Refining knowledge of biogeochemical cycling and ecological interactions within the Lake Erie watershed

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Harmful algal blooms (HABs) and low dissolved oxygen (DO) levels are major concerns in large waterbodies, and have been linked with high phosphorus inputs and intensified algal growth and decay. While watershed management plans have helped to reduce nutrient loads received by lakes, HAB frequency has recently increased and DO concentration targets have not consistently been met, particularly in the Laurentian Great Lakes. This failure of management strategies has been linked to increasing availability of certain fractions of phosphorus, despite declines in the total loads, and attributed to complex local interactions between land management approaches, climate change and long-term soil storage. Although there are many theories as to the nutrient sources, a solution to their availability and that of the recurring HABs has not yet been found.Recent management failures result from our incomplete knowledge of nutrient transport mechanisms, complex process interactions and associated lake biogeochemical responses. Until these knowledge gaps are filled, the potential effects of new management strategies cannot be predicted. This research program will improve our knowledge of threshold drivers of HABs and lake health through deploying mobile monitoring units around the watershed of Lake Erie, monitoring physical, chemical and biological interactions across land, river, shoreline and deep lake interfaces at hourly intervals.Models remain the best available tools to simulate efficacy of management strategies, however they are only as accurate as our process understanding. Historically observational uncertainty and a lack of biogeochemical knowledge has obstructed models from generating helpful management solutions to eutrophication issues. Using the new monitoring data a catchment-lake model will be implemented, with reduced observational uncertainty, to simulate sediment, chemical, hydrological and biological fluxes through the terrestrial, riverine and lake corridor. Land management strategies for reducing frequency of occurrence of HABs and increasing lake DO concentrations will be simulated, and their long term resilience assessed under potential future changes in climate and land-use.Improvement of our understanding of interactions between land management and aquatic ecosystems benefits policy makers, residents and users of the lake by generating new information on areas particularly vulnerable to change (hotspots), highlighting areas for management priority and generating novel, more resilient management strategies enabling a healthier lake to be sustained in the face of future change. The large database of high resolution monitoring information generated will be beneficial to a wide range of users, including government (MOECC and EC), local landowners, industry (water treatment plants), and other researchers.