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Macro-invertebrates are organisms without backbones, which are visible to the eye without the aid of a microscope.

Macro: means you can see it (unlike micro)
Invertebrate: has no backbone (like slugs, insects, crayfish)

In contrast a vertebrate has a backbone (like you, cows, fish, birds)

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See how we collect macroinvertebrates from the Tongariro River.

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Searching for critters in the Tongariro River

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The types of macroinvertebrates that are living in a river are a good indicator of the river’s health. In this video Krysia Nowak shows you what macroinvertebrates are living in the Tongariro River. I wonder what role they play in the river’s food web.

From the LEARNZ "Sustainable Wai - Exploring Taupō Freshwater Fishery" virtual field trip. More at http://rata.learnz.org.nz/summary.php?vft=freshwaterecology184

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Lessons

Bugs Don't Bug Me (Full Manual)

Teach all Bugs Don't Bug Me lessons. Experiences include learning about water quality, aquatic insects, invasive species, and adaptations through hands-on activities. Find additional printed resources, photos and a video below.

Bugs Don't Bug Me (Individual Lesson Plans)

For Grades K-6
Build-a-Bug Macroinvertebrate Mix and Match
Designed to help introduce students to aquatic macroinvertebrates and the adaptations that allow them to live in an aquatic environment.
15 - 20 min.
Macroinvertebrate Simon Says
This activity will introduce students to aquatic macroinvertebrates (primarily insects) and the major segments (the head, thorax, and abdomen) and differentiation between larval, nymph, and adult stages.
30 min
Macroinvertebrate Investigation Macroinvertebrate Graphing Activity
Introduces students to the adaptations of macroinvertebrates and their feeding habits.
30 min.
If Bugs Could Talk
Through collection and observation, students learn about macroinvertebrates.
30 min.
Water Pollution Graphing
Teaches students to describe and identify the quality of a stream site by analyzing the aquatic macroinvertebrates that live there.
30-45 min.

Introduces students to the link between aquatic macroinvertebrates, land use activities and water pollution.
30 min.

Teaches students the link between land use activities and water quality.
45 min.
Who Lives in the Water
Stream Side Science (Individual Lesson Plans)
Missing Macroinvertebrates
For Grades 5-12
Wetland vs. Stream Macroinvertebrates
Students will investigate the diversity in a specific water body through observation and charting. They will collect and observe macroinvertebrates in an aquatic system. 6.4.1 SEEd Connections available.
Aquatic Invasion!
Students make inferences about the quality of freshwater using macroinvertebrate data collected from local water systems and explain the factors that contribute to the presence or absence of a species.

To investigate various biomes through observation and comparison of the diversity of life, in particular, the specific number of species, biomass, and type of organisms.

Teaches the properties of invasive species and their effect on aquatic ecosystems.
60 min.

Pictures and Additional Printed Resources

The following printed resources are offered in pdf format (may take awhile to download):

For more information regarding macroinvertebrates, including data sheets and collection instructions, please refer to the Stream Side Science and Utah Stream Team manuals. Also see the USU Extension Aquatic Macroinvertebrate webpage.

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Bugs Don't Bug Me (Full Manual) Teach all Bugs Don't Bug Me lessons. Experiences include learning about water quality, aquatic insects, invasive species, and adaptations through hands-on activities. Find additional printed resources, photos and a video below. Build-a-Bug Macroinvertebrate Mix and Match Designed to help introduce students to aquatic macroinvertebrates and the adaptations that allow them to live in an aquatic environment.

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Connected 2017 Level 3 - Mahi Tahi

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by Bronwen Wall

How clean is the water in your river? Scientists are testing the health of the Maitai River. Find out what data they collect and what can be done to make our rivers cleaner and healthier for everyone.

Back to series
Return to top ^

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by Bronwen Wall How clean is the water in your river? Scientists are testing the health of the Maitai River. Find out what data they collect and what can be done to make our rivers cleaner and healthier for everyone. Back to series Return to top ^

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Open access peer-reviewed chapter

By Kenneth W. Cummins

DOI: 10.5772/intechopen.79913

Abstract

The worldwide study of stream ecosystems remains a topic of great interest, impacting methods and concepts critical to the preservation and management of global freshwater resources. Stream macroinvertebrates, especially aquatic insects, have served as one of the main pillars of inquiry into the structure and function of running water ecosystems. Stream macroinvertebrates have been used so extensively for over 100 years because they are universally present and abundant, can be readily observed with the unaided eye, (unlike algae and microbes) and are much less mobile than fish which can easily move to totally new locations. Although taxonomic identification has been the basis of analysis of stream macroinvertebrates, functional analysis now offers an additional tool that allows much more rapid analysis that can be accomplished in the field using simpler methodology.

