Aquatic Macroinvertebrates (water bugs) are widely used as an indicator of stream health.  Through the Earth Stewardship Program students sample for Macroinvertebrates and classify them based on their tolerance or intolerance for pollution. Some families of macroinvertebrates such as Stoneflies, Caddisflies, and Mayflies are especially sensitive to pollutants and are commonly used as bio-indicators.

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The diversity of Macroinvertebrate taxa where used to determine if nonpoint source pollution is an issue on two sites in the Bitterroot Watershed.

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Nonpoint source pollution is caused when precipitation carries pollutants from the ground into water bodies.  These pollutants are typically sediment and nutrients like nitrogen and phosphorus.  Temperature issues are often also attributed to nonpoint source pollution.