Associations among Chironomidae and Sandy Substrates in Nearshore Lake Michigan

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Abstract
Chironomids and sediments were collected at 3- to 15-m depths along the shoreline of eastern Lake Michigan from 1978-1980. Chironomids were the most frequently occurring (92% of samples), most diverse (41 taxa), and the second-most numerous (1634 .cntdot. m-2) group in this depth regime. The generalized sediment type was moderately [percent weight per grain size unit] sorted, fine sand. Sediments were grouped into 3 categories roughly corresponding to coarse (< 2 .vphi.), fine (2-3 .vphi.) and very fine (.gtoreq. 3 .vphi.) sands. Nonparametric tests and a comparison of frequency distributions and densities distinguished chironomid-substrate associations. Two species were strongly associated with coarse sand, 5 spp. with coarse-fine sands and fine-very fine sands and 11 spp. with very fine sand. Observed chironomid-substrate associations probably were related in part to morphological differences among taxa. Species most strongly associated with coarse sediments were small, slender and fast-moving forms with tough outer body integuments, morphological characteristics that are necessary for survival in the ephemeral, physically controlled environment. In the more stable, predictable environment where fine and very fine sands were most evident, species exhibited a wider variety of morphological characteristics, which included soft-bodied, tubicolous forms.

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