Keywords

streams

macroinvertebrates

functional feeding groups

foods of stream invertebrates

surrogates for ecosystem attributes

1. Introduction

In 1970, Robert Pennak, the preeminent freshwater invertebrate biologist, held that the basic unit of all stream ecology studies should be species level taxonomy (personal communication). This view was shared by essentially all stream ecologists of the day. Given the condition of many stream ecosystems and the taxonomy of aquatic insects then and now [ 1] that was, and is, a severe impediment to the advancement of research on streams. An alternative approach, based on macroinvertebrate functional analysis, coupled with higher order taxonomy (family or, if possible, genus) was proposed to facilitate addressing stream ecosystem research questions [ 2, 3]. This functional analysis focuses on adaptations used by freshwater macroinvertebrates to acquire their food. In this approach, seven functional feeding groups (FFG) usually are coupled with their seven food categories. The relative abundance of the food categories matches with the relative abundance of the FFGs that utilize those food categories ( Table 1) [ 1, 3, 4, 5, 6].

Functional feeding groups (FFG)

Examples of taxa

Adaptations for acquiring food resources

Scrapers (SC)

Ephemeroptera: Heptageniidae,
Ephemerellidae Drunella
Trichoptera: Uenoidae, Glossosomatidae
Helicopsychidae, Psychomyiidae
Hemiptera: Corixidae
Coleoptera (larvae): Psephenidae, Elmidae
Gastropoda

Mandibles with knife-like leading edge in aquatic insects, and file-like radula in Mollusca that removes attached algae; in Ephemeroptera, alga removal may be assisted by front legs

Detrital shredders (DSH)

Plecoptera: Pteronarcyidae, Nemouridae,
Capniidae, Peltoperlidae, Leuctridae,
Taeniopterygidae
Trichoptera: Limnephilidae, Calamoceratidae,
Lepidostomatidae
Tipulidae: Tipula
Crustacea: Amphipoda, Isopoda, Decapoda

Chewing mouthparts, selection for softest portions of conditioned (colonized by microbes, especially aquatic hyphomycete fungi) vascular plant tissue

Gathering collectors (GC)

Ephemeroptera: Baetidae, Leptophlebiidae,
Ephemerellidae, Tricorythidae, Caenidae
Trichoptera: Leptoceridae, Odontoceridae
Coleoptera: Elmidae (larvae), Hydrophilidae (adults)
Diptera: Chironomidae Chironomini,
Orthocladiinae
Oligochaeta

Non-specialized mouth part morphology that facilitates sweeping fine FPOM into the mouth

Filtering collectors (FC)

Ephemeroptera: Isonychiidae
Trichoptera: Hydropsychidae, Philopotamidae,
Polycentropidae
Diptera: Simuliidae, Chironomidae, Tanytarsini
Mollusca: Sphaeriidae, Unionidae

Filtering fans or setae on front legs or silk nets or strands that trap FPOM from the passing water column

Herbivore shredders (HSH)

Lepidoptera: Crambidae, Noctuidae
Coleoptera: Cocinellidae Galerocella

Chewing moth parts and crochets (Lepidoptera) that hold plant in place while feeding

Predators (P)

Plecoptera: Perlidae, Perlodidae
Trichoptera: Rhyacophilidae
Odonata: Anisoptera, Zygoptera
Megaloptera: Corydalidae, Sialidae
Hemiptera: Belastomatidae, Naucoridae,
Coleoptera: Dytiscidae, Hydrophilidae (larvae), Dytiscidae (adults)
Diptera: Tipulidae, Tabanidae, Empididae,
Chironomidae, Tanypodinae

Crushing, piercing or grasping moth parts and/or front legs; active, with large eyes or ambush predators; with swimming hind legs, crawling legs or welts or prolegs

Therefore, by identifying a limited number of food categories supporting stream macroinvertebrates it is possible to arrive at the morphological and behavioral adaptations generally shared by groups of taxa (FFG) that are adapted to acquire each of the food resource categories [ 7].

2. Functional groups (FFG) and food categories

Stream macroinvertebrate FFGs are listed below and summarized in Table 1.

1. Scrapers (SC) have morphological-behavioral adaptations that enable them to scrape non-filamentous attached algae from substrates (coarse sediments, wood, or stems of rooted aquatic vascular plants) in streams or lake littoral zones.

2. Detrital shredders (DSH) are adapted to feed on terrestrial plant litter (coarse particulate organic matter (CPOM), primarily leaves or needles that have been entrained in the stream and conditioned (colonized by) microbes, especially aquatic hyphomycete fungi.

3. Gathering collectors (GC) have very generalized adaptations used to feed on fine particulate organic matter (FPOM) of particle size less than 1 mm FPOM) which they sweep up from depositional areas or crevices in flowing or turbulent where it has settled or been entrained.

4. Filtering collectors (FC) have adaptations that allow them to capture FPOM from the passing water in streams or resuspension by turbulence in lakes using morphological structures or silk capture nets.

5. Herbivore shredders (HSH) are adapted to feed on live rooted aquatic plants, primarily the leaves.

6. Herbivore piercers (HPCR) are adapted to pierce individual filamentous algal cells and suck out the cell contents (primarily Trichoptera, Hydroptilidae).

7. Predators (P) are adapted to catch and consume live prey by engulfing the prey or piercing and extracting the prey hemolymph.

Most genera of North American aquatic insects have been assigned to FFG categories in tables that appear after each taxonomic chapter in [ 1].

