¹U.S. Environmental Protection Agency, Mid-continent Ecology Division, 6201 Congdon Blvd., Duluth, MN, 55804, USA
²National Oceanic and Atmospheric Agency, Great Lakes Enviromental Reserarch Laboratory, 2205 Commonwealth Blvd., Ann Arbor, MI, 48105, USA

Summary

         Recent changes to benthic communities in the lower Laurentian Great Lakes raise concerns about the status of benthic macroinvertebrates in Lake Superior. This lakewide study was conducted to ascertain their status in nearshore waters of Lake Superior. Benthic macroinvertebrates were collected from 27 sites representing the U.S. nearshore waters (20 to 110 m) of Lake Superior in 1994, 2000, and 2003. No significant differences in total benthic macroinvertebrate abundance, or abundances of oligochaetes, clams, or chironomids were detected among years. Abundance of the amphipod Diporeia was lower in 2000 than in 1994 or 2003. The oligochaete trophic index, a measure based on tolerance of oligochaete species to organic enrichment, did not differ between years. Diporeia exhibited a bimodal depth distribution, with peaks in abundance at depths of 30 to 40 m and 60 to 70 m. Oligochaetes were most abundant at 50 to 60 m depth, clams between 30 and 70 m, and chironomids at less than 30 m. The spatial and temporal variability observed in Lake Superior’s benthic macroinvertebrate communities has implications for environmental assessment.