Assessing Nutrient Management Strategies to Control Harmful Algal Blooms in Lake Erie

Harmful algal blooms (HAB) have impaired Lake Erie’s western basin water quality since the 1960s. Drivers of HABs are still the subject of debate and are likely the result of interactions among several biotic and abiotic factors. The problem is twofold: (1) uncertainty in the specific causes of HABs leads to inapt management solutions; and (2) managing a cross-boundary watershed requires collaboration and agreement on apt solutions from multiple stakeholders as well as many U.S. states and Canadian provinces. In this study, we use Bayesian hierarchical modeling (BHM) to investigate the relationships between nitrogen (N) and phosphorus (P) and phytoplankton biomass, cyanobacterial biomass, and microcystin concentration. We used both a within-lake and an across-lake approach and examined whether the inferences from western Lake Erie differ from the ones using multiple lakes across the country. We found that while P is still the primary driver of HABs in Western Lake Erie (WLE), the great variability between stations and months suggests that even within-lake, there may not be a single relationship characterizing phosphorus effects on HABs. We also interviewed 29 stakeholders actively involved in western Lake Erie’s watershed. We analyzed the stakeholders’ values, attitudes, and policy preferences to understand their differences or similarities and their effects on management decisions. We found that although stakeholders agree on the urgency of the problem, the different opinions and preferences of each interviewee may complicate the decision-making process in a highly collaborative watershed.Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/167292/1/2020 CIGLR Master's Project Final Report.pd