Parallel or convergent evolution has endowed differing taxonomic groups with similar morphological (e. g. mandible structure) and behavioral (e. g. net spinning and case construction) adaptations for acquiring a given food resource.

An example is the similar mandible structure found in larvae of four different scrapers (SC); three caddisfly (Trichoptera) genera representing three different families and one beetle (Coleoptera) genus, Psephenus, in the Family Elmidae are shown in Figure 1 [ 8]. All the mandibles have a knife-like leading edge which, when drawn across a rock or wood surface towards the mouth and remove attached algae. This material is contained and directed into the mouth by basil setae Figure 1. A further example is found in the mandibles of wood gouging detrital shredders (HSH) shown in Figure 2 [ 9]. Three different genera in three different families and orders are represented. The mandibles of these wood shredder aquatic insects are all three-toothed, scooped-shaped with basal setae. The mandibles are used to gouge grooves in the surface of wood entrained in a stream, ingest it and digest the microbes present that are the source of their nutrition. This poor quality food resource results in longer life cycles, especially the larvae of the beetle Lara that requires 5 years to mature. Often, Lara is found on long term stable large wood habitat in northwest, old growth conifer bordered streams [ 10, 11].

Many FFGs are restricted to a single mode of feeding. These obligate taxa maintain the same FFG mode of feeding, independent of the quality of the food being harvested [ 12]. A measure of the match between the FFG and the harvested food resource can be described by the efficiency of the conversion of food ingested to growth [ 4]. An example is the caddisfly Glossosoma nigrior (Trichoptera Glossosomatidae) [ 12]. Analysis of gut contents of two populations of G. nigrior occurring in two different streams, where they both fed as FFG scrapers, revealed that the ingested food differed significantly through all five instars of the growth period ( Figure 3) [ 9]. The G. nigrior population in the stream that provided good non-filamentous algal periphyton had gut contents totally dominated by algae. The pre-pupae in this population achieved significantly higher final dry biomass than the other population which had gut contents dominated by detritus. This second stream was in a canopy closed forest in which the rock surfaces were covered with fine detritus with little or no algal periphyton. The gut analysis method involving the use of Millipore™ filters is described in [ 13].

Facultative FFG taxa are not as fixed with regard to adaptations for acquiring food. The added flexibility in feeding allows for survival in a wider range of habitats that offer more food types but the conversion of ingested food to growth is less efficient than in obligate taxa. In their early instars, the majority of taxa are facultative generalists feeding on detritus, even predators like the megalopteran Nigronia [ 14].

A picture key to stream macroinvertebrate FFGs appears as an Appendix in [ 5].

Stream macroinvertebrate FFG food categories are listed below and described in Table 2 [ 4, 5].

1. Attached non-filamentous algae, primarily diatoms but also green or red algae.

2. Terrestrial plant litter (CP)M) entrained in the stream and colonized and conditioned by microbes.

3. Depositional FPOM on fine sediments in pools, stream margins or under or in crevices in coarse sediments in the current.

4. Suspended FPOM transported in the water column or suspended by turbulence.

5. Living rooted vascular aquatic plants.

6. Filamentous green algae.

3. Similar FFG adaptations in different taxa

Noel Hynes, arguably the premier stream ecologist of the last 60 years, observed that he could "turn over a rock in any clean stream the world over and recognize familiar aquatic insects, but they were all in different families" (personal communication). An example is the very similar dorsal-ventrally flattened body form of a North American scraper mayfly (Ephemeroptera, Heptageniidae) and a Brazilian mayfly (Ephemeroptera, Leptophlebiidae) ( Figure 4) [ 9, 15]. Both these scrapers primarily use the mandibles to remove attached periphytic algae from rock surfaces. The mandibles of different taxa functioning as scrapers are similar: a cutting ventral edge with basal setae that keep the algae confined as it is moved into the mouth ( Figure 1). Another example of similar feeding structures was described above for wood-gouging shredders belonging to different taxa ( Figure 2). All these examples represent parallel or convergent evolution resulting in differing taxa being adapted to acquire the same food resource type.

The FFG of a given taxon can vary with age (instar in aquatic insects). There is evidence that essentially all aquatic insects are gathering collectors in the first (and second in some) instars. For example, Petersen [ 14] documented through gut analysis that the first instar of the predaceous megalopteran Nigronia serricornis (Corydalidae) fed on FPOM as a gathering collector. Taxa can also switch FFG as they progress through the growth period. The limnephilid caddisfly (Trichoptera) Pycnopsyche lepida switches from feeding on conditioned CPOM leaf litter as a detrital shredder in the first four instars to a scraper in the fifth (final) instar. This transition is readily discernable because in the first four instars the larvae construct an organic case made of leaf sections and fine sticks that are readily available in the litter accumulations where the larvae occur. In the fifth instar the larvae move into fast water where the feed by scraping periphytic algae from cobbles in flowing water. At that time, the larvae convert to heavier mineral cases [ 15, 16].

