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CHIRONOMID EMERGENCE AS AN INDICATION OF TROPHIC STATE IN MINNESOTA SENTINEL LAKES

We assessed emergence of Chironomidae in a subset of Sentinel lakes with differing trophic states (e.g., total phosphorus = 5.6-132 micro g/l) in Minnesota. Emergence composition at genus level was determined in 2014 using two or more collections of Chironomidae surface-floating pupal exuviae per lake. In total, we documented 59 genera. Genus composition by lake varied from 16 to 35, but did not strongly coincide with lake trophic state, except for slight decreases in eutrophic-to-hypereutrophic lakes. Jaccard’s Similarity Coefficient, which quantifies community associations, ranged from 28.1% to 66.7% (Avg= 45.8%; sd = +/- 8.7%) between lakes, and average similarities declined with increasing differences in trophic state. Orthocladiinae and Tanytarsini were proportionally more abundant in lower nutrient lakes and Chironomini proportionally more abundant in eutrophic and hypereutrophic lakes, a pattern that has been observed in lakes based on dredge samples for larvae or emergence samples for adults. Our results demonstrate that collections of Chironomidae surface-floating pupal exuviae can be used to monitor community patterns across a wide range of lakes with differing trophic states.

Corrie Nyquist (Primary Presenter/Author), University of Minnesota, nyqui095@umn.edu;


Leonard Ferrington, Jr. ( Co-Presenter/Co-Author), University of Minnesota, ferri016@umn.edu;


Alexander Egan ( Co-Presenter/Co-Author), University of Minnesota, egan0059@umn.edu;


Petra Kranzfelder ( Co-Presenter/Co-Author), University of Minnesota, kranz081@umn.edu;