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Besides being Richard Feynman's birthday, May 11 marks National Twilight Zone Day. The establisher of the holiday, as well as the reason this date was chosen, is appropriately murky (it's not the date the show first aired). We like to think that Feynman might have been amused by the association.

The term "twilight zone" didn't originate with the show, as the show's fan site The Twilight Zone Archives acknowledges:

The original phrase 'twilight zone' came from the early 1900s, used to describe a distinct condition between fantasy and reality. The phrase then evolved into a term used to define the lowest level of the ocean that light can reach, and then as an aeronautical term used by the U.S. Air Force. When Rod Serling was asked how he came up with the title The Twilight Zone, he replied, 'I thought I'd made it up, but I've heard since that there is an Air Force term relating to a moment when a plane is coming down on approach and it cannot see the horizon. It's called the twilight zone, but it's an obscure term which I had not heard before.' Our guess is that Serling had likely heard the term before, but had forgotten it; this premise is based on two facts-his experiences as a paratrooper in World War II, and from his brother, Robert Serling, who worked as an aviation editor for United Press International."

A 1999 Engineering column by Henry Petroski, " Daubert and Kumho," which discusses the concept of expert witnesses, quotes a 1923 court case about the admissibility of novel scientific evidence (in this case, lie detector tests):

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs."

In the July 1946 issue of American Scientist (long before the Twilight Zone show aired in 1959), Archibald Henderson of the University of North Carolina authored " Science and Art: An Approach to a New Synthesis."
In it, he states:

A philosopher with a deep insight into mathematics and the process of scientific and philosophic thinking, John Dewey, in his Art and Experience, has beautifully clarified and illuminated that twilight zone of creativeness where both artists and scientists function. The fault lies in a literal, unperceptive psychology which cannot or does not distinguish modalities in imagination, or nuances in intuition. In both artists and scientists, Dewey rightly maintains, "there is emotionalized thinking, and there are feelings whose substance consists of appreciated meanings or ideas."

A 2004 article, " The Lifestyles of the Trilobites," by Richard Fortey, returns to the original oceanography definition:

Some other strange, large-eyed trilobites may have lived at some depth in the water column rather than near the surface. Cyclopygid trilobites are bug-eyed forms that were generally wedded to a deep-water habitat, probably below 200 meters. They are often found in the company of blind trilobites that lived on the seafloor in deep waters, within sediments that accumulated at the edges of former continents or deep shelf sites. Studies of the eyes of these trilobites show that they are comparable to those of modern insects and crustaceans that live in dim light. So it seems likely that cyclopygids were animals of the mesopelagic region, the 'twilight zone' just below the ocean's photic zone, and their remains accumulated in death alongside bottom-living trilobites that had lost their eyes. Curiously, a few of these deep-water pelagic animals had square lenses, rather than the more-typical hexagonal ones, for reasons that have yet to be explained.

In 2006, the show itself inspired comparison to a real but barely conceivable location: the radioactive region around the melted-down Chernobyl nuclear reactor. In " Growing Up with Chernobyl," Robert Chesser and Robert Baker describe their research in the Chernobyl Exclusion Zone:

Although the 'Zone' was now nearly deserted-more than 135,000 people had been evacuated from the region-we were amazed by the diversity of mammals living in the shadow of the ruined reactor only eight years after the meltdown. The odd juxtaposition was eerily reminiscent of one of the creepier Twilight Zone episodes.

On a day that celebrates an iconic show that critically examined humanity, morals, and even sometimes modern technology, it seems fitting to look back at the term's scientific roots-and then to close the circle by considering its role as a fitting descriptor of what could arguably be seen as one of humanity's darkest technological episodes.

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Besides being Richard Feynman's birthday, May 11 marks National Twilight Zone Day. The establisher of the holiday, as well as the reason this date was chosen, is appropriately murky (it's not the date the show first aired). We like to think that Feynman might have been amused by the association.

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John, St; A, Michael; Borja, Angel; Chust, Guillem; Heath, Michael; Grigorov, Ivo; Mariani, Patrizio; Martin, Adrian P.; Santos, Ricardo S. (2016). "A Dark Hole in Our Understanding of Marine Ecosystems and Their Services: Perspectives from the Mesopelagic Community". Frontiers in Marine Science. 3. doi:10.3389/fmars.2016.00031

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National Institute of Aquatic Resources, Danish Technical University-Aqua, Charlottenlund, Denmark

AZTI-Tecnalia, Txatxarramendi Ugartea z/gZ/G, Sukarrieta, Spain

MASTS Marine Population Modelling Group, Department of Mathematics and Statistics, University of Strathclyde, Glasgow, UK

National Oceanography Centre, Southampton, UK

MARE, Department of Oceanography and Fisheries, University of the Azores, Horta, Portugal

European Parliament, Bruxelles, Belgium

In the face of increasing anthropogenic pressures acting on the Earth system, urgent actions are needed to guarantee efficient resource management and sustainable development for our growing human population. Our oceans-the largest underexplored component of the Earth system-are potentially home for a large number of new resources, which can directly impact upon food security and the wellbeing of humanity. However, the extraction of these resources has repercussions for biodiversity and the oceans ability to sequester green house gases and thereby climate. In the search for "new resources" to unlock the economic potential of the global oceans, recent observations have identified a large unexploited biomass of mesopelagic fish living in the deep ocean. This biomass has recently been estimated to be 10 billion metric tons, 10 times larger than previous estimates however the real biomass is still in question. If we are able to exploit this community at sustainable levels without impacting upon biodiversity and compromising the oceans' ability to sequester carbon, we can produce more food and potentially many new nutraceutical products. However, to meet the needs of present generations without compromising the needs of future generations, we need to guarantee a sustainable exploitation of these resources. To do so requires a holistic assessment of the community and an understanding of the mechanisms controlling this biomass, its role in the preservation of biodiversity and its influence on climate as well as management tools able to weigh the costs and benefits of exploitation of this community.

