,000 sea mammals each year (Leahy, 2004). Some 267 species, including 86% of all sea turtles, up to 36% of seabirds, and up to 28% of all marine mammals .have been found with ingested plastic (Müller, et al.,
2012). Aside from direct mortality, many animals have been found to consume plastics at non-lethal levels, resulting in dietary dilution and thus potential malnutrition (Schuyler et al., 2012). In non-lethal cases it is possible that there are uptake of plastic toxins which could lead to physiological change or tropic, or food chain, level change (Hirai et al., 2011)."

- "The longevity of the risk to marine life is illustrated by the finding that plastic swallowed by an albatross originated from a plane shot down 60 years earlier and 9,600 km away (Wabnitz & Nichols, 2010)."

- "Successful solutions to the problem of marine pollution require a multi-faceted intervention.
Awareness and educational-based interventions have a role to play in ensuring an understanding of the impact of plastic disposal on marine life and thus encouraging
environmentally appropriate choices..."

# data[].attributes.attachment_link.title
IRRSource The Role of Social Marketing..

# data[].attributes.headline
Channelling passion for the ocean towards plastic pollution (Sabine Pahl, Kayleigh J. Wyles, Richard C. Thompson) 

# data[].attributes.subject
Channelling passion for the ocean towards plastic pollution (Sabine Pahl, Kayleigh J. Wyles, Richard C. Thompson) 

# data[].attributes.body
- "Plastic particles have been found
in commercially important seafood, in rivers and soils, and in salt for human consumption, although effects on human health are as yet unknown..."

- "While media images are emotive and such initiatives have important local impact, they may not be sufficiently connected to the real underlying cause: the broader societal systems and habits that make plastic ubiquitous."

- "... end-of-pipe solutions such clean-ups have, up to now, received
greater attention than have systemic approaches to stop the problem at its source. This is akin to fixing an overflowing bath by mopping up the water spilling onto the floor rather than turning off the tap."

- "The combination of practical benefit, wide availability and lack of immediately visible harm when using plastics in daily life makes it harder to establish social norms of less plastic or to motivate people to dispose of plastics properly. It may
also conjure up feelings of helplessness and lack of control, against a society that does not appear to care about plastic."

- "Could we motivate action on plastic pollution by using powerful images on everyday products? Changes to cigarette packaging have seen the introduction of
graphic images showing health impacts to reduce smoking. Applying this approach to plastic products could be one method
of linking people’s passion for the ocean to the use of plastics in daily life, potentially resulting in more careful consumption and disposal behaviours."

# data[].attributes.attachment_link.title
IRRSource Channelling passion for the ocean towards plastic pollution

# data[].attributes.headline
Sampling the Sea: Using Social Media for an Online Ocean Stability Curriculum (Ronald E. Rice, Julie A. Robinson, Bruce Caron)

# data[].attributes.subject
Sampling the Sea: Using Social Media for an Online Ocean Stability Curriculum (Ronald E. Rice, Julie A. Robinson, Bruce Caron)

# data[].attributes.body
- "Ocean literary curriculum units, lessons, and activities centered in issue-based learning can be used to  increase opportunities to engage students in active and authentic ocean science inquiry (Wilmes and Howarth 2009). These opportunities can now be enhanced through the use of online social media in support of participatory learning in, across, and outside of classrooms."

- "... the use of social media and social networking in the curriculum should allow students to bring their outside-of-school media sharing expertise and interests into the classroom (Rheingold 2008) and enhance opportunities for peer-to-peer, or cooperative learning."

- "... social media can offer students possibilities to integrate new important skills: distributed cognition, collective intelligence, transmedia navigation, and even play, as several examples."

# data[].attributes.attachment_link.title
IRRSource Sampling the Sea Using Social Media..

# data[].attributes.headline
Did the Blue Planet set the Agenda for Plastic Pollution? An Explorative Study on the Influence of a Documentary on the Public, Media and Political Agendas (Jennifer Males, Peter Van Aelst)

# data[].attributes.subject
Did the Blue Planet set the Agenda for Plastic Pollution? An Explorative Study on the Influence of a Documentary on the Public, Media and Political Agendas (Jennifer Males, Peter Van Aelst)

# data[].attributes.body
- "The results also seem to imply that The Blue Planet generated
this interest in plastic pollution which was, for both the media and
political agendas, long-lasting. These results have implications for
understanding the importance of documentaries as a viable source of
putting environmental issues on the public, media and political agendas."

- "There is growing consensus that
these types of films are no longer intended solely to entertain or inform the public, but are in
fact, a strong potential advocate for relevant social issues (Nisbet & Aufderheide, 2011, p. 450)."

- "The results imply that the documentary was extremely influential in generating interest in plastic pollution by the public, media and politicians, suggesting that documentaries can be used as a powerful tool for advocating issue salience."

- "For example, stories are often sensationalized or dramatized to generate more interest in an issue. Second, if the media gives more attention to an issue, the public will more likely consider it to be important. Research into this theory indicates a significant relationship between the level of coverage by the media of certain topics and the degree of salience of these issues among the general public (Ader, 1995; Dotson et al., 2012)."

- "Although little is known about the extent to which documentaries can influence policy making (Vasi et al., 2015, p. 935), there is some proof
that they can initiate political debates over social issues (Nisbet & Aufderheide, 2011, p. 450)."

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IRRSource Did the Blue Planet set the Agenda for Plastic Pollution

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Using social media to strengthen public awareness of wildlife conservation (Yinglin Wu, Ling Xie, Shiang-Lin Huang,  Ping Li, Zengwei Yuan, Wenhua Liu) 

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Using social media to strengthen public awareness of wildlife conservation (Yinglin Wu, Ling Xie, Shiang-Lin Huang,  Ping Li, Zengwei Yuan, Wenhua Liu) 

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- "Therefore, strengthening public awareness plays an increasingly important role in evoking stewardship of environmental
protection and biological conservation issues (Jefferson et al., 2015; Steel et al., 2005)."

- "...studies have shown that even conservation science information
extracted from professional conferences can be delivered to more audience via social media forums such as Twitter (Bombaci et al., 2015; Shiffman, 2012)"

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IRRSource Using social media to strengthen public awareness of wildlife conservation

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Enhancing public awareness and promoting co-responsibility for marine litter in Europe: the challenge of MARLISCO (Joana M. Veiga,  Thomais Vlachogianni, Sabine Pahl, Richard Thompson,  Kathrin Kopke,  Thomas K. Doyle, Bonny L. Hartley, Thomas Maes, Demetra L. Orthodoxou, Xenia I. Loizidou, Iro Alampei)

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Enhancing public awareness and promoting co-responsibility for marine litter in Europe: the challenge of MARLISCO (Joana M. Veiga,  Thomais Vlachogianni, Sabine Pahl, Richard Thompson,  Kathrin Kopke,  Thomas K. Doyle, Bonny L. Hartley, Thomas Maes, Demetra L. Orthodoxou, Xenia I. Loizidou, Iro Alampei)

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- "At present, problems associated with marine litter are exacerbated by a combination of: lack of awareness within society on the extent of the problem; lack of awareness of potential solutions; and lack of communication and
articulation mechanisms between the different stakeholders."

