6.1 Biological indicators of stream health
Examining the organisms inhabiting a stream provides valuable information about stream health. Macroinvertebrates (small animals without backbones) are often used to assess stream health. When a large number of different macroinvertebrates inhabit a stream or when those macroinvertebrates that inhabit a stream are particularly pollution-intolerant or oxygen-demanding, the stream is generally considered to be healthy.
In the field, scientists use various collection techniques to capture stream macroinvertebrates. They then identify the macroinvertebrates using dichotomous keys and calculate various metrics to assess stream water quality.
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