At the end of each summer, staff from the Public Works Department put on their rubber boots and head out to local creeks to collect samples of stream bugs. The scientific term for these creatures is “benthic macroinvertebrates” (benthic = bottom dwelling, macroinvertebrates = large animals without backbones), but that doesn’t exactly roll off the tongue, so we usually just call them “stream bugs.”

These bugs that live on the bottom of streambeds – mayflies, stoneflies, snails and many other invertebrates – are great indicators of a watershed’s health, so we collect bugs annually to see how Kirkland’s watersheds are doing. The bugs are one of the “vital signs” of a healthy ecosystem, as they play a crucial role in the stream nutrient cycle; the absence of certain species in a stream can signal a problem; and bug population fluctuations can indicate a change (good or bad) in a stream.

Once we finish collecting in each stream, the bug samples are shipped off to a lab where they are sorted, analyzed and used to calculate the benthic index of biotic integrity (B-IBI), also called “the bug index.” This index is a synthesis of a lot of information to assess the biological condition, or health, of streams. The bug index is composed of ten “metrics.” The metrics measure different aspects of stream biology, including the diversity of bug species, number of bugs, and population structure.

The presence or absence of certain bugs can also tell a bigger story about pollution. Some stream bugs like stoneflies and mayflies, aren’t very tolerant of pollution, so finding a lot of these bugs tells us we have clean creeks. On the other hand, bugs like aquatic worms and snails are very tolerant of pollution. If we find a lot of these bugs and we don’t also see some of the pollution intolerant bugs, this can ring alarm bells for creek health.

By annually calculating the bug index for Kirkland’s streams, we can see if streams are changing over time. When bug index values are lower than expected, we can investigate what is happening in the watershed that might be degrading stream health.

Now you can follow along each year as we collect our data! Our online interactive watershed dashboard allows you to view our annual water quality and stream bug scores for creeks across Kirkland.