- "As in other complex environmental issues, the problem is not always related to a lack of knowledge but rather to the context for using this knowledge and incentives to actually turn it into action (Naustdalslid, 2011)."

- "A range of initiatives have been implemented throughout Europe involving the general public in taking action against marine litter or to be actively engaged in waste prevention and management."

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IRRSource Enhancing public awareness and promoting co-responsibility for marine litter in Europe the challenge of MARLISCO

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Public awareness, concerns, and priorities about anthropogenic impacts on marine environments (Stefan Gelcich, Paul Buckley, John K. Pinnegar, Jason Chilvers, Irene Lorenzoni, Geraldine Terry, Matias Guerrero, Juan Carlos Castilla, Abel Valdebenito, Carlos M. Duarte)

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Public awareness, concerns, and priorities about anthropogenic impacts on marine environments (Stefan Gelcich, Paul Buckley, John K. Pinnegar, Jason Chilvers, Irene Lorenzoni, Geraldine Terry, Matias Guerrero, Juan Carlos Castilla, Abel Valdebenito, Carlos M. Duarte)

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- "Although significant relationships between informedness and
concern are prevalent in our results, personal experience and
informedness alone do not necessarily fully account for concern, and personal risk, interest, and moral values—not assessed here—can also play important roles."

- "Public views, in conjunction with expert opinion, can help focus
international, national, and local initiatives in prioritizing the most
important or most manageable marine impacts. Indeed, there is
considerable consensus between the citizens’ responses to the survey and the outcome of a systematic assessment of ocean threats..."

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IRRSource Public awareness, concerns, and priorities about anthropogenic impacts on marine environments

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Mixing oil and water:Tracking the Sources and Impacts of Oil Pollution in the Marine Environment. (John W. Farrington and Judith E. McDowell)

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Mixing oil and water:Tracking the Sources and Impacts of Oil Pollution in the Marine Environment. (John W. Farrington and Judith E. McDowell)

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" Long-term effects of oil exposure can alter the physiology and ecology of populations of marine organisms, especially those found in sensitive habitats."

This articles talks about how oil pollution affects the whole ocean. It talks about how it gets in the ocean, what it does to animals and their habitats, what it does to the ocean water, and how to get rid of it.

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Drop by drop--that is how most oil enters the oceans. Catastrophic spills make the headlines, but it is the chronic dribble, dribble, dribble of seemingly small inputs that supplies most of the oil pollution in the world's oceans.

In recent decades scientists have made substantial progress in understanding how oil enters the oceans, what happens to it, and how it affects marine organisms and ecosystems. This knowledge has led to regulations, practices, and decisions that have helped us reduce sources of pollution, prevent and respond to spills, clean up contaminated environments, wisely dredge harbors, and locate new petroleum handling facilities.

But tracking the sources, fates, and effects of oil in the marine environment remains a challenge for a number of reasons. For starters, oil is a complicated mixture of hundreds, sometimes thousands, of chemicals. Every source of oil, and even the same general types of oil (crude oils or fuel oils, for example) can have distinctive compositions depending on which oil field or well they came out of and how they were refined.

This varying, complex mixture of chemicals gets spilled or seeps into an already complex chemical chowder of seawater, mud, and marine organisms in the ocean. There, the oil is stirred by currents, tides, and waves, altered by other physical processes, and changed further by chemical reactions and interactions with organisms in the sea.

In the midst of this dynamic situation, scientists seek to pinpoint the impacts of oil on myriad individual species, as well as on entire ecosystems. Here the challenge comes full circle, because we now know that the impact of oil can vary greatly, depending on its distinctive chemical composition. But let's start at the beginning.

How does oil get into the ocean?

Scientists have known since the 1970s that accidents account for only a small percentage of the oil entering our waters. In fact, accidental spills of all types--from ships, shore facilities, pipelines, and offshore platforms--contributed just 9.8 percent of the oil entering the marine environment on an annual, worldwide basis between 1990 and 1999 (but just 3 to 4 percent in U.S. waters).

That doesn't mean we should dismiss the importance of spills. Accidents such as the 1989 Valdez incident off Alaska or the 2002 Prestige spill off Spain can have devastating effects on marine life and on people's ability to use the ocean. The impact of a spill depends on the type of oil, the amount spilled, the ocean and weather conditions, and the dynamics of the area or ecosystem where it takes place.

Progress in prevention--through more stringent laws, rules, and guidelines, and increased vigilance by industry and regulators--has reduced accidental spills, at least in developed countries. For instance, studies of tanker spills have prompted regulations for the steady, ongoing replacement of single-hulled tankers in the world fleet with double-hulled tankers.

But spills are just one small way, albeit dramatic, for oil to mix with our waters. So where is the rest of it coming from?

* Seeps: Between one-third and one-half of the oil in the ocean comes from naturally occurring seeps. These are seafloor springs where oil and natural gas leak and rise buoyantly from oil-laden, sub-seafloor sediments that have been lifted close to Earth's surface by natural processes.

If oil is natural to the oceans and if it is the biggest source of input, what is the fuss about oil as a pollutant? The answer lies in the locations and rates of oil inputs. Oil seeps are generally old, sometimes ancient, so the marine plants and animals in these ecosystems have had hundreds to thousands of years to adjust and acclimate to exposure to petroleum chemicals. On the other hand, the production, transportation, and consumption of oil by humans often results in the addition of oil to environments and ecosystems that have not experienced significant direct inputs and have not become acclimated.

* Extraction: Accidental and normal operation of oil drilling and production platforms puts some oil into the sea, including oil mixed into the briny waters that escape from the oil reservoirs. But this spillage and waste, and the atmospheric releases from platform equipment, is one of the smallest sources of oil in the sea.

* Transportation: In the 1960s and 1970s, scientists studied tar balls collected along major tanker routes and the beaches downstream. They revealed that large amounts of oil were entering the marine environment as a result of ballast water (bilge) discharges and other aspects of "normal" tanker operations. As a result of that research, international conventions and national laws and regulations have led oil shippers to minimize their discharges, particularly in harbors. Today, in spite of increasing numbers of tankers plying the seas, the amount of oil spewed has stabilized or decreased in many places.