Introduction

One of the most understudied regions in the world oceans is the twilight zone (200-1000 m depth) which is the domain of the mesopelagic community. Lanternfishes (Myctophiids), which dominate the fish community, are a diverse group comprising around 245 species in 33 genera, distributed globally from polar to equatorial waters, with a maximum body size of 10-15 cm ( Paxton, 1979). Along with an associated community of mainly mesopelagic crustaceans and cephalopods Figure 1 ( Feagans-Bartow and Sutton, 2014), the community forms distinct acoustic scattering layers at around 500 m over large expanses of the ocean during day-time, ascending to the upper 150 m and dispersing at night (Figure 2). This diel migration has been referred to as the "largest daily migration of animals on earth" ( Hays, 2003; van Haren and Compton, 2013). The discovery of new species from viruses to large vertebrates is regular in this oceanic zone, supporting estimates of a million undescribed species living in the deep pelagic ( Robison, 2009).

Figure 1. Representative sample of mesopelagic fish including Maurolicus muelleri, Sergestes arcticus, and Benthosema glaciale and plankton e.g., Meganyctiphanes norvegica in the deep scatter layers of the Irminger Sea in November 2013.

Figure 2. Echograms from the Norwegian Euro-Basin cruise in May 2013, characterizing the distribution of the total backscatter, Sa values; see annotations (MacLennan et al., 2002), (upper panel) and the backscatter attributed to mesopelagic organisms (lower panel) at 38 kHz in the Irminger Sea, from Melle (2013). The diel vertical migration pattern of the community is clearly visible. The data has been processed according to standard IMR procedures using LSSS ( Korneliussen et al., 2006).

Resource strategists have identified the mesopelagic fish and plankton community, living in this twilight zone of the ocean (200-1000 m, depth), as a potential unexploited resource potentially contributing to the long term Blue Growth strategy set by the European Union, i.e., " smart, sustainable and inclusive economic and employment and growth from the oceans, seas and coasts", (e.g., Gjøsæter and Kawaguchi, 1980; FAO, 1997, 1998, 2001; Valinassab et al., 2007). Central to following a Blue Growth strategy for unlocking the potential of seas and oceans is the sustainable exploitation of the new resources provided by marine ecosystems tempered with the preservation of the existing services that the seas and oceans provide.

Despite the potential benefits, harvesting from this community (e.g., mesopelagic fish biomass recent estimates of 10 billion tons although still in question) is problematic and comes with a number of risks. For example, the community plays an integral role in carbon sequestration and thus climate regulation (e.g., Hidaka et al., 2001; Hudson et al., 2014) and is a key resource for higher trophic levels, serving as prey for marine mammals and key fisheries stocks such as tunas, billfish and sharks (e.g., Potier et al., 2007; Brophy et al., 2009) thereby influencing and maintaining biodiversity. Hence, the mesopelagic community potentially impacts upon traditional fisheries and ecotourism as well as climate via the biological carbon pump ( Davison et al., 2013). By exploiting this community, we can potentially produce more food for human consumption and nutraceutical products but there are potentially significant trade-offs related to climate regulation and conservation of biodiversity. Knowledge to assess these trade-offs is presently lacking and it is necessary to develop and apply an ecosystem based management framework for balancing the benefits, risks and trade-offs and to ensure sustainable management of the services that may be provided by the mesopelagic community. With this as the background, here we review some of the potential services, which the mesopelagic community can provide and the implications of exploitation.

Food Provision

Food insecurity is a major global issue, with human populations across much of central Africa and southeast Asia facing significant hunger today. Presentations at the COP 21 Agreements (2015) Climate Summit indicate that human adaptation of agricultural production systems and supply chains is unlikely to overcome this problem in the face of increasing global population and changing climate, even with the most optimistic emissions scenarios. Lanternfishes which dominate the fish community, have attracted attention as a potentially harvestable resource since the 1970's ( Gjøsæter and Kawaguchi, 1980; FAO, 1997, 1998, 2001). Some species are considered suitable for human consumption, but mostly the aim has been to supply the fishmeal market. The global biomass of this resource is very large, but just how large is uncertain, due in part to the poor sampling efficiencies of survey gears and partly to the low acoustic target strengths at the sonar frequencies needed to penetrate deep into the ocean interior ( Koslow et al., 1997; Kaartvedt et al., 2008; Heino et al., 2011; Davison et al., 2015). Hence, past and current estimates of the biomass of mesopelagic fish could be assumed to be an underestimate of that available. Early estimates of mesopelagic fish biomass were around 1 billion tons ( Gjøsæter and Kawaguchi, 1980), with one species Benthosema pterotum suggested to be one of the most dominant vertebrate species on earth ( Karuppasamy et al., 2007). Recent acoustic observations have suggested that this is a gross underestimate and that the true figure may be 10 billion tons ( Irigoien et al., 2014). Furthermore, at present there are no global estimates of the mesopelagic invertebrate community biomass (also suitable for meal production) though certain fractions have been intensively surveyed and assessed, in particular the Southern Ocean krill for which there is a well established fishery ( Constable et al., 2000). Although, there is an increase in the economic interest around mesopelagic resources, the biomass and yield potential and feasibility of exploitation has yet to be assessed.