4. Benefits of FFG analysis

There are two significant benefits in the FFG approach. First, it allows stream macroinvertebrates collected live in benthic or drift samples to be placed in ecologically relevant categories using only the level of taxonomy needed to separate them [ 6]. Simple examples would be: all Odonata dragonfly and damselfly nymphs are predators (P) and stone case-bearing Trichoptera (caddisfly) larvae are scrapers (SC) while those in organic cases (leaf and stick/stem material) are detrital shredders (DSH). These examples, in which ordinal taxonomy is all that is required, are used in the key given in Merritt et al. [ 5]. Clearly, the more taxonomic resolution the better, but the FFG allows typical volunteer or class groups to gather useful data on aquatic ecosystems of local concern. And, importantly, the data can be taken on site using live specimens that allow behavioral and color paten traits, that are lost or fade in preservation, to be used in the evaluation. Furthermore, the collected organisms can be preserved and returned to a laboratory, if accessible, when detailed taxonomic determinations are required, for example to calculate diversity indices (e. g. see ecological tables in [ 1]).

The FFG detrital shredders (DSH) are reliably linked to the inputs plant litter from the riparian zone [ 17] that can be studied easily with the use leaf or needle packs which accurately mimic how plant litter is naturally processed by fungi and detrital shredders (DHS) in streams [ 18]. These are prepared using leaves or needles of trees that are present in the riparian zone of a stream under study ( Figure 5) [ 8, 18]. Dry leaves or needles are weighed into 10 g amounts (to nearest 0.01 g) and soaked in warm water until soft (5-10 minutes). When the leaves are soft enough to handle so that they do no break, they are gathered into a packs and stapled together with the plastic Tees using a Buttoneer™ gun. The needles are threaded into a chain on monofilament fishing line ( Figures 5 and 6). Each leaf or needle pack is fastened to an elastic band of sufficient size so that it can be attached to a common brick ( Figure 6). The packs, one or two to a brick ( Figure 6), are placed in the stream facing into the current to simulate the obstructions against which plant litter accumulates in streams in the current. It is important that some flow occurs across the surface of the leaves or needles to maintain dissolved oxygen levels required by the obligate aerobe aquatic Hyphomycete fungi that colonize the plant material and constitute the major source of the nutrition for detrital shredders (DHS) [ 19]. The leaf pack shown in Figure 6 are hickory leaves that were incubated in a third order woodland Michigan stream in October for 2 weeks at 10°C. The effect of the shredder feeding is evident. The softer, most heavily fungal colonized portions of the leaf have been used [ 20, 21]. The detrital shredders (DSH) select portions of the leaves or needles that are most heavily colonized by aquatic hyphomycete fungi. Specific polyunsaturated lipids of the fungi attract the shredders [ 19].

The second benefit of using the FFG approach is that ratios of the number of specimens collected in each FFG category can be used to describe a stream reach and compare it to other reaches and other streams ( Table 3) [ 5, 8]. Because these ratios are dimensionless numbers, they are relatively independent of sample size. For example, it has been demonstrated that the relative number of scrapers collected from one rock in a given stream riffle is not statistically different from the collection from five rocks in the same riffle [ 9]. Some FFG ratios that can serve as surrogates for stream ecosystem attributes are summarized in Table 4. Threshold ratio values (percentages) have been proposed based on field evaluations that can serve as surrogates to ecosystem attributes such as the classification of a stream reach as autotrophic (i.e. dependent on in-stream primary production as the primary energy source) vs. heterotrophic (dependent on riparian out of steam primary production as the primary energy source) ( Table 4) [ 22, 23, 24, 25]. This particular ratio (SC + HSH/DSH + SC + FC) is a surrogate for directly measured P/R, which is the ratio of gross primary production to total community respiration (i. e. including autotrophs). P/R, which is measured by monitoring oxygen levels over time across a stream reach or in enclosed in situ chambers [ 26]. The FFG surrogate P/R ratio is strongly influenced by season and like other FFG ratios might require a different threshold for spring-summer vs. fall-winter ( Table 4).

Stream ecosystem attributes

Name of FFG surrogate ratio

Definition of FFG surrogate ratio

Ratio name

FFG surrogate ratios

Proposed thresholds and explanations

Interpretations

Autotrophy-heterotrophy index

SC + HSH + APC to DSH + GC + FC

FFG ratio of >0.75 corresponds to a directly measured P/R = 1.00. Represents in stream plant (algae and vascular) production > than riparian plant litter inputs (or total respiration of microbes + plants and animals)

Stream energetics driven by periphytic algal + any vascular plant production as compared to riparian plant litter inputs

Shredder index

DSH + HSH to GC + FC

FFG ratio of >0.50 in fall-winter or >0.25 in spring-summer. Represents CPOM shredder food availability > FPOM collector food availability

CPOM food support for shredders > than FPOM for Collectors. Fall-winter litter inputs usually >spring-summer and condition more rapidly

Filtering collector index

FC to GC

FFG ratio of >0.50 indicates suspended FPOM load > storage (entrained) FPOM

FPOM food for collectors at higher density and/or better quality than storage FPOM

Habitat stability index

FC + SC + HSH to DSH + GC

FFG ratio of >0.50 indicates that stable locations for scraping and attachment are in greater abundance than shifting unstable substrates

