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Viola
According to the Hilsenhoff Biotic Index, the water quality in both these sites is very, very poor!

Gray
Wait a minute—what index is this?

Beadle
The Hilsenhoff Biotic Index, or HBI, measures the health of a stream on a scale from 1 to 10. A value of 1 suggests the presence of a macroinvertebrate community that is very sensitive to pollution, meaning that the water quality is excellent. A value of 10 suggests the opposite. Let me have a look at your data, Ms. DeRama.

Viola
I’m shocked, absolutely shocked that such a polluted stream is flowing unchecked through Yellowstone National Park! It’s enough to make me speechless!

Maya
I wish!


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Cast of characters - Maya Crowbes, Dr. A Beadle, Gray Fischer, Viola DeRama
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Q: What is measured by the Hilsenhoff Biotic Index?

GLOSSARY: Hilsenhoff Biotic Index (HBI)—a measure of the health of a stream on a scale of 1-10 (with 1 being most healthy) that is based on the macroinvertebrate communities present

ACTIVITY 1: Drag Net! (1KB pdf)