Insects Key Indicators of Water Health, Experts Say

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They eat algae and other organic matter and in turn are food for fish and birds (related news: "Insects Key to Rain Forest Diversity, Study Shows" [March 10, 2005]).

"Different invertebrates may live from months to years, so the types present reflect what has happened in a stream over that span of time."

When Herbst inspects a stream, he looks for things like insect diversity and size.

He asks, Do only hardy, tolerant insects thrive in the water or are there ecologically sensitive insects too? Does the stream contain only insects that eat algae or also insects that prey on other insects—an indication of a healthier ecosystem?

All the details, he said, provide more information than the snapshots of a single time and place gleaned from water quality tests.

EPA's Mayer said information from standard water-quality tests is helpful for monitoring contaminant levels for people.

"But the question is, Is that clean enough for the health of the ecosystem?" he said.

"The critters living in these mountain stream ecosystems can be extraordinarily sensitive to small changes in chemistry."

Standard Setting

Herbst tries to answer this question by developing reference standards, which are compiled from studies of streams within watersheds that have experienced little human impact.

The standards become benchmarks for projects such as the mine cleanup.

Herbst then studies the insect community after each cleanup project Mayer and his team implement.

In one case, he found that insect diversity improved after the cleanup team built ponds to capture summertime runoff from snowmelt and rain. Neutralizing chemicals added to the ponds strip pollutants from the water, creating cleaner runoff.

Diversity also improved after construction of a rocky wetland full of bacteria that reduce the acidity of the mine's sulfuric waters. Contaminated waters enter the wetland at one end and come out clean on the other side.

"That project resulted in a huge improvement in the condition of one stream over a single summer," Herbst said.

"We would not have known the ecological success had we not been monitoring before and after."

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