What is the potential for contributing to human nutrition? Considering a human population on the order of 7.5 billion people this equates to 1.3 metric tons of mesopelagic fish biomass per human on the planet. Putting the estimate of Irigoien et al. (2014) into a food provision context, first we assume that harvested mesopelagic fish biomass is converted to food for human consumption via fish meal. Assuming that fish meal was the only source of raw material for aquaculture feed, and employing the conversion factors of Naylor et al. (2009; i.e., raw material input: aquaculture output of circa 4.0), global aquaculture production in 2014 of 67 million tons ( FAO, 2014) would require a harvested mesopelagic fish biomass of 268 million tons. This estimate represents circa 2.7 percent of the most recent global estimate of mesopelagic fish. In reality, vegetable protein is contributing an increasing fraction of aquaculture feed material, though there remains a need for wild-harvesting of essential fatty acids. As an academic exercise if we assume that 50% of the existing biomass (5 billion tons) could be sustainably extracted and converted to food for human consumption via use in the aquaculture industry without overfishing the community then, following Naylor et al. (2009), 5 billion tons of mesopelagic biomass could result in the production of circa 1.25 billion tons of food for human consumption. Given a human population approaching 7.5 billion this represents circa 4.6 kg of fish biomass per person per day at the present population level.

There are some caveats however. From an industry perspective, the Director General of IFFO (the Fish Meal and Fish Oil producers and consumer's organization), Andrew Mallison, has stated " The industry is certainly in need of more raw material - demand exceeds supply and demand is forecasted to continue growing as global aquaculture (and feed) increases. However, these deeper water fish will be more costly to harvest, and there would have to be a good set of science based harvest control rules to satisfy any environmental or ecosystem impact concerns. If the science indicates a potential sustainable fishery with a reasonable yield, there are several IFFO member companies who could look at the economics of fishing effort and return."

Nutraceuticals

Another key issue in human nutrition and aquaculture is the availability of nutraceuticals. The growth of nutraceutical products is partly based on a demand for "Omega-3" oils as human dietary supplements, and partly on the expanding aquaculture industry which has a requirement for n-3 LC-PUFA in feed material which can currently only be met from natural marine oils. Mesopelagic fisheries targeting nutraceutical-rich species to meet these demands are a new and emerging concept, convergent with the theme of Blue Growth. In the North Atlantic the prime example of an already operational commercial marine nutraceutical venture is "Calanus Oil," which is extracted from the copepod Calanus finmarchicustif, harvested in the coastal waters of the Norwegian Sea ( http://calanus.no/en/products/), and marketed in various forms as being rich in omega-3 fatty acids. Lanternfishes are recognized as being high in fatty acids (e.g., Lea et al., 2002). For example, recently, three species ( Diaphus watasei, Diaphus suborbitalis and Benthosema pterotum) from the NW Pacific haven been analyzed and found to have high levels of 20:5n-3 and 22:6n-3 fatty acids (icosapentanoic acid (EPA) and docosahexaenoic acid (DHA)). Thus Lanternfishes are a highly attractive source of raw material to support the manufacture of nutraceutical products ( Koizumi et al., 2014).

On the Blue Growth nutraceutical potential of mesopelagic fishes, the Director General of IFFO said " The nutraceuticals market does offer better returns for oil than animal feed-it would be interesting to know what loading of PCB's and Dioxin-like PCB's are present as some other North Atlantic fish oil sources require filtering. This incurs a greater cost than South American oils which are 'cleaner' but have to be shipped further to reach EU markets".

Hence, it seems that the Blue Growth potential of Lanternfishes exploitation may be at a cusp between an existing market (for bulk fishmeal) that seems to be barely profitable using exiting harvesting and processing approaches under existing demand conditions and an early-stage emerging market (for nutraceuticals) that could be profitable in the future ( Koizumi et al., 2014).