* Consumption: The everyday use of oil in cars, trucks, industrial and manufacturing plants, and other machinery of the modern economy is the most egregious and insidious source of oil pollution. The drippings and emissions from millions of machines accumulate on land and eventually run into our waterways.

From the 1950s through the 1970s, one of the most common sources was the indiscriminate disposal of used automobile crankcase oil down sewer systems. Since that time, scientific findings have prompted regulations and public awareness campaigns that promote the recycling and proper disposal of used oil.

But we still have a problem. Peer underneath your parked car and observe the drip of oil. This happens day and night for millions of automobiles, trucks, and buses, creating a chronic, significant source of oil to the sea. Rainstorms wash these drippings into streams or storm sewers that discharge into harbors and rivers. It is terribly hard to measure these types of inputs.

Fossil fuel hydrocarbons from engine exhaust also accumulate in the atmosphere. Sometimes the soot is deposited into our waters; otherwise it is washed out of the atmosphere and into the oceans by rain or snow.

On a smaller scale, new research has shown that outboard engines of small boats and pleasure craft are a significant source of oil pollution--up to 2.2 percent of all inputs in U.S. waters (worldwide data are not available). Engine manufacturers are responding with new models of engines that release much less oil and gasoline, but it may take some time for these changes to propagate through the boating community.

What happens to oil in the ocean?

Oil chemicals entering the ocean have many fates. Volatile chemicals are lost by evaporation to the atmosphere. Other chemicals are broken up by photochemical reactions (catalyzed by sunlight). Bacteria can degrade certain oil components.

The combination of biological, physical, and chemical processes is usually referred to as weathering. These weathering reactions have different rates depending on the chemical structure of the oil, habitat conditions (such as water temperature or oxygen and nutrient supply), and mixing of the water by wind, waves, and currents. In some spills, oil does not last much beyond weeks to months.

But when oil pours into shallow waters with muddy sediments--such as marshes or lagoons--and conditions allow the oil to become mixed into the mud, it will generally persist for a long time. This is a result of the fundamental chemistry of oil compounds. Since they don't dissolve in water, oil compounds tend to adhere to particles in the water or get incorporated into biological debris, such as fecal matter or dead organisms. These oiled particles and debris settle from the water column and become part of the sediments on the bottom.

Once mired in the sediment, some oil chemicals can persist for years or decades, depending on the environment. In areas swept by high-energy currents, the material may be dispersed. In areas where sediments accumulate (such as ship channels through urban harbors), the contaminated sediments become an environmental concern--both when simply lying on the bottom and when channels are dredged and the mud must be disposed.

For some types of oil inputs and some ecosystems, we now have enough information to model and simulate the fate of oil in the water. This scientific knowledge helps policymakers make better decisions on how to dredge harbors, control pollution sources, clean up contaminated areas, and locate petroleum facilities.

How does oil affect marine life?

From experiments and field measurements, we know that certain types and concentrations of petroleum chemicals can harm marine life. Long-term effects of oil exposure can alter the physiology and ecology of populations of marine organisms, especially those found in sensitive habitats.

Biological and physical processes can reduce the concentration of oil chemicals in an ecosystem, especially if the source of pollution is cut off. As concentrations decline and chemical compositions change, plant and animal communities usually rebound. But the recovery can range from months to decades depending on the chemistry, the conditions, and the organisms and ecosystems affected.

One of the significant advances in the 1970s and 1980s was the development of guides to the sensitivity of various types of coastal ecosystems to oil pollution. Maps of sensitive ecosystems are now used during responses to accidental oil spills, improving the ability of resource managers and engineers to assess where containment booms and other prevention and cleanup measures should be deployed.

There have been few studies, however, on the cumulative effect of chronic inputs of oil to the marine environment, including the many sources associated with oil consumption on land. Assessing these impacts is complicated because oil runoff is often accompanied by other polluting chemicals, making it difficult to tease out which ones have which deleterious effects. Limited experiments have taught us that the interactive effects among chemicals can either increase or decrease each chemical's long-term effects, depending on the organisms and chemicals.

Much of our knowledge about the effects of oil is still limited. It has focused on biochemical and physiological effects on a few individual organisms and on the degradation of a few particular habitats. But we need a better understanding of the large-scale effects of oil on entire communities and populations, rather than individual organisms. The complexity of how species interact within ecosystems--such as how damage to one species can affect the other species that feed on it--leads to contentious debate whenever regulators start to weigh long-term impacts on marine life.

Fuel for further research

A high priority for the future should be better monitoring and research so we can better quantify how much oil is really entering our waters, how much of it is coming from each source, and what the effects may be.

We also need to expand research on oil pollution in deeper waters. Most concerns and research have traditionally focused on coastal waters. Yet new concerns arise as oil production moves offshore. We can only speculate on the impact of oil exploration and production in deeper waters until we have more detailed knowledge of the biological organisms in these habitats and the biogeochemical processes that govern their lives.

Developed countries and emerging countries consume more oil every year, and that consumption leads to more and more inputs of oil to the oceans. We have learned from our colleagues in developing countries that increased use of fossil fuels has not been accompanied by the sort of stringent regulations developed countries adopted after years of harsh lessons. Further research and education can help those countries minimize the adverse impacts of oil inputs on their oceanic ecosystems.

--A recent study by the U.S. National Academy of Sciences, entitled Oil in the Sea III: Inputs, Fates and Effects, provided the foundation for this article.

John Farrington came to WHOI in 1971 as a postdoctoral investigator in the Chemistry Department following completion of bachelor's and master's degrees at Southeastern Massachusetts University and a doctorate at the University of Rhode Island. His research interests include marine organic geochemistry, biogeochemistry of organic chemicals of environmental concern, and the interaction between science and policy. He has served on scientific advisory panels for the National Academy of Sciences, the National Science Foundation, the Office of Naval Research, and the Commonwealth of Massachusetts.

Judith McDowell earned her bachelor's degree in biology from Stonehill College and her master's and doctorate degrees in zoology from the University of New Hampshire. Judy's research focuses on the ecology of marine animals and the effects of chemical contaminants on the marine environment. She has served on the Committee on Oil in the Sea for the National Research Council. She is director of the Woods Hole Sea Grant Program.

John W. Farrington, Senior Scientist Vice President and Dean of Academic Programs and Judith E. McDowell, Senior Scientist Biology Department Associate Dean of Academic Programs Woods Hole Oceanographic Institution

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Mixing oil and water: tracking the sources and impacts of oil pollution in the marine environment

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Drop by drop--that is how most oil enters the oceans. Catastrophic spills make the headlines, but it is the chronic dribble, dribble, dribble of seemingly small inputs that supplies most of the oil pollution in the world's oceans.

