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SFS Annual Meeting

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Chironomids display thermal partitioning on an annual basis with different taxa emerging under specific temperature regimes in streams. Research on chironomid emergence indicates that similarities in emerging taxa decrease over time as the amount of time between emergences increases. In Southeastern Minnesota, cold-adapted taxa predominantly emerge during the winter, and warm-adapted taxa typically emerge during spring and summer. Thus, the composition of emerging taxa changes over the course of a year. This study assesses the similarities and rate of change in emerging chironomid taxa across study months in an urban trout stream. The trout stream, located in South Central Minnesota, was assessed from July 2006 to June 2007. Similarities and rates of change in emerging chironomid taxa were quantified using Jaccard’s Similarity Index. On average, 48.1% of emerging taxa were shared between adjacent months. In contrast, an average of 23.1% of taxa were shared between months that were half a year apart. Months with the most contrasting air temperatures (e.g. July and January) had the largest rate of change between comparisons (100% different). Our results indicate that the taxonomic composition of emerging chironomids differs more as time between emergences increases.

Corrie Nyquist (Primary Presenter/Author), University of Minnesota,;

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