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Benthic Macroinvertebrates
Benthic macroinvertebrates are bottom-dwelling aquatic organisms without backbones. They are useful indicators of stream health because they are abundant, diverse, sedentary, and reflect cumulative environmental impacts. Various metrics related to the types of macroinvertebrates present are used to calculate a Benthic Index of Biological Integrity (B-IBI) score that indicates the overall biological condition of a stream. A higher B-IBI score, with more diverse and pollution-intolerant taxa, corresponds to better stream health.
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Benthic Macroinvertebrates
- 1. Extreme BenthicsExtreme Benthics AcademyAcademy ““BenthicMacroinvertebrates 101”Benthic Macroinvertebrates 101”
- 2. What are BenthicWhatare Benthic Macroinvertebrates?Macroinvertebrates? Benthic = bottom dwellingBenthic = bottom dwelling Macro = large enough to see with the naked eyeMacro = large enough to see with the naked eye Invertebrate = without a backbone (could be a clam, a worm, aInvertebrate = without a backbone (could be a clam, a worm, a crab, or an insect, for example)crab, or an insect, for example) Often refer to them as “stream bugs”
- 3. Big Diversity ofBenthicBig Diversity of Benthic MacroinvertebratesMacroinvertebrates Leech Black fly larva Midge Dragonfly Crawdad Cranefly Mosquito Caddisfly Mayfly Stonefly Gilled snail
- 4. Why Do WeMonitorWhy Do We Monitor Stream Bugs?Stream Bugs? Chemical WQ data offers good, but limitedChemical WQ data offers good, but limited information.information. Only a “snapshot” view of conditionsOnly a “snapshot” view of conditions Doesn’t measure “biology”Doesn’t measure “biology” Nitrates pH D.O. Fecal coliform Temperature T.S.S
- 5. BiologicalBiological AssessmentAssessment Use livingorganisms to tell us somethingUse living organisms to tell us something about the environmentabout the environment
- 6. Why Use “streambugs” inWhy Use “stream bugs” in Bioassessment of StreamsBioassessment of Streams AbundantAbundant DiverseDiverse SedentarySedentary
- 7. Stream Bugs =excellent indicatorStream Bugs = excellent indicator of the stream’sof the stream’s biologicalbiological health.health. Populations reflectPopulations reflect cumulativecumulative impacts .impacts . They are easy to sample.They are easy to sample. They have the same habitat needs as salmon .They have the same habitat needs as salmon .
- 8. Habitat Needs forSalmon andHabitat Needs for Salmon and Stream Bugs:Stream Bugs: Clean, cold, oxygenated waterClean, cold, oxygenated water Connected migration pathsConnected migration paths HabitatHabitat features for spawning andfeatures for spawning and rearingrearing DependableDependable stream flowsstream flows
- 9. Habitat Features forSpawning andHabitat Features for Spawning and RearingRearing
- 10. Dependable Stream FlowDependableStream Flow
- 11. High FlowsHigh Flows SmotheredSalmon Eggs
- 12. Stream BugsStream Bugs TellA StoryTell A Story No “good” or “bad” bugsNo “good” or “bad” bugs Presence or absence indicates healthPresence or absence indicates health Diversity (not total number of bugs) = HealthierDiversity (not total number of bugs) = Healthier samplesample
- 13. How Do TheyTell The Story?How Do They Tell The Story? B.I.B.I.B.I.B.I. ““Benthic Index of Biological Integrity”Benthic Index of Biological Integrity” 10 “metrics” indicating stream health10 “metrics” indicating stream health
