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Airdate: Jun 14, 2001
Scientist: Dave Herbst

Bugs in the Water - Living Barometer

Bugs in the Water - Living Barometer
Populations shifts of different organisms within the same stream bed can indicate changes in water quality.


ambience: water lapping

Insects living in a stream can be a kind of barometer for the condition of a local habitat. I’m Jim Metzner and this is Pulse of the Planet. By looking at the kinds of bugs present in a stream, Dave Herbst of the Sierra Nevada Aquatic Research Lab, can tell you a lot about the quality of the water.

“Okay, so what I’m doing is rolling around rocks on the stream bottom and rubbing the surface of the rocks with my hands to dislodge any organisms that might be attached to the surfaces of those rocks, and so what I’m trying to do is also sample sort of a cross section of the different kinds of habitats that are on the stream bottom here - sampling off boulders, cobbles, gravel, sandy sediments - the different kinds of organisms that are in the stream, inhabit preferentially those different kinds of micro habitats. So let’s put these bugs in the bucket, and see what we’ve got. With these stone flies here, these big predatory stone flies, first of all, they’re big. And that means that they have to have sufficient habitat that they can crawl in between the interstices of cobbles and boulders in the stream. Too much sediment removes the habitat between rocks, and these guys can’t survive. They only like to live at low temperatures, clean water, high oxygenation, good current velocity. Outside of those kinds of circumstances they disappear, so they’re a very sensitive organism. And so they’re useful in interpreting the water quality, and habitat quality conditions at a particular site. They’re another indicator of a favorable environment for their survival and good habitat."

Every part of a stream may host a different assortment of bugs, with each species giving distinct information about the state of the stream. Over time, Dave Herbst logs how the bug populations and the stream habitat have changed.

Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation. I’m Jim Metzner.