Effects of Reservoir Drawdown on Riffle Macroinvertebrate Communities

In 2007 Keystone Pond, a reservoir behind the Boardman dam, Boardman River, Grand Traverse County, Michigan, USA was drawn down in preparation for dam removal. The objective of this study was to quantify the effects of drawdown on benthic macroinvertebrate riffle communities by comparing a downstream site in a newly formed channel to an upstream control. Since 2008 a total of 2338 macroinvertebrates have been sampled and identified to the lowest practical taxonomic level. Data were analyzed using Chi-Square goodness of fit tests, Simpson’s Index of diversity, and Sorensens' Quotient of Similarity. We found that macroinvertebrate communities in the new channel have recovered to a more natural condition and show increasing similarity to the upstream control site Hayes & Mahan 2