- 14. 10 Metrics10 Metrics Taxa richnessTaxa richness # mayfly taxa (Ephemeroptera)# mayfly taxa (Ephemeroptera) # stonefly taxa (Plecoptera)# stonefly taxa (Plecoptera) # caddisfly taxa (Trichoptera)# caddisfly taxa (Trichoptera) # long-lived taxa# long-lived taxa # intolerant taxa# intolerant taxa % tolerant taxa% tolerant taxa % predators% predators # clinger taxa# clinger taxa % dominance (3 taxa)% dominance (3 taxa) Mayfly larva Stonefly larva Caddisfly larva Caddisfly case
- 15. Taxa RichnessTaxa Richness Leech Blackfly larva Midge Dragonfly Crawdad Cranefly Mosquito Caddisfly Mayfly Stonefly Gilled snail
- 16. % Dominance (3taxa)% Dominance (3 taxa) Ephemeroptera Plecoptera Trichoptera leech bloodworm netspinner caddisfly Intolerant species Tolerant species Plecoptera
- 17. Number of IntolerantTaxaNumber of Intolerant Taxa lepidostomatidae caddisfly ephemerellidae mayfly nymph capniidae stonefly nymph Gilled snailDobsonfly larva Riffle beetle Water penny
- 18. % Tolerant Taxa%Tolerant Taxa leech black fly larva bloodworm netspinner caddisfly baetidae mayflies Midge larva
- 19. Number of ClingerTaxaNumber of Clinger Taxa Water penny Stonefly nymph Mayfly nymph Caddisfly larvae – Caddisfly Alderfly Riffle beetle larva
- 20. Number of Long-LivedTaxaNumber of Long-Lived Taxa Dragonfly nymph Alderfly larva Gilled snail Pteronarcys stonefly Dragonfly nymph
- 21. Number of MayflyTaxaNumber of Mayfly Taxa (Ephemeroptera)(Ephemeroptera)
- 22. Number of CaddisflyTaxaNumber of Caddisfly Taxa (Trichoptera)(Trichoptera)
- 23. Number of StoneflyTaxaNumber of Stonefly Taxa (Plecoptera)(Plecoptera)
- 24. % Predators taxa%Predators taxa water beetle Dragonfly larva Great diving beetle Stonefly larva Rhycophila caddisfly
- 25. Computing the B.I.B.I.Computingthe B.I.B.I. Example: Taxa RichnessExample: Taxa Richness 0-20 taxa = low (0-20 taxa = low (11)) 21-40 taxa = moderate (21-40 taxa = moderate (33)) 40+ taxa = high (40+ taxa = high (55))
- 26. Computing the B.I.B.I.Computingthe B.I.B.I. Taxa richnessTaxa richness 11 33 55 # mayfly taxa (Ephemeroptera)# mayfly taxa (Ephemeroptera) 1 31 3 55 # stonefly taxa (Plecoptera)# stonefly taxa (Plecoptera) 11 33 55 # caddisfly taxa (Trichoptera)# caddisfly taxa (Trichoptera) 11 3 53 5 # long-lived taxa# long-lived taxa 11 3 53 5 # intolerant taxa# intolerant taxa 11 33 55 % tolerant taxa% tolerant taxa 11 3 53 5 % predators% predators 11 33 55 # clinger taxa# clinger taxa 1 31 3 55 % dominance (3 taxa)% dominance (3 taxa) 1 31 3 55
- 27. Computing the B.I.B.I.Computingthe B.I.B.I. Taxa richnessTaxa richness 33 # mayfly taxa (Ephemeroptera)# mayfly taxa (Ephemeroptera) 55 # stonefly taxa (Plecoptera)# stonefly taxa (Plecoptera) 33 # caddisfly taxa (Trichoptera)# caddisfly taxa (Trichoptera) 11 # long-lived taxa# long-lived taxa 11 # intolerant taxa# intolerant taxa 33 % tolerant taxa% tolerant taxa 11 % predators% predators 33 # clinger taxa# clinger taxa 55 % dominance (3 taxa)% dominance (3 taxa) 55 TOTAL:TOTAL: 3030
- 28. Final B.I.B.I. Scores*FinalB.I.B.I. Scores* 10 – 16 = Very Poor10 – 16 = Very Poor 18 - 26 = Poor18 - 26 = Poor 28 – 36 = Fair28 – 36 = Fair 38 – 44 = Good38 – 44 = Good 46 - 50 = Excellent46 - 50 = Excellent *10 Metric B-IBI Score used by Mindy Allen*10 Metric B-IBI Score used by Mindy Allen Stonefly Caddisfly
- 29. When in theField….When in the Field…. Observe: land use, canopy cover…etc.