Filtering collectors require stable locations for attachment and construction of capture nets and scrapers require surfaces that remain in a stable position facing up

Top down predator index

P to total FFGs

Predator to prey ratio 0.10-0.20 to total macroinvertebrate population

This level of predator population density (or biomass) allows for sufficient prey to support them. If predators >20% probably indicates populations of rapid turnover (polyvoltine prey populations present

In the case of detrital shredders (DSH), their presence and abundance depends on the type of plant litter inputs and season. If the riparian zone is dominated by deciduous hard woods, the inputs are in the fall-winter period. Hardwoods, except oaks, are conditioned rapidly by aquatic hyphomycetes and fed on by shredders. Conifers (evergreens) shed foliage primarily in the spring-summer and conditioning by fungi is much slower and shredder feeding is delayed. Prairie Creek in Redwood National Park, California provides an example from an old growth conifer forest stream with slow fungal conditioning and delayed detrital shredder (DSH) activity ( Table 5 [ 27]). The riparian derived CPOM is largely wood and conifer needles which require along conditioning times before shredders begin feeding. This suggests that samples taken in December were too early to detect the major shredder activity. The shredder caddisfly larvae (Trichoptera: Lepidostoma and Gumaga) and stonefly Nymphs (Plecoptera: Peltoperlidae, Capniidae, Leuctridae) that were collected were quite small. The mean dry mass per individual, of the 34 individuals collected was 6.6 mg (caddisflies 111 mg, stoneflies 75 mg) indicating very early instars. The ratio was low because the biomass of the GC (0.061 mg) plus FC (3.35 mg) was much greater. The recommended threshold for conifer old growth forest streams should be based samples for February or March. The general 0.50 threshold was based on data from deciduous forest streams taken in the fall when the conditioning of the riparian litter was sufficient to accommodate expected shredder populations [ 18].

Stream FFG ratios

Calculated ratios

Proposed thresholds

Stream ecosystem interpretations

P/R index: (SC + HSH/DSH = GC = FC)

0.96

0.55

Ratio > 0.75 (autotrophic)

SC numbers indicate a significant algal periphyton based autotrophic stream ecosystem (significant biomass of stonefly and caddisfly shredders indicate heterotrophic system supported by riparian plant litter inputs)

CPOM shredder index: (DSH/GC = FC)

0.15

0.04

Ratio > 0.50 (predicted fall-winter shredder component)

The predicted range for fall-winter shredder populations not met.
(supply of sufficiently conditioned [colonized by microbes] riparian plant litter inputs, not adequate)

FPOM suspended load index: (FC/DSH + GC + FC)

0.14

0.28

Ratio > 0.50 (sufficient FPOM to support filtering collectors, assuming sufficient quality)

The amount, or quality (e.g.. organic content) of FPOM in suspension and transport below typical levels to support FC populations (this old growth conifer forest stream dominated by slowly processed wood and litter likely generated only primarily low amounts of poor quality FPOM; rapid turnover deciduous litter from big leaf and vine maple probably absent)

Channel stability index: (SC + FC + HSH/DSH + GC)

1.09

0.96

Ratio > 0.50 (sufficient stability to support SC and FC populations}

Stable substrates, coarse sediments and large wood, well above levels predicted to support surfaces required scraping and filtering macroinvertebrates (large wood in old growth forest streams observed to provide a long term stable habitat)

Top down predator index: (P % of total)

0.15

0.21

Ratio > 0.10 < 0.20 (predicted predator top down control of macroinvertebrate populations)

Both numerical and biomass estimates of predators fall within the expected % r of the macroinvertebrate community (all the expected predators present; stoneflies, especially the large Perlidae, Tipulidae [except Tipula], and Tanypodinae midges)

There is an extensive literature using FFG analyses, for example the numerous references cited in the ecological tables that accompany each aquatic insect order in [ 1]. FFG analyses and the ratio method, including proposed thresholds have been used to evaluate Florida Rivers. FFGs were used to characterize the un-dammed reach of the Kissimmee River as a model for general restoration of the 100 miles of the channelized River [ 22]. The ratio method was employed to characterize the remnant oxbows of the Caloosahatchee River according to their ecological attributes and to provide recommendations for preservation and restoration of the River's oxbows [ 25]. Floodplain (marsh) habitats of the St. John's River were also evaluated relative to hydrological influences using FFG surrogate ratios to predict the effects of water withdrawal from the river [ 25]. The method also was used to characterize the ecological conditions in a wide range of Brazilian streams and rivers [ 24].

