Lake Erie Research: Recent Results, Remaining Gaps

Abstract

Evidence that oxygen depletion rates in the central basin hypolimnion were increasing and would lead to increasingly severe late summer anoxia resulted in a large public investment in both the U.S. and Canada to construct sewage treatment plants in order to reduce the phosphorus load to Lake Erie. Improvements in the water quality indicators, phosphorus and chlorophyll, have been achieved in the decade since these measures went into effect. There is no clear evidence, however, for a corresponding “recovery” in hypolimnetic oxygen depletion. It is now recognized that physical processes, driven by winds and solar heating with strong interannual fluctuations, influence the timing and severity of late-summer anoxia, and make it difficult to detect long-term trends. As a result of the 1979 and 1980 intensive field experiments, many of the physical processes are better understood, better documented, and new possibilities exist for improved numerical hydrodynamical modeling. Systems modelers have exploited the voluminous Lake Erie data to generate convincing water quality models that account for the physical variability as well as simulating biochemical parameters. In some respects the modelers have pushed beyond the frontiers of established knowledge of biochemical processes and thus challenge process-oriented researchers to confirm or reject their findings. A consensus is forming among Lake Erie researchers that the key to understanding the lake's response to changing external loading lies in a detailed understanding of the sediment/water interaction. Study of sediment-water interactions calls for interdisciplinary efforts that will involve physicists, biologists, chemists, and modelers. An appendix to this paper lists specific research recommendations.