Bugs as Indicators of Water Quality

Got bugs?

Macroinvertebrate sampling to assess stream health

Did you notice folks in orange vests looking under rocks and kicking the sediment in Doane and North Fork Deep Creeks in early October? They were staff and volunteers from Clackamas Soil and Water Conservation District braving the cold water 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. They are sensitive to habitat loss, chemical pollution, and excessive sediment in the water. These responses to water quality make them good indicators of overall stream health.

Clackamas Soil and Water Conservation District is part of a group of organizations and agencies that conduct macroinvertebrate sampling as part of a long-term assessment of water quality. Each group has established sites that they monitor periodically. By coordinating these efforts, a larger picture of Clackamas River watershed health is emerging. The District conducted an earlier sampling event in October 2012.

What kind of macroinvertebrates are in the stream?

Macroinvertebrates belong in three groups.

  1. 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.
  2. The second group is more tolerant of pollutants in the water. They include dragonfly, damselfly and scuds.
  3. 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?

Mayflies are indicators of good water quality

The results from 2016 did not differ much from what we found in 2012.

Our reference site on Tickle Creek near Sandy supported the largest variety of macroinvertebrate species. This site is classified as only slightly impaired to moderately disturbed, depending on the index used.

The other sites only had macroinvertebrate species that are 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 rate all sites as severely disturbed, except the Tickle Creek site that was rated slightly disturbed. Our consultant concluded that elevated water temperature and sediment load were problems at all sites.

What can you do?

Recovery of the macroinvertebrate community depends on improving stream conditions. 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.

Download and read the full reports

You can read the two reports from 2012 and 2016. Get them here:

2012 Stream Benthic Macroinvertebrate Assessment
2012 Stream Benthic Macroinvertebrate Assessment
ABR_Clackamas_SWCD_Macroinvertebrate_Study_2012.pdf
2.2 MB
52 Downloads
Details...
2016 Stream Benthic Macroinvertebrate Assessment
2016 Stream Benthic Macroinvertebrate Assessment
16-127_ClackSWCD_Macros_FINAL_Rpt_12-10-16.pdf
Version: 2016
2.8 MB
22 Downloads
Details...
2018 Stream Benthic Macroinvertebrate Assessment
2018 Stream Benthic Macroinvertebrate Assessment
18-127_ClackSWCD_Macros_FINAL_Rpt_2-4-19.pdf
Version: 2018
2.6 MB
2 Downloads
Details...

 

 

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