Tuesday, June 5, 2007
417

Aquatic macroinvertebrate community response to regional sediment loads in macrophyte beds of a prairie pothole lake

Kristopher G. Dozark and Nels H. Troelstrup Jr., Professor. Biology and Microbiology, South Dakota State University, 510 8th Street S #18, Brookings, SD 57006

Sediment has been shown to alter aquatic habitat, smother indigenous fauna, clog respiratory and feeding apparatus, contribute metal contamination and scour organisms within stream and lake habitats. However, the effects of changing sediment load on invertebrate biotic integrity are not well documented.  This study examined macroinvertebrate community structure responses to experimental sediment loads within a prairie lake littoral.  Five treatment plots (1m x 4m) were constructed within 10 emergent macrophyte stands of Oak Lake, South Dakota at pulsed loading rates equal to annual regional ranges (0, 250, 2500, 25000, and 250000 Kg/Ha/Yr). Invertebrates were collected 1 week prior and 1 and 2 weeks following treatment using a petite dip net (500 um).  Percent abundance of collector-gatherers was reduced (7.7%) in high treatment plots (ANOVA p < 0.01). However, Diptera richness, Ephemeroptera richness, Hilsenhoff’s Biotic Index, percent Chironomidae, percent dominant taxon, percent gliders, percent Insecta, percent predators, and percent swimmers were not significantly different from control plots.  Thus, sediment loads within the regional range had little effect on depositional shoreline communities.  Additional treatments to rocky shorelines would allow comparison of loading effects between depositional and erosional habitats comprising 70% of shoreline perimeter.   

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