Climate Regulation

As is clearly outlined at the COP 21 meeting in Paris in 2015, "Parties should take action to conserve and enhance, as appropriate, sinks and reservoirs of greenhouse gases in order to do so an improved knowledge base for the assessment, monitoring and evaluation of the dynamics of carbon sequestration and thus climate regulation is necessary". The mesopelagic region of the ocean, and the community that inhabits it, plays a significant role in the global carbon cycle. The concentration of atmospheric carbon dioxide would be ~50% higher without the biological carbon pump (BCP) fixing inorganic carbon through photosynthesis by phytoplankton in the surface waters and "exporting" it to depth in the ocean ( Parekh et al., 2006). In the North Atlantic alone the BCP exports 0.5-2.7 GtC/year from the surface to depth ( Sanders et al., 2014). Models show that atmospheric CO ₂ concentrations can vary by ~100 ppm just by using the range of current observations for how deep the organic carbon penetrates before it is demineralized ( Kwon et al., 2009). The mesopelagic (100-1000m) is the region directly below the sunlit waters where photosynthesis can occur and the first region to be traversed by any "exported" organic material. The majority of organic carbon is respired in this region ( Giering et al., 2014). Its fate is controlled by interactions of the mesopelagic community. Only recently has it proved possible to balance the carbon budget in this region, by taking into account the trophic interactions of the organisms within it ( Giering et al., 2014). Our relative lack of understanding of this key region for climate regulation is further highlighted by other recent work (e.g., Jónasdóttir et al., 2015) showing that direct transport of organic carbon by higher trophic level organisms may be a substantial, but hitherto overlooked, pathway for the BCP. The seasonal migration to depth by copepods may result in a downward transport of organic carbon equivalent to that resulting from gravitational sinking in the sub-polar North Atlantic ( Jónasdóttir et al., 2015). Vertical migration and excretion/respiration by mesopelagic fish may also be significant. Regional studies have shown that such "active flux" can account for ~10-20% at depths near the top of the mesopelagic ( Davison et al., 2015) but may be as much as 70% near the bottom ( Hudson et al., 2014). Modeling predicts a decrease of ~40% in downward flux of organic carbon at 1000 m (the base of the mesopelagic) in the North Atlantic up to 2100 ( Yool et al., 2013). However, current global biogeochemical models, such as the one used for that study, do not include the active flux. The role of the mesopelagic community, particularly the higher trophic levels, in exporting carbon to depth in the ocean away from the atmosphere therefore potentially constitutes an order one uncertainty in how the BCP will respond to regulate climate over the coming century. Climate prediction models provide our primary tool for assessing potential risks posed by future change, the likelihood of such events happening and a testing way of mitigating against them. Modeled scenarios should also investigate the feedback from related pressures on the mesopelagic community: how will the mesopelagic community and the manner in which it processes organic carbon respond to projected changes in temperature, stratification, pH and oxygen? may there be impacts on climate if we over-exploit the mesopelagic fish stocks? The function of the mesopelagic community in the BCP is therefore a priority for biogeochemical research. Given that the service it provides is global with its activity predominantly carried out in the international waters of the deep ocean, research into and maintenance of the BCP is an international responsibility. For this reason, initiatives like the Galway Statement on Atlantic Ocean Co-operation (2014), and activities that it has already generated, such as the International Planning Workshop for a North Atlantic-Arctic Science Cooperation ( Benway et al, 2014), will be key in delivering the thorough investigation of the mesopelagic community's role in regulating climate that is needed.

Biodiversity

The participating Nations at COP 21 Agreements (2015) noted the "importance of ensuring the integrity of all ecosystems, including oceans, and the protection of biodiversity." Thus, Nations at COP 21 highlighted the need for improving our knowledge of the drivers of biodiversity and ecosystems, conservation restoration and sustainable management of the ecosystems, species and genetic diversity.

There is, however, a major lack of knowledge of the global composition and distribution of mesopelagic diversity, which is under-sampled and sparse in data (Figure 1). An additional problem is that we know very little about the function of mesopelagic biodiversity in the oceanic ecosystems and as providers of critical ecosystem services ( Robison, 2009). Potentially important ecosystem services are supported by a largely unknown deep pelagic biodiversity and interactions within the system ( Tittensor et al., 2010; Webb et al., 2010), which includes multiple components from microbes to marine megafauna interacting with mesopelagic fish and invertebrates. The ocean's deep interior remains an unexplored frontier. The regular discovery of new clades in this deep pelagic zone, which is estimated to hold a million of undescribed species, is subjected to the development of undersea technology providing unprecedented access, new capabilities, and new perspectives ( Robison, 2009). Present research on mesopelagic biodiversity is scarce thus a large gap in our understanding of the global distribution of overall mesopelagic diversity exists. Moreover, the biological adaptations of the organisms to the high stability of the mesopelagic environment make this ecosystem very vulnerable to pressures such as global fisheries and climate change.

This lack of knowledge impedes implementation of international agreements such as: (i) UN Resolution 61/1054 to conserve Vulnerable Marine Ecosystems; (ii) Aichi targets, related to the sustainable management of marine exploitation (applying ecosystem based approaches, avoiding adverse impacts on threatened species and vulnerable ecosystems and ensuring that the impacts of fisheries on stocks, species and ecosystems are within safe ecological limits); (iii) the Convention on Biological Diversity (2009), to identify ecologically or biologically sensitive areas; and (iv) the development of indicators required to assess the environmental status of marine ecosystems under different national and international legislation (i.e., Oceans Act, in US and Canada; Marine Strategy Framework Directive, in Europe; Regional Seas Conventions, worldwide; etc.).

