What Are the Bugs Telling Us?

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Macroinvertebrate sampling to assess stream health

Macroinvertebrate sampling to assess stream health

If you live in the Clackamas River watershed, you may have noticed folks in orange vests looking under rocks and kicking the sediment in Doane and North Fork Deep creeks in early October. The Clackamas County Soil and Water Conservation District hired them to collect data on macroinvertebrates.

Macroinvertebrates are organisms without a backbone that are large enough to be seen with the unaided eye. They live in a waterbody or stream for an extended period of time, are sensitive to habitat loss, chemical pollution, and excessive sediment in the water. This makes them good indicators of overall stream health.

The streams in this story may not be the ones in your neighborhood, but macroinvertebrates live in all waterbodies. Do you know what is going on in your area creeks?

What kind of bugs are in the stream?

Macroinvertebrates can be divided into three groups. The first group is sensitive to warm water temperatures and acidity. This group needs high levels of oxygen in the water. This group includes mayfly, caddisfly, and stoneflies.

The second group is more tolerant of pollutants in the water. They include dragonfly, damselfly and scuds.

The third group is tolerant of polluted water that is warm, may have too much sediment in the water, too high or low acidity, and not enough oxygen. This group includes aquatic worms and midge larvae.

What did we find?

With the exception of our reference site on Tickle Creek near Sandy, the stream sites sampled in this “watershed check-up” support macroinvertebrate species able to tolerate degraded conditions. Very few sensitive macroinvertebrates (mayfly, caddisfly, and stoneflies) were found. We did find species able to tolerate elevated sediment loads and increased water temperatures.

The index used to score the macroinvertebrate community conditions show all sites were severely disturbed, except Tickle Creek that was rated slightly disturbed. Our consultant concluded that elevated water temperature and sediment load were problems at all sites.

What can you do?

Macroinvertebrate communities recover fairly quickly when their habitat conditions improve. This is one reason they are a good indicator of stream health. If sediment loads and warm stream temperatures are harming bugs in the stream, keeping soil out of the stream and shading the stream are things that will improve stream health.

The most economical and easiest restoration actions you can take are planting trees, shrubs, and grasses in the streamside area. Native vegetation provides many benefits including sediment and pollutant filtration, shading, insect food sources, bank stability, and eventually large wood for the stream. Other beneficial actions include erosion control practices on fields and barnyards.

Read the technical report

Linked below is the report, downloadable as a PDF file.

We’re available to help

We can help you control erosion on your property and create a beautiful shaded streamside. Our assistance is free and we often have financial programs to help.

Call the Conservation District at (503) 210-6000 to find out more. In the Clackamas River watershed, you can also contact the Clackamas River Basin Council at (503) 303-4372 for riparian planting assistance.

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