Editor's Notes
- #4 There is a large diversity of benthic macroinvertebrates that may live in fresh water streams….insects, worms, snails, crayfish, spiders, and leeches
- #5 For decades we have been monitoring for “chemical” water quality parameters: dissolved oxygen, nitrates, pH, fecal coliform, total suspended solids, temperature….to see if our streams are healthy. But, sometimes chemical monitoring indicates good water quality, when, in fact, the stream is not “biologically” healthy (i.e. doesn’t support a diversity of aquatic life). This is because chemical WQ monitoring only occurs maybe 4X a year…a snapshot….and may miss major events like an oil spill or a time when the stream goes dry in the summer. Also, chemical testing is just that…..it assesses the chemistry, not the biological health , or the status of living things in the water.
- #6 How do we assess the biological health of a stream? Conducting a biological assessment….using living organisms….
- #7 Why use stream bugs and not fish or frogs? Abundant: 100s or thousands of them can live in one square meter of substrate. A large sample population can be collected in minutes using inexpensive equipment. Diverse: 100s of species live in a single stream. One intensely studied stream in South Carolina reported more than 1,000 species were found. Diversity and abundance are indicators of water quality and environmental health (describe in more detail later). Sedentary: generally stay in one place in the stream for much of their aquatic life phase. Some have body parts adapted to hold onto gravel in strong currents, others attach their shelters to the stream bottom and live inside them. Easier to catch than frogs and fish. More importantly, they are exposed to stream conditions in one place over a long period of times (weeks, months or years)
- #8 Stream bugs are an excellent indicator of a stream’s biological health. The composition of stream bug populations reflects cumulative impacts, or everything that’s happening in the stream and on the land draining to the stream all year long. So, all the activities of humans and animals in the stream basin (leaky cars, pooping dogs, acres of pavement, drained wetlands) have an impact on the stream and the critters living in it. You could take a chemical WQ sample in Percival Creek at Trosper Road, on a cold, calm winter day, and the data might indicate acceptable levels of DO and TSS, but a macro sample would indicate poor biological health. Why? In the summer, the stream will be too warm. Large runoff events in the past have silted in the gravels. Runoff from Trosper Road may carry oil and other pollutants. Stream bugs have similar habitat needs as salmon and are easier to sample than salmon. Electroshocking and scuba diving have their limits, and bugs don’t swim away The loss of biological integrity within salmon spawning grounds equates to a loss of salmon. If a stream's biological condition is degraded (as reflected by the condition of the benthic macroinvertebrate population), it is safe to conclude that the stream will not support healthy salmon or other fish populations. The decline of healthy salmon spawning and rearing habitat has been identified as one major cause of the decline of wild salmon populations.
- #9 For Pacific Northwest streams, what do aquatic organisms such as salmon and macroinvertebrates need to survive?
- #10 Aquatic organisms need a variety of structures within the stream and along the banks to provide the right kinds of habitats. Logs, root wads, and boulders in a stream create pools for resting and broken, ripply water (riffles) for capturing oxygen. Clean gravel and larger cobbles are needed for aquatic insects to cling to and for salmon to spawn in. Trees along the banks prevent erosion and provide overhanging vegetation for protecting young fish from predators. When trees into the stream, they provide more hiding places.
- #11 The amount of water in a stream is determined largely by how the land draining to the stream (the watershed) has (or hasn’t) been developed. In an urbanized watershed, stream flows fluctuate greatly (high flows during winter storms and low flows –or no flows-in the summers) as compared to a forested watershed.
