Examining effects of sedimentation on aquatic invertebrate communities of Oak Lake

Dozark, K.G. and N.H. Troelstrup, Jr.

Sediment has been shown to alter aquatic habitat, smother indigenous fauna, clog respiratory and feeding apparatus, and contribute metal contamination. This study examined macroinvertebrate community structure responses to regional sediment loads in a field experiment. Five treatment plots (1m x 4m) were constructed within 10 macrophyte beds (2006) and 10 rocky shore habitats (2007) of Oak Lake. The treatment levels (0.0 Kg, 0.1 Kg, 1.0 Kg, 10 Kg, and 100 Kg) were based on regional sediment loads. Invertebrates were collected once prior and twice following treatment with a 500 mm petite net. A total of 300 organisms were subsampled from each sample and identified to the lowest practical taxonomic level. Substrate particle size, stem density, turbidity, water temperature, conductivity, pH, and dissolved oxygen were sampled. No community associations with sediment have been found in the macrophyte bed plots. The rocky shore plots are in the preliminary stages of being sorted and identified. The substrate particle size does show a treatment effect in both habitats. Ninety-eight taxa have been identified in the samples, with four genera added to the Oak Lake taxa list. Three are from macrophyte beds and one from rocky shore habitat. They consist of three insects and one crustacean. Together, rocky shoreline and emergent beds contribute over 90% of shoreline littoral habitat. Load-response relationships established from this study will facilitate TMDL development to support biological use criteria in prairie pothole basins. (Presentation pdf)