5. Conclusions

Proposed in this chapter is the use of the FFG method of analysis to gain rapid and efficient insight into macroinvertebrate community composition and fits unction in freshwater ecosystems. The method should be compatible with a broad level of expertise, from beginner to advanced, and can be conducted stream-side allowing live animals to be released or preserved and returned to the lab. If the FFG ratio method is to be used, at least some qualitative observational data should be recorded: riparian information about the dominant vegetation cover (e. g. percent deciduous vs. evergreen) and the % canopy closure; dominant stream habitat (riffles vs. pools, coarse vs. fine sediments, % accumulation plant litter such as leaf packs); discharge level relative to bank full (the permanent vegetation line)and general land use observations (e. g. agricultural or live stock grazing, timber harvest or other human disturbances). When conducting FFG analysis it is most useful to collect, and keep separate, samples from three types of habitat: Riffles (coarse sediments), pools (fine sediments), and plant litter accumulations. Samples can be taken with timed (e. g. 15 s) D-frame or aquarium net samples. The data can be combined later into a "composite" sample, but the relative importance of each habitat can be assigned based on the qualitative evaluation of the % stream bottom cover of each habitat type. Most importantly, The FFG analysis technique does not foreclose on any traditional use of taxonomic analysis of the samples in the laboratory.

Acknowledgments

Thinking back to 1973, I first became fascinated with adaptations of freshwater macroinvertebrates, especially in streams. Herb Ross Illinois Natural History Survey) invited me to submit a contribution to the Annual Review of Entomology. He said there were rarely any papers on aquatics and suggested I consider ecological adaptations of aquatic insects as a topic. At about the same time, Noel Hynes (University of Waterloo, Canada) told me he could turn over a rock in any stream in the world and recognize the mayfly nymphs, but they were all in the "wrong family." This example of convergent or parallel evolution formed the basis for the functional feeding group approach. During the intervening years, a monumental array of colleagues has been instrumental in my understanding of freshwater macroinvertebrates. George Lauff (at the University of Michigan) directed my PhD work and Rich Merritt (Michigan State University) and Peggy Wilzbach (Humboldt State University, CA) have provided ideas and encouragement for decades.

Kenneth W. Cummins (November 5th 2018). Functional Analysis of Stream Macroinvertebrates, Limnology - Some New Aspects of Inland Water Ecology, Didem Gökçe, IntechOpen, DOI: 10.5772/intechopen.79913. Available from:

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Functional Analysis of Stream Macroinvertebrates | IntechOpen

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The worldwide study of stream ecosystems remains a topic of great interest, impacting methods and concepts critical to the preservation and management of global freshwater resources.

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From 17 - about 24 min, good description of mayfly life cycle. From about 60min stonefly.

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Did you know that a bug is not an insect and an insect is not a bug? Did you know that mayflies like to dance and make love too? Ever wonder what fly to tie on during that blizzard hatch? We have the answers and more on this podcast with one of our dearest friends Joe Slusark. Joe is a entomologist from Chico State, for over 20 years Joe has been living his dream wading chest deep into the world of entomology. Join us as we talk fishing and bugs with one of the coolest guys we know and have the pleasure of fishing with, Joe Slusark.

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Bug Porn - Joe Slusark - The Barbless Fly Fishing Podcast

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Did you know that a bug is not an insect and an insect is not a bug? Did you know that mayflies like to dance and make love too? Ever wonder what fly to tie on during that blizzard hatch? We have the answers and more on this podcast with one of our dearest friends ...

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New Zealand has over 200 species of freshwater macroinvertebrates. An invertebrate is an animal that lacks a backbone. 'Macro' means the invertebrates are large enough to be seen without magnification - even though some can be as small as 1 mm in length. Examples of aquatic macroinvertebrates include crustaceans (such as sand hoppers), insects (such as beetles and mayflies), molluscs (such as snails) and segmented worms (such as leeches).

Habitats

Freshwater macroinvertebrates live in all kinds of freshwater environments, from pristine mountain streams to wetlands to sewage ponds. They make their homes under rocks or leaves, in the sediment or in the vegetation along the sides of the waterway. Some creatures, like freshwater snails and mussels, spend their entire lives in the water. Other creatures, like dragonflies and mosquitoes, live in the water during their larval or nymph stages but out of the water as adults.

Waterways - especially streams - have different types of 'bottoms' or substrates. Hard bottoms are made up of rocks or gravels. Soft-bottomed waterways tend to be muddy or weedy. Burrowing creatures like worms prefer to live in the softer substrates.

Aquatic food webs

Some macroinvertebrates are carnivorous - they feed on other creatures in the water.

Some graze on algae - rather like guinea pigs nibble the grass. Other macroinvertebrates are filter feeders. They ingest tiny pieces of food suspended in the water.

Macroinvertebrates are an important food source for fish, birds and other animals. They also help to recycle nutrients in aquatic environments.

Physical adaptations

Macroinvertebrates have physical adaptations suited to living in specific aquatic environments. Creatures that live in fast-flowing water, like stoneflies and mayflies, often have claws or hooks for holding on to rocky substrates. Water boatmen live in slow-moving water so their legs are designed for swimming rather than holding on. The spiny-gilled mayfly has hairy legs to trap drifting food particles.

Some macroinvertebrates breathe through gills. Others, like diving beetles, trap air bubbles under their exoskeletons. Gill location (on the body, legs or even on the tail) helps scientists to identify different species.