- #12 Repeated high winter flows scour streambanks, wash away logs and gravels, and smother salmon eggs with sediments. Water quantity is a greater problem in many watersheds than water quality.
- #13 How do benthic macroinvertebrates tell a story about water quality? How can they be used in bioassessment? Even stream bugs that are more tolerant to low DO levels or pollution have a place in healthy stream ecosystems. Type of bug can tell us something about the stream: i.e. Diving beetles = low DO; some snails = little canopy; long-lived stoneflies = minimal bad impacts to stream Range of tolerances are specific for each species. Some may be sensitive to pollution while others may not be. Presence or absence and relative abundance often indicative of how good or bad the habitat is. 3. When environmental conditions decline, the intolerant species are the first to disappear, which leaves a niche open for more tolerant organisms to fill.
- #14 (1) B.I.B.I. Stands for Benthic Index of Biological Integrity. (2) Just as the “cost of living” index is computed by compiling a number of indicators like the price of housing and the price of groceries, the Benthic index is computed by compiling 10 measurements (metrics) of stream health related to the “bug” community. (3) The 10 metrics were developed by comparing the “bug” species in pristine streams, to streams in urban settings that are highly influenced by human activities.
- #15 We might measure human health by measuring blood pressure, temperature, white cell count, etc., each measurement targeting a different aspect of the body’s health system. Similarly, these 10 metrics are used to measure the biological health of a stream. The word “taxa” means a group, or category; most often, with bug I.D., taxa refers to species.) Each metric looks at a different aspect of the stream’s health. For example…. the metric, “% predators”, would tell you what percent of your sample consists of predator organisms…bugs that are at the top of the macro food chain and therefore indicative of a complex and diverse ecosystem.
- #16 The first one is Taxa Richness. As with any ecosystem, a great diversity of organisms in a stream indicates excellent health. This is called “Taxa Richness.” The more different kinds of “bugs” (different taxa), the healthier the stream. Shown here are a variety of bugs, most in their larval stage: We see a leech, stonefly, dragonfly …etc. Leeches and mosquito larvae are often considered indicators of polluted streams, however, they can be present in healthy streams as well. If they were the dominant organisms, with the stream having little diversity, that would indicate a problem. Such situations have earned leeches and mosquito larvae the reputation of “bad bugs”, but thinking in terms of “good bugs” and “bad bugs” is faulty thinking. In a healthy stream, there are niches for all kinds of organisms.
- #17 As diversity declines, a few taxa will dominate. Opportunistic species that are less particular about where they live will replace species that have specific food, habitat or oxygen requirements. A low score of “1” would mean that the three most abundant taxa are dominating the population, and, therefore the system is out of its natural balance. (Somethin is driving the other species out.)
- #18 These taxa are particularly intolerant to nutrient pollution, such as fertilizer and sewage) and of low levels of DO. They are the first to disappear as human disturbance increases. Species intolerant to sewage pollution = ephemerellidae mayfly, LEPIDOSTOMATIDAE caddisfly, capniidae stonefly, for example.
- #19 These taxa can tolerate higher levels of nutrient pollution and lower levels of DO. They will be present at most stream sites, but when they begin to dominate (their % increase), that usually indicates a problem. A low score of “1” means that these taxa represent a high percentage of the population. Another metric measures the per cent of bugs in a sample which are tolerant to pollution such as sewage. Seen here: Species tolerant to sewage = leeches, black fly larva, netspinner caddisflies, bloodworms, baetidae mayflies.