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Ocean Pollution (National Oceanic and Atmospheric Administrations.) 

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Ocean Pollution (National Oceanic and Atmospheric Administrations.) 

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"Our ocean and waterways are polluted with a wide variety of marine debris, ranging from tiny microplastics, smaller than 5 mm, to derelict fishing gear and abandoned vessels."

This article talks about the different kind of pollution in the ocean and the great lakes. This source also talks about how it affects the animals and their food because some marine animals are eating plastic. There is also a lot of micro-plastic that is affecting the ocean.

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Marine Pollution explained. (Jenny Howard)

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Marine Pollution explained. (Jenny Howard)

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"Chemical pollution is the introduction of harmful contaminants. Common man-made pollutants that reach the ocean include pesticides, herbicides, fertilizers, detergents, oil, industrial chemicals, and sewage."

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THE OCEANS ARE so vast and deep that until fairly recently, it was widely assumed that no matter how much trash and chemicals humans dumped into them, the effects would be negligible.

Today, we need look no further than the New Jersey-size dead zone that forms each summer in the Gulf of Mexico, or the thousand-mile-wide belt of plastic trash in the northern Pacific Ocean to see that this early "policy" placed a once flourishing ocean ecosystem on the brink of collapse.

Many "flavors" of marine pollution

Ocean water covers more than 70 percent of the Earth, and only in recent decades have we begun to understand how humans impact this watery habitat. Marine pollution, as distinct from overall water pollution, focuses on human-created products that enter the ocean.

Before 1972, humans around the word spewed trash, sewage sludge, and chemical, industrial, and radioactive wastes into the ocean with impunity. Millions of tons of heavy metals and chemical contaminants, along with thousands of containers of radioactive waste, were purposely thrown into the ocean.

The London Convention, ratified in 1975 by the United States, was the first international agreement to spell out better protection for the marine environment. The agreement implemented regulatory programs and prohibited the disposal of hazardous materials at sea. An updated agreement, the London Protocol, went into effect in 2006, more specifically banning all wastes and materials except for a short list of items, like leftover materials from dredging.

Many of these pollutants sink to the ocean's depths or float far distances from their original source, where they are consumed by small marine organisms and introduced into the global food chain. Marine pollution encompasses many types of pollution that disrupt the marine ecosystem, including chemical, light, noise, and plastic pollution.

Chemical pollution

Chemical pollution is the introduction of harmful contaminants. Common man-made pollutants that reach the ocean include pesticides, herbicides, fertilizers, detergents, oil, industrial chemicals, and sewage.

Many ocean pollutants are released into the environment far upstream from coastlines. Nutrient-packed fertilizers applied to farmland, for example, often end up in local streams and are eventually deposited into estuaries and bays. These excess nutrients trigger massive blooms of algae that rob the water of oxygen, leaving dead zones where few marine organisms can live. Some chemical pollutants climb high into the food webs-like DDT, the insecticide that placed the bald eagle on the United States Fish and Wildlife's endangered species list.

Scientists are starting to better understand how specific pollutants, leached into the ocean from other materials, affect marine wildlife. PFAS, a chemical incorporated into many household products, accumulates in human and marine mammal blood. Even pharmaceuticals ingested by humans, but not fully processed by our bodies, end up in aquatic food webs.

Light pollution

Since the invention of the lightbulb, light has spread across the globe, reaching almost every ecosystem. Often thought of as a terrestrial problem, scientists are starting to understand how artificial light at night affects many marine organisms.

Light pollution penetrates under the water, creating a vastly different world for fish living in shallow reefs near urban environments. Light disrupts the normal cues associated with circadian rhythms, to which species have evolved timing of migration, reproducing, and feeding. Artificial light at night can make it easier for predators to find smaller fish prey and can affect breeding in reef fish.

Noise pollution

Pollution is not always visible. In large bodies of water, sound waves can carry undiminished for miles. The increased presence of loud or persistent sounds from ships, sonar devices, and oil rigs disrupts natural noises in the marine environment.

For many marine mammals, like whales and dolphins, low visibility and large distances make non-visual underwater communication critical. Toothed whales use echolocation-emitting sounds that reflect off surfaces-to help them "see" in the ocean. Unnatural noises interrupt communication, disrupting migration, communication, hunting, and reproduction patterns for many marine animals.

Plastic pollution

Plastic pollution seeps into the ocean through run-off and even purposeful dumping. The amount of plastic in the Atlantic Ocean has tripled since the 1960s. The garbage patch floating in the Pacific Ocean, almost 620,000 square miles- twice the size of Texas -is a powerful image of our plastic problem.

A huge culprit is single-use plastics, used once before tossed into the trash or directly into the ocean. These single-use items are accidentally consumed by many marine mammals. Plastic bags resemble jellyfish, a common food for sea turtles, while some seabirds eat plastic because it releases a chemical that makes it smell like its natural food. Discarded fishing nets drift for years, ensnaring fish and mammals.

Bits of plastic swirl throughout the water column, even sinking to the deepest depths of the ocean. Scientists found plastic fibers in corals in the Atlantic Ocean-and more concerning, they found that the corals readily ate plastic over food. Dying marine mammals, washing up on shore, also contain plastic inside their stomachs.

Is there a "fix" to marine pollution?

Many national laws, as well as international agreements, now forbid dumping of harmful materials into the ocean, although enforcing these regulations remains a challenge.

Many pollutants still persist in the environment, difficult to fully remove. Chemical pollutants often cannot be broken down for long periods of time, or they increase in concentration as they move up the food web. Because plastic is thought to take hundreds of years to break down, it poses a threat to the marine environment for centuries.

Isolated efforts to restore estuaries and bays have met with some success, but pollution gets trapped in marine sediment and makes complete clean-ups nearly impossible.

Moving forward, encouraging recycling and reuse can minimize plastic pollution. Dampening unnecessary lights at night can limit light pollution. And encouraging responsible chemical-use through consumer and political actions can protect the environment for the future.

National Geographic is committed to reducing plastics pollution. Learn more about our non-profit activities at natgeo.org/plastics. Learn what you can do to reduce your own single-use plastics, and take your pledge.

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THE OCEANS ARE so vast and deep that until fairly recently, it was widely assumed that no matter how much trash and chemicals humans dumped into them, the effects would be negligible.

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Oil Spills (National Oceanic and atmospheric administration) 

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Oil Spills (National Oceanic and atmospheric administration) 

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"Where the oil is spilled, what kinds of plants, animals, and habitats are found there, and the amount and type of oil, among other things, can influence how much harm an oil spill causes."

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Garbage Patches (NOAA Marine Debris Program)

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Garbage Patches (NOAA Marine Debris Program)

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"Marine life can be caught and injured, or potentially killed in certain types of debris."
"We know that this can be harmful to the health of fish, seabirds, and other marine animals."

