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Watershed Watch Community Science

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What is an Benthic Macroinvertebrate, How to Sample, What do they tell us about Watershed Health?

July 23, 2020

The word “benthic” means bottom dwelling and refers to organisms that live on
the bottom (substrate) of a river, stream or lake. The term “macroinvertebrate”
means the organisms without a spine (invertebrate) that can be seen without the
aid of a microscope or can be seen by the unaided eye.

Aquatic insects are excellent long-term indicators of stream and watershed
health. Because the insects must live in the river all year long, they integrate
the results of the impacts of overall water quality conditions. For example,
watersheds with historic and current overgrazing or urban areas with over 25%
of impervious surface tend to have benthic communities that are less diverse
and more dominated by pollution-tolerant insects than watersheds that are less
disturbed by human communities (May 2000). Benthic insects tell a story
about the direct impacts of a variety of stressors and their cumulative effects.