Conclusions and Suggestions

The potential negative impacts of anthropogenic activities and climate change on marine ecosystems and human health must be addressed in a full realization of Blue Growth strategy of the mesopelagic. Exploitation of this community is a delicate problem in terms of the consequences for the ecosystem and its services. To tackle the global challenge of securing access to strategic but vulnerable food resources while coping with climate change risks, we need targeted innovation and sustainable development strategies that aim at preserving critical ecosystem services. This includes our oceans as providers, as claimed by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES http://www.ipbes.net). Hence, there is a need to improve resource management (through an ecosystem approach) and governance, to preserve them and to unlock their potential for the sustainable production of new products and industrial applications. To achieve this in relation to the mesopelagic community and its services we need knowledge on

(i) Population vital rates (e.g., recruitment, natural mortality and the effects of abiotic and biotic stressors on growth and survival) with respect to latitude and environmental conditions as the basis for stock assessments and population dynamics modeling to predict the sustainability of harvest rates.

(ii) Stock assessments to address fisheries policy. In the absence of a fishery, there are no existing data on which to base a conventional stock assessment, so we must use other methods relying on survey data and measurements of growth, maturity and natural mortality rates to generate assessments and forecasts of yields under different harvesting rates.

(iii) The links between oceanographic regimes and mesopelagic biomass and biodiversity (species, traits, population genetics and habitats) thus enabling the prediction of species dynamics relative to oceanographic regimes which will be impacted as their environment alters under climate change.

(iv) The role of the community in the food web, in particular the dependence of top predators on mesopelagic prey and thus their influence on fisheries and ecotourism.

(v) The role of individual species and the community in the sequestration of green house gases.

Clearly the potential benefits of harvesting the mesopelagic community is immense, however the consequences of mismanagement, unlike for most fish stocks, have global ramifications. Prior to exploitation a scientifically based ecosystem approach to exploitation is needed in particular focusing on the ecosystem and climate controls on the populations in order to avoid an overexploited state as is observed in many marine fish stocks (e.g., Worm et al., 2009; Branch et al., 2011). In this article, we have outlined the issues that need to be considered and the research that needs to be attended to prior to embarking on a Blue growth exploitation strategy in the mesopelagic zone of the oceans.

Author Contributions

All authors listed, have made substantial, direct and intellectual contribution to the work, and approved it for publication.

Funding

All authors were funded by their affiliated agencies.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank Drs. Webjørn Melle and Thor Klevjer from the Norwegian Institute for Marine Research for making the echograms and photographs presented in Figures 1, 2 available to the authors and the home institutes of the authors for providing the funding necessary to generate this article.

References

Paxton, J. R. (1979). Nominal genera and species of lantern fishes (Family Myctophidae). Contrib. Sci., Nat. Hist. Mus. LA. Cty. 332, 1-28.

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A Dark Hole in Our Understanding of Marine Ecosystems and Their Services: Perspectives from the Mesopelagic Community

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In the face of increasing anthropogenic pressures acting on the Earth system, urgent actions are needed to guarantee efficient resource management and sustainable development for our growing human population. Our oceans—the largest underexplored component of the Earth system—are potentially home for…

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P3 Fact:  microplastic ingestion by zooplankton

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P3 Fact:  microplastic ingestion by zooplankton

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19 that microplastics are ingested by, and may impact upon, zooplankton

Cole, Matthew; Lindeque, Pennie; Fileman, Elaine; Halsband, Claudia; Goodhead, Rhys; Moger, Julian; Galloway, Tamara S. (2013-06-06). "Microplastic Ingestion by Zooplankton" (PDF). Environmental Science & Technology. 47 (12): 6646–6655.

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MISC Fact: Life in the ocean’s ‘twilight zone’ could disappear due to the climate crisis

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MISC Fact: Life in the ocean’s ‘twilight zone’ could disappear due to the climate crisis

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Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.

One of Earth's largest habitats could see its rich diversity of life reduced by the end of the century due to the climate crisis.

The ocean's mesopelagic zone, also called the "twilight zone," is located between 656 feet and 3,280 feet (200 meters to 1,000 meters) below the surface.

The marine region, which accounts for approximately a quarter of the ocean's volume, is home to billions of metric tons of organic matter and some of Earth's most stunning biodiversity, despite being beyond the reach of sunlight.

The twilight zone also a crucial habitat for marine life that dives in search of prey, like sharks, or lanternfish that hide in the twilight zone during the day and swim to the surface waters to feed at night.

New research warns that the climate crisis could reduce life in the twilight zone between 20% and 40% by the end of the century. And if greenhouse gas emissions continue, the researchers estimate that the ocean region's life could be severely depleted within 150 years - and recovery may not be possible for thousands of years.

Ancient warm oceans

Paleontologists and ocean scientists teamed up to study the impacts on the ocean's twilight zone during previous ancient warming events in order to predict how the habitat may respond in the future due to global warming. The research team studied cores taken from the seafloor that included evidence of preserved microscopic shells from plankton.

Over time, the calcium carbonate shells accumulate on the seafloor, preserving information about what the environment was like during their lifetime. The tiny shells effectively create a timeline of how the ocean has changed over millions of years.

A study detailing the findings waspublished Thursday in the journal Nature Communications.

"We still know relatively little about the ocean twilight zone, but using evidence from the past we can understand what may happen in the future," said lead study author Dr. Katherine Crichton, a postdoctoral research fellow at the University of Exeter in the United Kingdom, in a statement.

The researchers focused on two warm periods that occurred 15 million years ago and 50 million years ago, where even ocean temperatures were "markedly warmer than today," according to the study.