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What and Where Are Garbage Patches?

Garbage patches are large areas of the ocean where litter, fishing gear, and other debris - known as marine debris - collects. They are formed by rotating ocean currents called "gyres." You can think of them as big whirlpools that pull objects in. The gyres pull debris into one location, often the gyre's center, forming "patches."

There are five gyres in the ocean. One in the Indian Ocean, two in the Atlantic Ocean, and two in the Pacific Ocean. Garbage patches of varying sizes are located in each gyre.

The most famous of these patches is often called the "Great Pacific Garbage Patch." It is located in the North Pacific Gyre (between Hawaii and California). "Patch" is a misleading nickname, causing many to believe that these are islands of trash. Instead, the debris is spread across the surface of the water and from the surface all the way to the ocean floor. The debris ranges in size, from large abandoned fishing nets to tiny microplastics, which are plastic pieces smaller than 5mm in size. This makes it possible to sail through some areas of the Great Pacific Garbage Patch and see very little to no debris.

The Great Pacific Garbage Patch

The Great Pacific Garbage Patch is in the Pacific Ocean between Hawaii and California. It is the most well known patch. While some areas of the patch have more trash than others, much of the debris is made of microplastics (by count). Because microplastics are smaller than a pencil eraser, they are not immediately noticeable to the naked eye. It's more like pepper flakes swirling in a soup than something you can skim off the surface. You may come across larger items, like plastic bottles and nets, but it's possible to sail through some areas of a garbage patch and not see any debris at all. Garbage patches are huge! It's difficult to determine an exact size as the trash is constantly moving with ocean currents and winds.

The Impact of Garbage Patches on the Environment

Garbage patches, especially the Great Pacific Garbage Patch, are far out in the middle of the ocean where people hardly ever go. Because they are so remote, it can be hard to study them. Scientists rarely get to see the impacts of garbage patches on animals first hand. So far, we know that marine debris found in garbage patches can impact wildlife in a number of ways:

Entanglement and ghost fishing: Marine life can be caught and injured, or potentially killed in certain types of debris. Lost fishing nets are especially dangerous. In fact they are often called "ghost" nets because they continue to fish even though they are no longer under the control of a fisher. Ghost nets can trap or wrap around animals, entangling them. Plastic debris with loops can also get hooked on wildlife - think packing straps, six-pack rings, handles of plastic bags, etc.

Ingestion: Animals may mistakenly eat plastic and other debris. We know that this can be harmful to the health of fish, seabirds, and other marine animals. These items can take up room in their stomachs, making the animals feel full and stopping them from eating real food.

Non-native species: Marine debris can transport species from one place to another. Algae, barnacles, crabs, or other species can attach themselves to debris and be transported across the ocean. If the species is invasive, and can settle and establish in a new environment, it can outcompete or overcrowd native species, disrupting the ecosystem.

Garbage Patches and Human Health

We don't know whether, or how, garbage patches are impacting human health. Generally speaking, we know that humans may be exposed to microplastics from a number of sources, such as seafood, sea salt, tap water, beer, and even honey. However, we do not know how or if humans are impacted by this. Plastic microfibers can also be transported in the air and found in household dust (e.g., from furniture, carpet, clothing etc.), so exposure from seafood and other ocean sources may be small in comparison. The research community is actively exploring this issue.

Marine debris in garbage patches can have other impacts. For example, it may also cause damage to vessels and be a navigation hazard. Marine debris can be difficult to see in the ocean if it's floating below the water surface. A boat moving through the water can hit the debris, possibly resulting in costly vessel damage. Nets can become entangled in propellers and clog intakes.

What Happens If Nothing Changes?

The answer is that we do not know. The locations and sizes of these garbage patches are not likely to change very much any time soon. However, the amount of debris may continue to grow as more and more debris enters our ocean each year. This growth will likely worsen current impacts on the environment, navigation, vessel safety, and the economy.

How Do We Get Rid of Garbage Patches?

It may not be possible to entirely get rid of garbage patches. Some of the material will take a very long time to break down in the environment, while other materials, like plastics, may never fully go away. Large debris, like fishing nets, can be removed by people, but debris in the garbage patches is also mostly made up (by count) of plastic pieces smaller than 5mm in size. The debris is also continuously mixed by wind and wave action and is spread from the surface all the way to the ocean floor. Since these microplastics are so small in size, constantly being mixed, and spread out, it would be very difficult to remove them. Finding a cost effective technological solution which can take on these challenges is an extremely daunting task. Unfortunately, we will be dealing with this problem for the foreseeable future.

Here at the NOAA Marine Debris Program, we focus on marine debris prevention and removal from shorelines and coastal areas where debris is easier to pick up. Prevention is key to solving the marine debris problem over time. If you think about an overflowing sink, the first step before cleaning up the water is to turn the tap off. That is exactly how prevention works. By acting to prevent marine debris, we can stop this problem from growing.

To prevent marine debris, we need to understand where it is coming from. It's hard to identify specific sources, but we know that marine debris can enter our waterways and ocean in a variety of ways. Ineffective or improper waste management, dumping or littering, and stormwater runoff all lead to marine debris. If we want to "turn off the tap," everyone, including government, businesses, and people like you, will have to make some meaningful changes. We are the problem, and so we must also be the solution

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Learn more about what garbage patches are, their impacts on the ocean, and what we can do about them.

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Ocean Pollution:The Dirty Facts (Melissa Denchak)

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Ocean Pollution:The Dirty Facts (Melissa Denchak)

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"It’s estimated that by the end of this century, if we keep pace with our current emissions practices, the surface waters of the ocean could be nearly 150 percent more acidic than they are now."

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Covering more than 70 percent of our planet, oceans are among the earth's most valuable natural resources. They govern the weather, clean the air, help feed the world, and provide a living for millions. They also are home to most of the life on earth, from microscopic algae to the blue whale, the largest animal on the planet. Yet we're bombarding them with pollution. By their very nature-with all streams flowing to rivers, and all rivers leading to the sea-the oceans are the end point for so much of the pollution we produce on land, however far from the coasts we may be. And from dangerous carbon emissions and choking plastic to leaking oil and constant noise, the types of ocean pollution that humans generate are vast. As a result, collectively, our impact on the seas is degrading their health at an alarming rate. Here are some ocean pollution facts that everyone on our blue planet ought to know.

