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Macroinvertebrates Testing

November 3, 2021

The Water Quality Committee and volunteers finished their planned 2021 water sampling with an assessment of the “bugs” living in the Clear Lake Watershed ditches and, for the first time, in Settlers Wetland. The “bugs” in the water are actually benthic macroinvertebrates (macros). Macros are animals that are large enough (macro) to be seen with the naked eye, lack backbones (invertebrate) and live at least part of their lives in or on the bottom (benthos) of a body of water. Examples of macros expected in our ditches include dragonfly nymphs, stonefly nymphs, dobsonfly larvae, midge larvae, beetles, snails, worms, freshwater clams, mussels, and crayfish.

Child observing the samples

Macros play an important role in the food web feeding many birds, fish and reptiles. Macros are also indicators of water quality as they react to pollution in different ways. Pollution- sensitive macros such as mayflies, stoneflies, and caddisflies are more susceptible to the effects of physical or chemical changes. Their presence indicates the absence of pollution. Pollution-tolerant macros such as midges and worms are less susceptible to physical and chemical changes in a stream indicating higher levels of pollution. When a stream becomes polluted, pollution-sensitive macros decrease in number or disappear and pollution-tolerant macros increase in variety and number.

Woman viewing macro samples

Results from this year’s sampling produced ratings of ‘Excellent’ in the Cyrus Brouse ditch and ‘Good’, ‘Fair’ or ‘Poor’ in the remaining ditches. The last few years of sampling have reflected fewer bugs. We are investigating the possible reasons.

Woman viewing macro samples
This sampling day takes place each year in September. Hands-on citizen science allows us to collect data to understand our local water quality. Pictured are members of the Water Quality Committee and volunteers sorting macroinvertebrates.

Join us next year for our annual bug sorting day. We celebrate the end of our sampling season with a bug-free lunch provided this year by Sonya Cramer and her family. Thank you to the Cramers for assisting in macroinvertebrates sampling and for providing such a delicious lunch!

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