"We found that the twilight zone was not always a rich habitat full of life," said study coauthor Paul Pearson, an honorary professor at Cardiff University in the United Kingdom, in a statement. "In these warm periods, far fewer organisms lived in the twilight zone, because much less food arrived from surface waters."

Particles of organic matter from the ocean's surface drift down and serve as one of the main food sources for life in the twilight zone. But past warming events caused the material to be degraded more quickly by bacteria, so less of it reached the ocean region.

Warmer ocean temperatures also increase the metabolic rates of organisms, leading to increased food demand and oxygen consumption, according to the study.

"The rich variety of twilight zone life evolved in the last few million years, when ocean waters had cooled enough to act rather like a fridge, preserving the food for longer, and improving conditions allowing life to thrive," Crichton said.

Luiz A. Rocha, curator and Follett Chair of Ichthyology at the California Academy of Sciences, worries that changes are underway that haven't been detected because the twilight zone is so understudied, largely due to a disconnect between funding and the costs of exploring this region.

Rocha, who was not involved in the study, researches the twilight zone and the mesophotic zone just above it, located between 98 and 492 feet (30 and 150 meters) below the surface.

"There are no baseline data to compare what we are measuring against, so this study that looks at the composition of the fossil record over time is one of the few ways we can try to understand how we are causing the twilight zone to change," Rocha said.

Predicting the future

Based on what they discovered from the ancient warming events, the researchers combined that data with Earthsystem mode simulations - modeling of Earth's carbon cycle as it moves through the land, sea and atmosphere.

The team's work revealed what is currently occurring in the twilight zone and how that might change in the future across decades, centuries and even millennia as the world warms.

"Our findings suggest that significant changes may already be under way," Crichton said. "Unless we rapidly reduce greenhouse gas emissions, this could lead to the disappearance or extinction of much twilight zone life within 150 years, with effects spanning millennia thereafter. Even a low-emissions future may have a significant impact, but that would be far less severe than medium- and high-emissions scenarios. Our study is a first step to finding out how vulnerable this ocean habitat may be to climate warming."

The researchers used three emissions scenarios based on the total carbon dioxide emissions after 2010.

The low estimate was 625 billion metric tons, medium was 2,500 billion metric tons and high was 5,000 billion metric tons.

The Global Carbon Budget estimates that the total global carbon dioxide emissions in 2022 was 40.6 billion metric tons. Yearly emissions have been close to that number each year since 2010, so the researchers noted that the low-estimate scenario they used has already been emitted.

The team thinks the medium emissions scenario will have been reachedin about 50 years, and the high estimate in just over a century.

"The twilight zone plays an important role in the ocean's carbon cycle because most of the carbon dioxide taken up by phytoplankton ends up there as their remains sink down from the surface ocean," said study coauthor Jamie Wilson, a postdoctoral researcher at the UK's University of Liverpool, in a statement.

INTERACTIVE: See what's at risk of disappearing on Earth

"One of the challenges of predicting how this movement of carbon might change in the future is that there are many processes to disentangle in the modern ocean. By looking back at the twilight zone in past warm periods we can identify the most important processes and use those to predict the future. We found that this natural cycling of carbon is likely already changing and may be perturbed long into the future."

The climate crisis has impacted Earth's oceans in the form of pollution, warming, deoxygenation, acidification and overfishing, according to the study. These effects have caused conservationists to consider different protective efforts, such as restricting harmful activities in the oceans.

Protecting the twilight zone will be difficult since typical conservation efforts, such as preventing fishing or deep-sea mining, can't apply there, Rocha said.

"A marine protected area for the (twilight zone) makes very little sense because the impacts that are affecting it are global in nature," he said. "What we really need to protect the (twilight zone) is to stop, or at least slow down, the high rate of change that we are subjecting our planet's climate to."

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Life in the ocean's 'twilight zone' could disappear due to the climate crisis | CNN

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The climate crisis poses a threat to the rich biodiversity of life that exists in the ocean's twilight zone, which exists just beyond the reach of sunlight. Life in this region could be reduced between 20% and 40% in the next 50 years, research warns.

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P3 QUOTE:  Marine Organisms in the Twilight Zone Under Threat of Warming Due to Climate Change

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P3 QUOTE:  Marine Organisms in the Twilight Zone Under Threat of Warming Due to Climate Change

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"By the end of the century, global warming is expected to reduce almost 40% of life forms within the twilight zone, formally known as the mesopelagic zone. This was reported from a study conducted by a group of researchers at the University of Exeter."

The Science Times
https://www.sciencetimes.com/articles/43639/20230508/marine-organisms-twilight-zone-under-threat-warming-due-climate-change.htm#:~:text=The%20Dark%20Side%20of%20Climate,at%20the%20University%20of%20Exeter.

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Marine Organisms in the Twilight Zone Under Threat of Warming Due to Climate Change

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Climate change poses risk to marine organisms within the ocean's twilight zone resulting to reduced life forms in the next 150 years. Learn more about it in this article.

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P3 QUOTE:  Fish are crucial in oceanic carbon cycle

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P3 QUOTE:  Fish are crucial in oceanic carbon cycle

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Fish may play a more important role in the marine carbon cycle than previously thought, a new study shows. Researchers have found that fish excrete prodigious amounts of a mineral, calcium carbonate, that had been thought to come almost exclusively from marine plankton such as shelled algae.

