A Chironomid-Based Paleolimnological Assessment of Long-Term Cumulative Effects Of Multiple Anthropogenic Stressors on Hypolimnetic Oxygen Dynamics in Lake Erie

The central basin of Lake Erie is annually subjected to hypoxia, which has implications for fish communities and nutrient recycling. As limnological monitoring data for Lake Erie does not extend beyond the 1970s, paleolimnological techniques can be used to reconstruct long-term water quality trends. Chironomidae (Diptera) remains preserved in dated sediment cores from the western, central, and eastern basins in Lake Erie were used to assess the long-term cumulative effects of multiple anthropogenic stressors on hypolimnetic dissolved oxygen. Results from analyses of subfossil chironomid remains indicated that the central basin has exhibited mesotrophic to eutrophic conditions since 1850. However, a transition in chironomid communities further towards anoxic-type taxa between 1930-1950 suggests that the severity and duration of hypolimnetic anoxia has increased in recent decades. Variance partitioning analysis (VPA) indicated that the effects of land use and climate had significant implications in driving changes in chironomid assemblages in the central basin.