Human impacts on macroinvertebrates

Humans modify the land to build cities and farms. We dam rivers to produce electricity and divert streams to build roads. These changes have impacts on macroinvertebrates. Clearing vegetation from the banks removes food sources, breeding grounds and shade - so the water gets warmer. Dams, weirs and irrigation reduce water flow and velocity - causing sediments to build up, altering the substrate and making it difficult for gilled creatures to breathe. Nutrients from sewage or farm run-off alter the types of plants that grow in waterways. When the plants die, they use up dissolved oxygen and cause eutrophication. Spills and run-off from business and residential areas also change the water chemistry.

Nature of science

Water quality indicators

Many freshwater macroinvertebrates are trapped or confined to their particular habitat. They are unable to migrate or move to a new location if changes occur. For this reason, macroinvertebrate species identification and counts are often part of water quality surveys. Sensitive creatures like caddisflies and mayflies are associated with good water quality, whereas more tolerant creatures like snails and worms can survive in modified or degraded streams with poorer water quality.

Regional councils and water care groups monitor streams over time to develop baseline information about macroinvertebrates and water quality. Changes in species type or number may indicate changes to stream conditions, both good and bad. Other indicators like water clarity, temperature and water flow/velocity are also monitored.

Read about monitoring and restoration projects in these articles: Students help restore mauri to the Oruarangi Stream, Riparian restoration and Water quality in Rotorua lakes.

Macroinvertebrates are bioindicators. Read more about this concept in the article Bioindicators.

Related content

Useful link

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New Zealand has over 200 species of freshwater macroinvertebrates. An invertebrate is an animal that lacks a backbone. 'Macro' means the invertebrates are large enough to be seen without magnification - even though some can be as small as 1 mm in length.

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Ok, so we're not sending you down to a river, but you can still see what kinds of invertebrates are in your own back yard! Build one of these traps and see what moves in!

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To take a census you need to trap and then count the bugs and beetles, but don't do this too much as they don't like being disturbed.

1. Follow the rules for bugs and crawlies

Handle them carefully.

Look, identify, count and record.

Return them to where you found them. (This is tricky because you will be using traps. You will have to make a studied guess because they will walk from somewhere to get to your trap!)

2. Make a trap for your bugs and crawlies

Mighty trap 1 - the potato trap

Get a big potato and cut it in half.

Scoop out some of the insides with a spoon to make a room.

Close the potato and make an entry hole to the room inside.

Place your potato trap half buried in the soil and leave it for three days.

The even mightier trap 2 - the pitfall trap

Create a pitfall trap like this one

These traps are so mighty you need to check them every few hours. You could set a few traps in different parts of your backyard but draw a plan of where you placed them so you can remember.

All you need is an empty plastic bottle.

Put holes in the bottom of the plastic bottle to let water out.

Cut off the top of the bottle and turn it upside down inside the bottom of the bottle as the picture shows.

Place a stick inside the bottle to let the critters out when you are not using the trap.

3. Identify, count and record your bugs and crawlies for the census

To look at your invertebrate you need:

A magnifying glass or hand lens.

A white ice-cream container so you can see the bug or beetle against a white background.

You can move your critters by:

Picking them up gently in your hand.

Using a paintbrush.

To record your invertebrates you should write down the date, the trap number, the types of beasts you've found and how many you've found of each type.

Do another census in a few weeks. Do it at the same time of day and in the same conditions as your first census. Compare the numbers with your first census and see if your insect and bug population is growing.

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To take a census you need to trap and then count the bugs and beetles, but don't do this too much as they don't like being disturbed. Handle them carefully. Look, identify, count and record. Return them to where you found them. (This is tricky because you will be using traps.

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Supports learning about insects for ECE & early primary.

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How to measure river or stream health using invertebrates

Benthic invertebrate communities are widely used as indicators of stream ecosystem health because they include a wide range of species, each with relatively well-known sensitivity or tolerance to stream conditions. The most common stream health indices are taxa richness, percentage of EPT taxa and the macroinvertebrate community index (MCI).

Taxa richness

Taxa richness is considered a very coarse indicator of stream health, which is measured by counting the number of different species of invertebrates present in a sample. The benthic invertebrate community typical of pristine conditions has a high variety of species or "taxa". In general, high taxa richness is considered good, although mildly impacted (nutrient-enriched) rivers can have higher taxa richness than pristine streams and rivers.

Percentage of EPT taxa

The invertebrate community is usually dominated by three orders of insects: the mayflies, stoneflies, and caddis flies. Together, these insects are known as EPT, referring to their scientific names Ephemeroptera, Plecoptera and Trichoptera, respectively. These freshwater insects are generally intolerant of pollution, so the fewer found in a sample, the poorer the stream health.

The percentage of EPT-taxa (or %EPT) is most commonly calculated by counting the total number of mayfly, stonefly and caddis fly taxa in a sample, then dividing that number by the taxa richness and multiplying by 100. This is known as the %EPT by taxa.

A high percentage of EPT taxa indicates good stream health. However, in some New Zealand streams there are naturally few mayflies, stoneflies, or caddis flies present. Ecologists need to be aware of these factors when using the %EPT to assess the ecological health of a river or stream.

