Stream Critters Reveal Much About Water Quality

by Micka Peck

I was never a huge ‘bug person’ as a kid. It wasn’t that I bolted in terror at the sight of anything crawling my direction, but I didn’t greet a dangling spider with much enthusiasm either. My little brother, on the other hand, loved running through fields of tall grass in search of massive grasshoppers and butterflies. So, it may have come as a surprise to my family when a colleague and I eagerly set off to West Virginia in search of benthic macroinvertebrates, or the bottom-dwelling stream critters that lack backbones and are visible to the naked eye. Think insects, crayfish, worms, mussels, etc.

A couple of things piqued my interest about these creatures. I had learned that benthic macroinvertebrates are a crucial indicator for understanding water quality. While a single “grab sample” from a stream can tell you something about its water quality at that moment, macroinvertebrates are exposed to a range of conditions throughout their life stages in water. Therefore, they more accurately represent long-term conditions of water quality. Some macroinvertebrates are very sensitive to pollutants and as the water quality worsens, are less prevalent. All of our Region 3 states rely on macroinvertebrates to assess whether a waterbody is supporting aquatic life, so I thought I should go see what all the fuss was about.

We arrived at the stream bank in waders toting buckets, scrub brushes, and a large net. After surveying the stream, we chose a few spots with fast moving water and a variety of rocks and cobble, which are popular habitats due to their shelter from predators. With the net placed on the streambed facing upstream, I grabbed the scrub brush, brushed the rocks and let any attached macroinvertebrates float into the net. Next, I kicked the rocks in front of the net to stir up any macroinvertebrates hiding underneath and let the water guide them into the net. At times, it looked like I was dancing the twist in the middle of the stream. Then, I dumped the contents in the net into a bucket and marveled at the bounty. It was teeming with crayfish, scuds, larvae of mayflies, stoneflies, dragonflies, and so much more. And now, rather than feeling ambivalent, I’m filled with a sense of childish wonder at the many surprises a stream may hold.

Stay tuned for Part 2 – in the lab!


About the Author: Micka Peck is a physical scientist in EPA’s Mid-Atlantic Region working on improving impaired waters through total maximum daily loads (TMDLs), or water quality improvement plans.


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