Sediment effects on aquatic macroinvertebrates in a prairie pothole, Oak Lake, in eastern South Dakota

The Clean Water Act aims to maintain the physical, chemical, and biological integrity of the nation's waters. Sedimentation is a major pollutant to world, national, and state waterbodies. The developments of Total Maximum Daily Loads (TMDLs) are required to improve water quality problems through the use of Best Management Practices (BMPs). Sedimentation can be detrimental to aquatic ecosystems by reducing feeding ability, smothering habitat, clogging respiratory apparatuses, and increasing scouring and abrasion to exoskeletons of aquatic organisms. This study examined the influence of regional sediment loads on aquatic macroinvertebrate communities in the littoral zone of a prairie pothole lake, Oak Lake. Ten emergent macrophyte bed and ten rocky shoreline locations were treated with varying levels of soil to simulate regional sediment loads of 25 tons/km2, 250 tons/km 2, 2,500 tons/km2 and 25,000 tons/km2. Five plots were treated and sampled at each of ten locations during the summers of 2005 and 2006. Invertebrates were subsampled, identified to the lowest practical taxonomic level, and classified into habitat and feeding guilds. A total of 129 invertebrate taxa were identified throughout the experiment. Macrophyte beds contained an average of 23 genera and rocky shores contained an average of 18 genera. Sedimentation significantly decreased the percentages of collector-gatherers and sprawlers in both habitats. Percentages of gliders, swimmers, and scrapers increased with the addition of sediment in both habitats. Macrophyte beds exhibited an increase in Ephemeroptera, Trichoptera, and Odonata richness following sedimentation. The percentage of sprawlers in rocky shorelines was significantly decreased due to sedimentation. These relationships were log linear. Oligochaeta, Caenis latipennis, Endochironomus and Coenagrionidae abundances were reduced following treatment in macrophyte beds. In rocky habitats abundances of Oligochaeta, water mites, and Hyalella azteca increased following treatment. However, Caenis latipennis and Hydra abundances decreased. Overall, macroinvertebrate communities changed little following sedimentation. Other studies suggest that macroinvertebrate communities in the Prairie Pothole region are tolerant to environmental disturbances and changes. Non-anthropogenic factors, such as lake morphology, may be more influential to macroinvertebrate communities than anthropogenic factors, such as human development along lake shorelines. Future studies should examine possible macroinvertebrate threshold levels with higher sediment loads than were used in this study.