Ocean acidification

When we burn fossil fuels, we don't pollute just the air but the oceans too. Indeed, today's seas absorb as much as a quarter of all man-made carbon emissions, which changes the pH of surface waters and leads to acidification (pH is a measure of how acidic or basic water is). This problem is rapidly worsening-oceans are now acidifying faster than they have in some 300 million years. In absorbing so much of the carbon emissions from the atmosphere, the pH level of the ocean surface has increased an estimated 30 percent since the start of the industrial revolution 200 years ago. If greenhouse gas emissions continue to increase, the surface waters of the ocean could be nearly 150 percent more acidic by the end of the century.

So what happens when the ocean's chemistry is knocked out of whack? Marine ecosystems-and the coastal economies that depend on them-go out of whack too. Take reefs and shellfish, for starters. To build their shells and skeletons, creatures like mussels, clams, coral, and oysters require calcium carbonate (the same compound found in chalk and limestone). But the ocean's carbonate levels go down when acidity levels rise, threatening the survival of these animals. Bivalves are at the bottom of the food chain, so these effects ripple up to many fish, seabirds, and marine mammals. More-acidic waters also contribute to the bleaching of coral reefs and make it harder for some types of fish to sense predators and for others to hunt prey.

Meanwhile, ocean acidification threatens us land dwellers too. The billion-dollar American shellfish industry is the economic backbone of myriad coastal communities, from Louisiana to Maryland to Maine. In the Pacific Northwest, the shellfish that are vulnerable to ocean acidification make up more than 60 percent of the fishery revenue. In total, the U.S. shellfish industry could lose more than $400 million annually by 2100 due to impacts of ocean acidification.

Trash in the ocean

The majority of the garbage that enters the ocean each year is plastic-and here to stay. That's because unlike other trash, the single-use plastic bags, water bottles, drinking straws, and yogurt containers, totalling some eight million metric tons of the plastic waste we toss (instead of recycling), won't biodegrade. Instead, they can persist in the environment for a millennium, polluting our beaches, entangling marine life, and getting ingested by fish, whales, turtles, and seabirds.

The most infamous example of marine debris is the Great Pacific Garbage Patch. But these patches (which are more like " soups") represent only a fraction of the trash in our oceans. In fact, plastic debris has been found at the bottom of the deepest ocean trench.

Where does all this debris originate? While some is dumped directly into the seas, 80 percent of marine litter makes its way there gradually from land-based sources―including those far inland―via storm drains, sewers, and other routes, according to the National Oceanic and Atmospheric Administration (NOAA). Oil from boats, airplanes, cars, trucks, and even lawn mowers is contributing to water pollution circulating in ocean waters. (An excellent reason for why we should all reduce plastic pollution, no matter where we live.) Chemical discharges from factories, raw sewage overflow from water treatment systems, and stormwater and agricultural runoff add other forms of marine-poisoning pollutants to the toxic brew, contributing to algal blooms and aquatic dead zones.

Ocean noise

The ocean is far from being a " silent world." Sound waves travel farther and faster in the sea's dark depths than they do in the air, and many marine mammals like whales and dolphins, in addition to fish and other sea creatures, rely on communication by sound to find food, mate, and navigate. But an increasing barrage of human-generated ocean noise pollution is altering the underwater acoustic landscape, harming-and even killing-marine species worldwide.

Consider the incessant din of the roughly 60,000 commercial tanker and container ships that ply the seas at any given time. The underwater racket that results creates a kind of "smog" that reaches nearly every corner of the ocean and shrinks the sensory range of marine wildlife. High-intensity sonar used by the U.S. Navy for testing and training causes some of the same effects-and has been linked to mass whale strandings.

Meanwhile, in the hunt for offshore oil and gas, ships equipped with high-powered airguns fire compressed air into the water every 10 to 12 seconds for weeks to months on end. Traveling as far as 2,500 miles, these deafening seismic blasts disrupt foraging, mating, and other vital behaviors of endangered whales (and may ultimately push some, such as the North Atlantic right whale, to extinction). The blasts lead some commercial fish species to abandon their habitat-a direct hit on coastal economies dependent on catch rates; they also injure and kill marine invertebrates, including scallops, crabs, and squid.

Offshore drilling

In addition to noise pollution, the oil and gas industry's routine operations emit toxic by-products, release high levels of greenhouse gases, and lead to thousands of spills in U.S. waters annually. That oil can linger for decades and do irreversible damage to delicate marine ecosystems. Take the 1989 Exxon Valdez tanker spill in Alaska's Prince William Sound, from which oil still remains, or the 2010 BP Deepwater Horizon offshore drilling disaster, which spread millions of gallons of oil throughout the Gulf of Mexico, imposing a heavy toll on coastal communities. But smaller spills also pollute the ocean (and the air) with long-lasting impacts. Even the most advanced cleanup efforts remove only a fraction of the oil, and sometimes they use hazardous technologies. Chemical dispersants used in the largest spill response efforts-1.8 million gallons were released into the Gulf after the BP disaster-are dangerous pollutants themselves.

NRDC works to defend our oceans

From the earliest days of NRDC's founding, we've advocated-and litigated-to protect the world's oceans. As political tides changed in Congress and the White House, NRDC has been steadfast in our defense of policies that protect marine species, as well as coastal communities and their ocean-based economies. In addition to advocating for climate policies that will ensure the health of marine ecosystems, NRDC has played a key role in halting offshore drilling and seismic blasting in the Arctic and Atlantic oceans, in the creation of the Atlantic's first marine national monument, and in the push for more sustainable, ethical seafood. Today, we're part of a growing coalition calling for governments to fully and highly protect at least 30 percent of our oceans by 2030 (part of what's known as " 30x30 ") to help safeguard the marine ecosystems and fisheries that provide food, jobs, and cultural sustenance to billions around the world.

Ocean pollution and you

The fate of our seas is not only up to the government or industry. Our individual, daily actions matter too. You can start by reducing water pollution and runoff at home, being more mindful of your plastic consumption, or organizing a cleanup of your local waterway. You can also support the work of NRDC and other environmental advocacy groups as well as businesses and organizations that work to preserve our coasts and waters.
This story was originally published on January 22, 2018, and has been updated with new information and links.

This NRDC.org story is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the story was originally published by NRDC.org and link to the original; the story cannot be edited (beyond simple things such as grammar); you can't resell the story in any form or grant republishing rights to other outlets; you can't republish our material wholesale or automatically-you need to select stories individually; you can't republish the photos or graphics on our site without specific permission; you should to let us know when you've used one of our stories.

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Ocean pollution in the form of fossil fuels, trash, offshore drilling, and noise is harming marine life. Learn what you can do to reduce harm to our oceans.

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Fish Get Risky Around Oil (Kalila Morsink)

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Fish Get Risky Around Oil (Kalila Morsink)

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"For a growing fish, crude oil exposure is really bad news. Even worse, the effects on fish behavior happen at quite low concentrations of oil, as little as the equivalent of a few drops in a swimming pool."

