Nonfiction Sample
How much can a poor insect take? In the watery micro-worlds of "riffle communities" in Wisconsin streams and rivers, researchers can now quantify how much organic pollution an insect can take. Biologists use this information to rate the health of waterways according to the organic pollution tolerance levels of the riffle organisms that live there.

The key to this process is the "biotic index," an index specifically devoted to Wisconsin's aquatic insects and crustaceans. The biotic index (B.I.) rates species' organic pollution tolerance levels on a scale of 0 to 10, with 0 the lowest tolerance and 10 the highest. When individual organisms collected from a stream site are sorted on the B.I. scale, the relative distribution of tolerance levels gives a rough indication of the stream's organic pollution level.

Excerpt from "Insects Reveal Clues to Water Quality," Natural Resources Report (UW-Madison, 1991).

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