Tuesday, May 27, 2008
218

Hibernal emergence of chironomidae in relation to stream size in kansas

Alyssa M. Anderson, R. W. Bouchard Jr., and L. C. Ferrington Jr. Department of Entomology, University of Minnesota, 219 Hodson Hall, 1980 Folwell Ave., Saint Paul, MN 55108

Historical data derived from 91 samples at 58 sample sites located on 52 springs, streams or rivers in Kansas were analyzed to determine patterns of winter-emergence of Chironomidae in relation to stream size. Fifty-three species emerged across all stream sizes during the months of December-February. Highest species richness (31) and greatest taxonomic diversity (five subfamilies: Diamesinae, Prodiamesinae, Tanypodinae, Orthocladiinae and Chironominae) emerged from springs, spring runs, and groundwater dominated small streams with maximum average widths up to two meters. Intermediate-size streams with average widths from >2 meters but <6 meters had intermediate richness (26) and were dominated by Orthocladiinae and Diamesinae. Larger rivers had substantially lower numbers of species emerging (8), and were usually dominated by species of a single genus of Orthocladiinae. Substantial groundwater inputs at springs, and into spring runs and smaller streams significantly moderates winter water temperature of these habitats, producing reaches that are locally warm and rarely freeze. We conclude that the moderating influence of groundwater strongly governs taxonomic composition and richness of Chironomidae species emerging during winter at small spatial scales and imparts the greatest impact on species composition of springs and small streams.


Web Page: Chironomidae, groundwater, winter

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