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Whether you are fish or human, taking risks is a part of life. But what happens when your inhibitions are lowered? In one study scientists found that zebra fish swimming around in water spiked with ethyl alcohol are less afraid of predators-for example, they're much slower to retreat from an attack by a robotic heron. Meanwhile, seeing other zebra fish makes them hyperactive. If you put one exposed zebra fish together with four unexposed ones, it will start swimming quickly around the tank, overreacting to the presence of other fish. Crazier yet, the other fish will be inspired to follow it.

Alcohol isn't the only chemical that can mess up fish behavior. Scientists studying ocean acidification, which is caused by carbon dioxide emissions, have found that fish swimming in low-pH waters are less afraid of potential predators, just like the fish exposed to ethyl alcohol. And now, a new study documents something else that's capable of befuddling fish-oil.

Oil gets dumped into the ocean at a rate of 343 million gallons a year. It gets spilled from tankers and barges, leaks out of pipelines, escapes from underground tanks, seeps out from the sea floor and-once in a while-it gets released millions of gallons at a time in an enormous spill. Specifically, fish are affected by certain toxic chemicals in crude oil, which humans release into the ocean all the time from cities, industrial shipping lanes and drilling exploration operations.

Both ethyl alcohol and oil make fish slow to respond to predators and more likely to take risks. Unfortunately, oil-addled fish don't "sober up," unlike zebra fish who have been given ethyl alcohol, which get back to normal behavior after a day. And the persistent increased risk-taking of oil-exposed fish might lead them to an early, untimely demise.

Dying young is a risk because it is in their embryo or larval stage that fish are most at risk from oil. Early in their lives, fish are still developing their organs and body regulation systems. Scientists already knew that exposing baby fish to crude oil could cause them to grow up with deformed hearts and spines, but they only recently found that exposure could also affect their brains.

(Jodie Rummer)

Working with six different species of fish from Australia's Great Barrier Reef, scientists found consistent-and discouraging-results. After being exposed to oil, juvenile fish exhibited behavioral defects that made it much more difficult for them to survive. Confronted with predators, they were less likely to seek shelter or flee into the company of other fish, and they were more likely to take risks that put their lives in danger. For a growing fish, crude oil exposure is really bad news. Even worse, the effects on fish behavior happen at quite low concentrations of oil, as little as the equivalent of a few drops in a swimming pool.

And what's bad news for fish is often bad news for the rest of the ecosystem. On coral reefs and elsewhere, fish are important links in the food chain that sustains higher-order predators (including humans) and keeps everything in balance. Worse, what affects fish might also affect other marine organisms-particularly those with a vulnerable larval stage, which includes everything from sea stars to snails to anemones. Based on this new research, scientists will have to keep an eye out for brain-related behavioral problems in fish exposed to oil as well as the other organisms they study. Better understanding these behavioral defects could be one part of the solution-although, of course, it doesn't address the oily source of the problem.

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The Ocean Portal receives support from the Gulf of Mexico Research Initiative (GoMRI) to develop and share stories about GoMRI and oil spill science. The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, For more information, visit http://gulfresearchinitiative.org characterization and remediation technologies.

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Whether you are fish or human, taking risks is a part of life. But what happens when your inhibitions are lowered? In one study scientists found that zebra fish swimming around in water spiked with ethyl alcohol are less afraid of predators -for example, they're much slower to retreat from an attack by a robotic heron.

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How Oil Spills Can Literally Break Fish Hearts. (Craig Welch)

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How Oil Spills Can Literally Break Fish Hearts. (Craig Welch)

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“We’re finding that oil can be toxic at far lower concentrations than we once thought and affect more organisms in more ways than we ever imagined.”

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Editor's Note: This is the second of four stories marking the fifth anniversary of the Deepwater Horizon oil spill in the Gulf of Mexico.

Oil-slathered birds were a potent symbol of the ecological cost of millions of gallons of oil that flowed into the Gulf of Mexico five years ago. But the less-visible plight of baby fish may offer a more far-reaching legacy.

Lab experiments show that trace amounts of the oil that gushed out of BP's blown-out well can cause birth defects in minnows, mess up the heart rhythms of young bluefin tuna, and dramatically slow the swimming speeds of amberjack and mahi mahi. These problems can disrupt their growth, trigger an early death, or curb their ability to chase food and escape predators.

The April 20, 2010, spill revealed so much about the toxic effects of oil that some experts now are rethinking the risks posed by potential spills in the Arctic Ocean and the polluted runoff of coastal cities.

"It's been paradigm-changing in a lot of ways," says Andrew Whitehead, an ecotoxicologist at the University of California, Davis. "We're finding that oil can be toxic at far lower concentrations than we once thought and affect more organisms in more ways than we ever imagined."

It's too soon to know what, if any, lasting impact the BP oil spill could have on fish. So far there has been no documented change in abundance of any Gulf species.

But oil is most harmful to fish when they're young, and scientists typically track populations using data from commercial catches of adults. Larvae of some Gulf fish, such as bluefin tuna, are slow-growing, so some of those exposed to the 2010 oil aren't yet big enough to be counted in nets-and may not be until they are eight years old.

"It'll take a long time before we'll know what's happening with the population," says Barbara Block, a tuna expert and marine biologist at Stanford University's Hopkins Marine Station.

Nevertheless, lab experiments, which used oil from the Gulf spill as well as 1989's massive Exxon Valdez spill in Alaska, suggest there's cause for concern-not just for those disasters but for any oil contaminating rivers and oceans.

Lessons From the Past

After the Exxon Valdez spilled millions of gallons into Prince William Sound, the numbers of pink salmon returning to the region's rivers plummeted and remained depressed for years. Pacific herring collapsed in 1993 and never came back.

In trying to grasp what happened, scientists learned that herring and salmon embryos near the spill accumulated polycyclic aromatic hydrocarbons (PAHs), toxic compounds found in oil. These chemicals, which are known to mutate DNA, visibly altered the shape and function of fish hearts in multiple lab experiments conducted over a decade.

"You have to put massive amounts of oil in water to kill an adult fish," says John Incardona, a fish toxicologist with the National Oceanic and Atmospheric Administration's (NOAA) Northwest Fisheries Science Center. "But an embryo doesn't have a liver yet, so they get hammered by these compounds at incredibly small doses."

When embryos were exposed in lab tests to high doses of PAHs, scientists reported heart failure. Those exposed to minute amounts of oil did grow into normal-looking fish-but they grew slower and often died early.

"When we exposed pink salmon to oil and released them to the sea, survival dropped by 40 percent long, long after exposure," says Ron Heintz, with NOAA's Auke Bay Laboratory in Alaska.

