| Benthic Macro-invertebrates |
Bottom dwellers Easily visible (not microscopic) Lacking a backbone: insect larvae, worms, etc.
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Benthic macro-invertebrates represent a significant biomass in healthy streams and play an important role in the food chain. Some shred organic matter and are preyed upon by other benthics. Most serve as a food source for fish and salamanders. Adult insects hatched from aquatic larvae provide prey for frogs, toads, bats, and many birds.
The mix of species changes with the quality of stream habitat. Research scientists studying this relationship have devised an Index of Biotic Integrity based on the mix of species.
Flies and midges | Mayflies, Stoneflies, Caddisflies |
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More tolerant Greater proportion of more-tolerant organisms indicates poorer habitat conditions. | Less tolerant Greater proportion of less-tolerant organisms indicates better habitat conditions. |