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Picture of a stonefly nymphStream bugs are also called "benthic macroinvertebrates." Macroinvertebrates are animals that you can see with the naked eye that don't have backbones. Some examples include insects, crustaceans, worms, snails, and clams. The term "benthic" refers to bottom dwelling animals. So benthic macroinvertebrates live in and on the bottom of the streambed and other substrates such as logs and plants in the stream channel.

King County monitors stream health by collecting samples of benthic macroinvertebrates from selected streams. Scientists use a score-card system to rank the health of the streams. The scores are based on what type of bugs are living in the stream and the number of different kinds of stream bugs present. By using this scoring system, we can compare very different streams to each other and rank their ecological health.

This site provides biological information about benthic macroinvertebrates, describes why they are important in streams, how King County uses them as stream health indicators, and information on county streams that we monitor. Next time you are walking near your neighborhood stream (after reading Your guide to visiting watersheds), carefully pick up a rock. You might be surprised at what you find!

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The Puget Sound stream benthos website is also available, developed by a group of agencies interested in monitoring the health of Pacific Northwest streams. The City of Seattle, King County, Pierce County, and Snohomish County developed the site together to share of benthic macroinvertebrate data and provides tools for calculating metrics and indices. The site is used to store and analyze data from ongoing macroinvertebrate sampling programs.

For questions about information on this page, please contact Deborah Lester, Lead, Toxicology and Contaminant Assessment Group or Kate Macneale, Environmental Scientist.