PALEOECOLOGY SUPPORTS THE MANAGEMENT OF ANTHROPOGENIC NUTRIENTS IN THE LAURENTIAN GREAT LAKES

Recent monitoring data have revealed significant changes in whole-lake conditions in the Laurentian Great Lakes, particularly within the last decade. In most cases trends indicate a drop in algal abundance resulting from the effects of reduced nutrients, both through reduction in watershed flux and recent spread of invasive species. Not surprisingly, those responsible for tracking and maintaining ecosystem services on the Great Lakes are concerned about the ecological trajectories of the lakes.

Contemporary monitoring alone is not always sufficient to answer important management questions, so we are employing paleolimnology to put modern conditions in a long-term context. Paleolimnology uses lake sediment components to infer past conditions and uncover trends in environmental quality. These retrospective data are needed to distinguish natural from human trends, and to reveal the causes and magnitudes of environmental insults that inform management matters regarding climate change, pollution and invasive species. The cornerstone of many previous paleolimnological investigations has been the use of diatoms, known powerful indicators of environmental change. The diatom algae from the Great Lakes have been calibrated to nutrients, and a diatom-based phosphorus model is being used in a paleolimnological investigation the trophic histories of the lakes and how they relate to human activities in their watersheds. This is complicated by the fact that multiple stressors are acting on the lakes. Changes in climate are also affecting their physical properties, which is in turn causing a shift in species composition. Investigations are continuing to describe the anthropogenic history of degradation and remediation in all of the lakes. It is anticipated that algal indicators and paleoecological applications will serve to address the many environmental issues that require long-term data in order to make remedial decisions.