Managing Nutrient Loads to Large Waterbodies: Integrating Watershed and Coastal Perspectives

Wednesday, December 9, 2020 - 12:00pm
Peter McIntyre and Robert Mooney
Cornell University and University of Wisconsin-Madison

Excessive nitrogen (N) and phosphorus (P) loading is one of the greatest threats to aquatic ecosystems in the Anthropocene, causing eutrophication of rivers, lakes, and marine coastlines worldwide. For large lakes and marine coastlines, eutrophication is driven largely by non-point nutrient sources transported by tributaries, and management efforts tend to focus on the largest watersheds. However, the contributions of smaller watersheds, and the role of the independent dynamics of the receiving waterbody in mediating ecological consequences, are poorly understood. This webinar will use Lake Michigan as a case study for integrating extensive analyses of spatial and temporal variation in nutrient loads across watersheds with modeling of in-lake processing of these inputs. We will demonstrate the importance of land cover and dams as regulators of inputs from watersheds, including seasonal variation in their influence. Lake mixing patterns are equally dynamic across seasons and years, and we will highlight their role in mediating impacts on coastal ecosystem services. Our analyses suggest that managing nutrient loads to large waterbodies requires accounting for the heterogeneity of both watershed and coastal processes, both of which are changing with climate.