While the drops in wild salmon and herring in Prince William Sound after the Alaska spill were complicated by other factors, many scientists see a connection: "I definitely think oil played a role," Heintz says.

Incardona, who started his career as a pediatrician studying birth defects, wasn't done. He began treating fish as he would human patients.

"What do we do with people to test their heart?" he asks. "We put them on a treadmill."

He put zebrafish in tubes and measured their speed. Oil altered their hearts' rhythms, causing them to skip beats and change their shape. Fish also swam more slowly.

When the translucent herring embryos that had been exposed to small amounts of oil also were exposed to sunlight, the creatures died even faster. Ultraviolet radiation combined with oil caused the embryos to essentially disintegrate.

"In animals that have accumulated hydrocarbons and been subjected to UV radiation, that toxicity can be enhanced-dramatically," says Fern Galvez, a Louisiana State University biologist and toxicologist. "It can be ten times more toxic."

The 2010 explosion on the Gulf rig offered more clues about oil's toxicity.

No Population Impacts?

Scientists exposed many species to the oil that spilled from BP's well. Killifish, which are food for many Gulf species, hatched later and less successfully after oil exposure.

Researchers also turned to big, important mid-water predators-bluefin, yellowfin, marlin, swordfish. Many of these fish spawn in spring in the Gulf, producing floating egg sacks. In lab tests on tuna, Gulf oil affected development of everything from their jaws to their spines, all stemming from damage to the heart.

For major predators spawning in spilled areas of the Gulf, "l osses of early life stages were likely," a team of scientists, including several from NOAA, concluded.

Research like this study, which was published last year, is being used by the federal government to help build a legal case that will determine what BP should pay for ecological restoration in the Gulf.

BP representatives say the heart research didn't address key questions, such as how many larval fish actually were hit by oil in the Gulf.

"The authors themselves note that it is nearly impossible to determine the early life impact to these species," the company wrote in a statement.

A BP consultant also said too little was known about how many killifish embryos were exposed to oil for anyone to predict an impact on populations. Part of the region where Atlantic bluefin spawned, for example, was heavily oiled, but other parts were not. Plus fish populations are dynamic and capable of withstanding wide swings.

"I do not find the materials to offer a convincing prediction of population-level effects," Walter Pearson of Stantec Consulting Services wrote in a June 2014 comment.

The scientists responded that they suspected that oil industry officials would never accept that oil had harmed an entire group of fish without "a completely connected chain of causality."

"As a consequence, industry is unlikely to accept the findings of probable damage to fish populations from toxic chemicals, even when existing evidence is clearly consistent with such effects," they wrote.

The findings, however, have researchers looking for impacts beyond the Gulf.

How Low Can It Go?

For starters, the Gulf spill helped reveal that heart toxicity may be universal among fish exposed to oil. Researchers now see similar patterns in every fish they test in laboratories, from Japanese sea perch to olive flounder to Australian rainbow trout.

And they've learned it doesn't take much.

"The concentrations that reduce swimming performance are down at our detection limits," Incardona says. "So now the question is: What's the lowest concentration of oil that will cause a malformed heart?"

The question is important, scientists say, because one of the biggest threats to coastal waters is the steady drip of urban runoff as rains flush oil and other pollution off streets into rivers and bays.

"The implications are global," says Nat Scholz, ecotoxicology manager at NOAA's Northwest lab. "These compounds are ubiquitous. With rampant coastal development worldwide and use of motor vehicles and exhaust, and oil and grease leakage, you have lots of sources."

When we exposed pink salmon to oil and released them to the sea, survival dropped by 40 percent long, long after exposure.

Already, NOAA and the Environmental Protection Agency are trying to develop new strategies to reduce transport of runoff pollutants.

"The goal is to identify control measures that are inexpensive, effective, replicable, and scalable, and then get this information out to people who are dealing with stormwater issues," Scholz says.

The research also suggests oil spills in some places could prove worse than thought.

Before the Obama administration's recent move to open offshore oil drilling in the Arctic, a Bureau of Ocean Energy Management analysis found a spill the size of Deepwater Horizon 's was unlikely. But it also concluded there was a 75 percent chance of a significant spill over 77 years. If such a spill hit the wrong place at the wrong time, it could be felt widely.

Oil in cold environments sticks around longer, Incardona says, and the Arctic's ice-free summers offer greater potential for ultraviolet radiation to amplify toxicity for fish and wildlife.

"With that really clear water, the receding ice, those extended daylight hours, a summertime oil spill in the Arctic could be very bad," Incardona says.

A spill that harms one Arctic species could hurt many others. "If what you eat or what eats you gets nailed, you'll be affected," Whitehead says. For instance, almost everything at the top of the Arctic food web-seals, polar bears, many whales-eats cod.

"If you have a spill that poses a problem with Arctic cod, that's going to have major implications," Heintz says.

To prepare for possible oil spills in the far north, NOAA toxicologists are teaming with Norwegian scientists who raise Arctic fish so they can test them in labs.

"We're trying to get out ahead of the information gaps for Arctic species," Scholz says.
Follow Craig Welch on Twitter.

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How Oil Spills Can Literally Break Fish Hearts

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Editor's Note: This is the second of four stories marking the fifth anniversary of the Deepwater Horizon oil spill in the Gulf of Mexico. Oil-slathered birds were a potent symbol of the ecological cost of millions of gallons of oil that flowed into the Gulf of Mexico five years ago.

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How Plastic Pollution is Affecting the Ocean Wildlife (Kerry Taylor-Smith)

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How Plastic Pollution is Affecting the Ocean Wildlife (Kerry Taylor-Smith)

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"90% of seabirds have pieces of plastic in their stomachs"
"Current estimates suggest that at least 267 species worldwide have been affected, including 84% of sea turtle species, 44% of all seabird species, and 43% of all marine mammal species"

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How Plastic Pollution is Affecting the Ocean Wildlife

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A huge whale with a plastic bucket stuck in its mouth, new-born dolphin calves being exposed to pollutants through their mother's contaminated milk

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Using social media to strengthen public awareness of wildlife conservation

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Using social media to strengthen public awareness of wildlife conservation

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https://mce.nju.edu.cn/DFS/file/2019/12/30/201912301838394287ubwbz.pdf
Talks about how social media can impact the environment. Brings  up reason and explore them.
Wu, Y., Xie, L., Huang, S. L., Li, P., Yuan, Z., & Liu, W. (2018). Using social media to strengthen public awareness of wildlife conservation. Ocean & Coastal Management, 153, 76-83.

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Daoji, L., & Daler, D. (2004). Ocean pollution from land-based sources: East China Sea, China. Ambio, 107-113.

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https://en.wikipedia.org/wiki/Marine_pollution