Macroinvertebrate Community Index (MCI)

The MCI is based on the tolerance or sensitivity of species (taxa) to organic pollution and nutrient enrichment. For example, mayflies, stoneflies and caddis flies are sensitive to pollution, and are only abundant in clean and healthy streams, whereas worms and snails are more tolerant and can be found in polluted streams. Most benthic invertebrate taxa were assigned a tolerance value ranging from 1 (very tolerant) to 10 (very sensitive).

An invertebrate sample is typically collected from within a small section of a stream (a reach). Higher MCI scores indicate better stream conditions at the sampled site. In theory MCI values can range between 0 and 200, but in practice it is rare to find MCI values greater than 150 and only extremely polluted or sandy/muddy sites score under 50.

The MCI for a stream site is based on the presence (or absence) of invertebrates. There are different sampling methods that can be used to sample for macroinvertebrates in streams, such as kick-netting of Surber sampling methods, depending on how much information is required.

Important to know

The MCI is designed specifically for stony riffle substrates in flowing water. This means that when interpreting scores some knowledge is needed of the types of instream habitat where the invertebrate samples were collected. For example, some streams in New Zealand naturally do not have high-scoring taxa such as mayflies, stoneflies or caddis flies, which may be due to the geology, climate, flow regime or a natural absence of riverbank vegetation. These streams may have a MCI score indicating "poor" quality (i.e. less than 80), but may not in fact be degraded. To help overcome this problem a set of different tolerance values have been developed to be used for sites with naturally silty, soft-bottom substrates. Ecologists need to be aware of these factors when using the MCI to assess the ecological health of a river or stream.

MCI grading guidelines

In the table below are the grading guidelines for MCI that are used to describe the health of a stream or river:

Quality class

Description

MCI score

Stream in excellent ecological condition. Indicative of excellent water quality and/or habitat conditions.

>119

Stream in good ecological condition. Indicative of good water quality and/o r habitat conditions.

100 - 119

Stream in fair ecological condition. Indicative of only fair water quality and/or habitat conditions.

80 - 99

Stream in poor ecological condition. Indicative of poor water quality and/or poor habitat conditions.

<80

How do I sample benthic macroinvertebrates?

Two common methodologies for sampling macroinvertebrates are kick-netting (sometimes called hand-netting) and Surber sampling (see examples of sampling equipment for each of these techniques below). Which method to use depends on the reason for collecting the samples.

Example of a kick-net (left) and a Surber sampler (right).
Kick-nets are generally used when you want to know about the diversity of invertebrates or the general ecological health of a stream or river. Kick-netting is a semi-qualitative sampling technique, where the sample is not collected from a defined area of streambed.

A Surber sampler is used when you want to know the number of invertebrates in a defined area of streambed, for example per square metre. This is important if you want to understand how productive a stream or river is.

What else needs to be considered when sampling for benthic macroinvertebrates?

Timing

In New Zealand, the presence or absence or the amount of different invertebrate groups does not generally vary between seasons, so communities can be sampled at any time of the year for use of stream health indices such as EPT taxa richness and the MCI. However, to effectively compare sites and consider long-term trends, it is important to sample during the same season each year (typically summer) as other environmental influences on invertebrate communities can affect the presence and number of animals. For example, the amount of freshwater algae can affect the kind of aquatic invertebrates that make up a macroinvertebrate community and river flows such as floods can wash animals out, reducing the numbers found. Invertebrates are generally not sampled within 2 - 3 weeks following a large flood to allow the macroinvertebrate communities time to recover.

Habitat considerations

The diversity and density of invertebrates can vary a lot within a stream. For example, there will be a greater variety and number of invertebrates in shallow, swift riffles than in deep, slow-flowing pools; and invertebrates that inhabit the slower flowing margins of a steam may be different to those in swifter areas. It is therefore important to give thought to where in the stream invertebrates are being collected from.

Where do I find more information?

Chapman, Lewis and Winterbourn 2011. Guide to freshwater crustacea of New Zealand.

Stark JD 1985. A macroinvertebrate community index of water quality for stony streams. Prepared for National Water and Soil Conservation Authority. Water & Soil miscellaneous publication. 53p. p.

Stark JD, Boothroyd IKG, Harding JS, Maxted JR, Scarsbrook MR 2001. Protocols for sampling macroinvertebrates in wadeable streams. 1-57 p.

Stark JD, Maxted, JR 2007. A user guide for the Macroinvertebrate Community Index. Prepared for the Ministry for the Environment. Cawthron Report No. 1166. 58

Winterbourn, MJ, Gregson, KLD and Dolphin, CH 2006. Guide to the aquatic insects of New Zealand.

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Benthic invertebrate communities are widely used as indicators of stream ecosystem health because they include a wide range of species, each with relatively well-known sensitivity or tolerance to stream conditions. The most common stream health indices are taxa richness, percentage of EPT taxa and the macroinvertebrate community index (MCI).

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A brief look at stoneflies. Stoneflies are found around the world, and while NZ has its own species, they have many similarities.

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This is not a NZ species but the same cycle applies.

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This is not a NZ species, but the same cycle applies.

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Not an NZ species but the life cycle is the same.

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Investigate adaptations to living in freshwater

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Investigate adaptations to living in freshwater