Kwok, R. Fish are crucial in oceanic carbon cycle. Nature (2009). https://doi.org/10.1038/news.2009.30

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fishing using the trawling technique poses a large threat to bycatch and the carbon cycling process.  It poses a risk to bycatch because trawl nets do not discriminate with fish, many types of unwanted fish could be caught in the net.
Fish also produce Co2.

Wikipedia mesopelagiz zone, Fishing

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☆Most mesopelagic fish migrate to the surface for food. Many fish feed on plankton, which are mixed with microplastics.

☆ research has shown that even zooplankton are consuming the microplastics themselves.

☆Mesopelagic prey fish play an important role in the food chain. Predators will be affected and the whole food chain will be contaminated.

☆ In 2018, approximately 73% of approximately 200 fish sampled in the North Atlantic had consumed plastic.

Wikipedia mesopelagic zone

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One of the most critical issues is ingestion of plastic debris, specifically microplastics.

Wikipedia mesopelagic zone

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"Marine debris, specifically in the plastic form, have been found in every ocean basin"

Wikipedia mesopelagic zone

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Mean particle sinking rates are 10 to 100 m/day.
The variability in sinking rates is due to differences in ballast, water temperature, food web structure and the types of phyto and zooplankton in different areas of the ocean.[13] If the material sinks faster

Wikipedia

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The mesopelagic zone occupies about 60% of the planet's surface and about 20% of the ocean's volume, amounting to a large part of the total biosphere.[2] It hosts a diverse biological community that includes bristlemouths, blobfish, bioluminescent jellyfish, giant squid, and a myriad of other unique organisms adapted to live in a low-light environment.

Wikipedia

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There is so much biomass in this migration that sonar operators in World War II would regularly misinterpret the signal returned by this thick layer of plankton as a false sea floor.[18][19] Estimates of the global biomass of mesopelagic fishes range from 1 gigatonne (Gt) based on net tows to 7–10 Gt based on measurements using active acoustics
The mesopelagic is home to a significant portion of the world's total fish biomass.
with exceptions in the Arctic Ocean.
mesopelagic fish biomass at about one billion tons.
A more recent study concluded mesopelagic fish could have a biomass amounting to 10 billion tons

Wikipedia

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The temperature variations are large; from over 20 °C (68 °F) at the upper layers to around 4 °C (39 °F) at the boundary with the bathyal zone.[5] The variation in salinity is smaller, typically between 34.5 and 35 psu.
The Sound Fixing and Ranging (SOFAR) channel, where sound travels the slowest due to salinity and temperature variations, is located at the base of the mesopelagic zone at about 600-1,200m.
euphotic zone where light promotes photosynthesis.

Wikipedia

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The mesopelagic zone is found from 600 to 3,000 feet (200 to 900 meters), where only about 1 percent of sunlight penetrates. It is not completely dark, but there is not enough sunlight to power photosynthesis. That means that the water at these depths contains less oxygen than the layers closer to the surface.

"Ocean Zones." UXL Encyclopedia of Science, edited by Amy Hackney Blackwell and Elizabeth Manar, 3rd ed., UXL, 2015. Gale In Context: High School, link.gale.com/apps/doc/CV2644300711/GPS?u=farm12971&sid=bookmark-GPS&xid=ebc49f8a. Accessed 1 Aug. 2023.

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P1 QUOTE:  Diving into the Twilight Zone.

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P1 QUOTE:  Diving into the Twilight Zone.

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The Twilight Zone, known scientifically as the mesophotic zone, is an area of ocean between the shallows and the deepest, darkest depths. Here in the dimly lit waters, some 30-200 metres below the surface, researchers have found areas of 'forest' that stretch across the sea floor. Unlike the kelp beds and seagrass meadows that grow close to coasts,
mesophotic ecosystems,

It took weeks for Bardout and his team to find their first Arctic forest--the first, he believes, to have ever been studied.

arine animal forests are all formed from communities of filter-feeding animals,

These different species create a canopy on the ocean floor,

if all these ecosystems are interconnected, then the destruction of one of them could also have dramatic consequences for the others.'

Cottam, Bryony. "Diving into the Twilight Zone." Geographical, vol. 95, no. 6, June 2023, pp. 8+. Gale In Context: High School, link.gale.com/apps/doc/A751791036/GPS?u=farm12971&sid=bookmark-GPS&xid=1fb03534. Accessed 1 Aug. 2023.

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P2 QUOTE: The Disappearing Twilight Zone.

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P2 QUOTE: The Disappearing Twilight Zone.

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In the upper ocean, tiny plant-like organisms called phytoplankton convert carbon from the atmosphere into organic matter through the process of photosynthesis.

This formation of organic matter, along with other waste matter produced by ocean organisms, produces "marine snow." This helps initiate the ocean's complex food web as organic matter and other carbon-based products sink away from the surface and move through the depths of the ocean.

Twilight zone animals consume matter near the upper ocean during the night and return to the deeper waters during the day,
The study suggests that up to 40% of twilight zone creatures could disappear by the end of the century.

"The Disappearing Twilight Zone." Youngzine, 29 May 2023, p. NA. Gale In Context: High School, link.gale.com/apps/doc/A751979670/GPS?u=farm12971&sid=bookmark-GPS&xid=6345c454. Accessed 1 Aug. 2023.