- #20 Another metric, “cllinger” taxa, measures the variety of critters that cling to rocks in a stream. When a stream becomes too loaded with sediment, and gravels are silted in, these bugs cannot survive. Examples of clinger species: riffle beetle larva, water penny, alderfly, many kinds of stoneflies, mayflies, and caddisflies
- #21 The metric, “long-lived taxa”, would tell you how many different kinds of bugs in your sample live longer than one year in the larval stage, thereby indicating that nothing bad has happened (like the stream going dry) in the last year. Examples include: many dragonfly nymphs, a number of molluscs, pteronarcys stoneflies, and alderflies
- #22 Three of the metrics measure the diversity, or taxa richness, of “ephemeroptera” (mayflies), “pleicoptera” (stoneflies), and “tricoptera” (caddisflies). (Sometimes referred to as “EPT richness”.) These three groups are particularly good indicators of stream health. Many of these bugs breathe through gills and are the first to disappear when stream conditions are degraded such as when too much sediment is in a stream. So, the more EPT taxa present,(the more different kinds of mayflies, stoneflies, and caddisflies), the healthier the stream. Many mayflies graze on algae and are sensitive to chemical pollution and heavy metal concentrations that interfere with their food source. Mayflies cannot tolerate low DO levels. Breathe through gills
- #23 Since the ways in which caddisflies breathe and find food are varied, it is difficult to pinpoint any one cause of their decline. However, taxa richness definitely declines as human impacts increase and the complexity of the stream’s habitat is reduced.
- #24 Many stoneflies are predators, hide among gravel. Low diversity of stonefly may be due to sedimentatioin or lack of a cobble substrate. Stoneflies need a high level of dissolved oxygen. Breath through gills.
- #25 Represent peak of food web and depend on a reliable food source of other invertebrates that they can eat. The higher the % of predators, the healthier and more complex the ecosystem is. The lower the % predators, the more degraded is the stream. *Predators also need hiding spaces between cobble.
- #26 Each of the 10 metrics gets a score of “1”, “3”, or “5”, depending on whether the bugs present in the sample represent a low, medium, or high level of stream health. For example, if we look at the metric, “taxa richness”, we see that a sample with 20 different kinds of bugs or less would be considered low, and receive a score of “1”. If a sample had over 40 different kinds of bugs, it would get a “5”.
- #27 The B.I.B.I. Is calculated by adding up all the 1’s, 3’s, and 5’s for each of the 10 metrics. The lowest score of biological integrity would be 1 X 10 = 10. The highest score would be 5 X 10 + 50. In this example, the score adds up to 30.
- #28 The B.I.B.I. Is calculated by adding up all the 1’s, 3’s, and 5’s for each of the 10 metrics. The lowest score of biological integrity would be 1 X 10 = 10. The highest score would be 5 X 10 + 50. In this example, the score adds up to 30.
- #29 Based on comparing the bug populations of pristine streams with degraded streams, B.I.B.I. Scores are rated as Very poor, Poor, Fair, Good and Excellent. A score of 30 would indicate Fair biological health. It is important to not only look at the final B-IBI score, but to look at the individual metric scores for clues to the types of impacts affecting the final score. For example: Did you have a high percentage of pollution tolerant taxa? Were long lived taxa present? Were sediment tolerant taxa present? The individual metrics, the original data set, and your notes on the land uses surrounding the site will help you understand the processes occurring within and around your sampling site. Indices of Biological Integrity do more than generate a final score - they provide the opportunity to investigate the types of influences acting upon a watershed. However, keep in mind that human disturbances act upon stream systems in complex ways and thus the resulting IBI scores should be interpreted as a whole (Rossano, 1996). For example, a sampling site may possess high diversity (i.e., total taxa richness) and thus indicate a high biological integrity score. However, if the species contributing to a high diversity are pollution tolerant species, the overall biological integrity of the system may be poor. Knowing the stream ecology of the different taxa associated with streams in your region will aid in the interpretation of your data and the resulting IBI.
- #30 Most of you will attend the Student Green Congress in the spring. You will have time during the Congress to analyze your data and discuss what things may be impacting the health of your stream. So, it is important that you take notes about land use activities near your site, canopy cover…