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P2 QUOTE:  Light and fish behavior: the science behind our night-fishing tactics

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P2 QUOTE:  Light and fish behavior: the science behind our night-fishing tactics

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most of it has to do with capturing prey for food.
One example of chumming with light is the way that recreational swordfishermen tie light sticks to their leaders. Light sticks are transparent plastic luminescent cylinders that contain chemicals that react to produce light when mixed.
Swordfish have hit the Johnson-Sea-Link submarines on more than one occasion,
Other predators such as oilfish and night sharks are also attracted to light and often take bait on swordfish long-lines.
Other predators such as oilfish and night sharks are also attracted to light and often take bait on swordfish long-lines.
There is an entire community of animals that migrate from as deep as 3,000 feet to the surface every night as the sun goes down.
sunset and sunrise animals near the surface will be silhouetted and easy to find by predators,

Gilmore, R. Grant. "Light and fish behavior: the science behind our night-fishing tactics." Florida Sportsman, vol. 42, no. 9, Sept. 2010, p. 53. Gale General OneFile, link.gale.com/apps/doc/A237137389/GPS?u=farm12971&sid=bookmark-GPS&xid=183e1bbb. Accessed 1 Aug. 2023.

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P1 Thought:  Water depth vs. Light penetration

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P1 Thought:  Water depth vs. Light penetration

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Water depth vs. Light penetration

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The benthic realm includes all of the ocean floor and extends from the coast to the deepest parts of the ocean.

Newton, David E. "Ocean Zones." The Gale Encyclopedia of Science, edited by Katherine H. Nemeh and Jacqueline L. Longe, 6th ed., vol. 5, Gale, 2021, pp. 3180-3182. Gale In Context: High School, link.gale.com/apps/doc/CX8124401757/GPS?u=farm12971&sid=bookmark-GPS&xid=ef093353. Accessed 1 Aug. 2023.

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euphotic dysphotic
(“eu-” = good, “photo-” = light)
(“dys-” = poor)

Newton, David E. "Ocean Zones." The Gale Encyclopedia of Science, edited by Katherine H. Nemeh and Jacqueline L. Longe, 6th ed., vol. 5, Gale, 2021, pp. 3180-3182. Gale In Context: High School, link.gale.com/apps/doc/CX8124401757/GPS?u=farm12971&sid=bookmark-GPS&xid=ef093353. Accessed 1 Aug. 2023.

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"Ocean zones are regions of the ocean that contain distinctive plant and animal life."

Newton, David E. "Ocean Zones." The Gale Encyclopedia of Science, edited by Katherine H. Nemeh and Jacqueline L. Longe, 6th ed., vol. 5, Gale, 2021, pp. 3180-3182. Gale In Context: High School, link.gale.com/apps/doc/CX8124401757/GPS?u=farm12971&sid=bookmark-GPS&xid=ef093353. Accessed 1 Aug. 2023.

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Plants and algae in the pelagic zone directly or indirectly support most of the ocean’s animal life.
(epipelagic zone, 0 to 650 feet, or 0 to 200 meters)
pelagic zone is further subdivided by depth into the mesopelagic zone (650 to 3,280 feet, or 200 to 1,000 meters)

"Pelagic zone." Environmental Encyclopedia, edited by Deirdre S. Blanchfield, Gale, 2011. Gale In Context: Opposing Viewpoints, link.gale.com/apps/doc/CV2644151030/GPS?u=farm12971&sid=bookmark-GPS&xid=fe0a3721. Accessed 1 Aug. 2023.

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Waters of the open ocean, extending from the edge of the continental shelf. The zone is subdivided horizontally on the basis of conditions obtaining at different depths into the epipelagic, mesopelagic, bathypelagic, abyssalpelagic, and hadalpelagic zones.

Allaby, Michael. "pelagic zone." A Dictionary of Ecology. : Oxford University Press, , 2015. Oxford Reference. Date Accessed 1 Aug. 2023 <https://www.oxfordreference.com/view/10.1093/acref/9780191793158.001.0001/acref-9780191793158-e-6219>.

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Allaby, Michael. "ocean divisions." A Dictionary of Ecology. : Oxford University Press, , 2015. Oxford Reference. Date Accessed 1 Aug. 2023 <https://www.oxfordr

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The ecological regions into which the oceans are divided horizontally and vertically. Open water comprises the pelagic zone, the water adjacent to the ocean floor the benthic zone

Allaby, Michael. "ocean divisions." A Dictionary of Ecology. : Oxford University Press, , 2015. Oxford Reference. Date Accessed 1 Aug. 2023 <https://www.oxfordreference.com/view/10.1093/acref/9780191793158.001.0001/acref-9780191793158-e-6210>.

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The part of the pelagic zone of the ocean that extends from the base of the epipelagic zone,
The temperature at the bottom of the mesopelagic zone is 10°C and the pressure through the zone ranges from 2 MPa at the upper margin to 7–10 MPa at the base.

Allaby, Michael. "mesopelagic zone." A Dictionary of Ecology. : Oxford University Press, , 2015. Oxford Reference. Date Accessed 1 Aug. 2023 <https://www.oxfordreference.com/view/10.1093/acref/9780191793158.001.0001/acref-9780191793158-e-6197>.

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