Agricultural conservation practices could help offset climate change impacts on cyanobacterial harmful algal blooms in Lake Erie

Authors: FRAKER, MICHAEL - University Of Michigan; ALOYSIUS, NOEL - University Of Missouri; MARTIN, JAY - The Ohio State University; KEITZER, S - Tusculum University; DIPPOLD, DAVID - The Ohio State University; YEN, HAW - Blackland Research And Extension Center; Arnold, Jeffrey; DAGGUPATI, PRASAD - University Of Guelph; JOHNSON, MARI-VAUGHN - Us Geological Survey (USGS); ROBERTSON, DALE - Us Geological Survey (USGS); SOWA, SCOTT - The Nature Conservancy; White, Michael; LUDSIN, STUART - The Ohio State University

Submitted to: Journal of Great Lakes Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2022
Publication Date: 2/1/2023
Citation: Fraker, M.E., Aloysius, N.R., Martin, J.F., Keitzer, S.C., Dippold, D.A., Yen, H., Arnold, J.G., Daggupati, P., Johnson, M.V., Robertson, D.M., Sowa, S.P., White, M.J., Ludsin, S.A. 2023. Agricultural conservation practices could help offset climate change impacts on cyanobacterial harmful algal blooms in Lake Erie. Journal of Great Lakes Research. 49:209-219. https://doi.org/10.1016/j.jglr.2022/11.009.
DOI: https://doi.org/10.1016/j.jglr.2022/11.009

Interpretive Summary: Harmful algal blooms (HABs) have become a recurring problem in temperate freshwater lakes and coastal marine ecosystems, primarily due to excess nutrients entering the water bodies. Implementation of agricultural conservation practices (ACPs) offers a means to reduce agricultural nutrient runoff and mitigate HABs. However, the effectiveness of ACPs in a changing climate remains uncertain, given that increased temperature and precipitation could potentially increase the frequency and magnitude of HABs. In this study, an integrated biophysical modeling approach was used to project how Lake Erie HAB severity might change under several climate and ACP implementation scenarios, using western Lake Erie and its largely agricultural watershed as our study system. Climate scenarios (future precipitation and temperature) were derived using climate model output for both a moderate mitigation scenario and a business-as-usual scenario. Climate from these scenarios were input to the USDA Conservation Effects Assessment Project (CEAP) model to determine the impacts of ACPs on nutrient concentrations entering Lake Erie. Model results showed that without changes in ACPs, HAB severity will increase in coming decades. Results also show that widespread implementation of ACPs appear capable of counteracting the increase in HABs. This study provides a biophysical modeling approach to help identify strategies and develop policy to mitigate HABs under changing climate conditions.

Technical Abstract: Harmful algal blooms (HABs) have become a recurring problem in temperate freshwater and coastal marine ecosystems, owing to human-driven nutrient pollution. Implementation of agricultural conservation practices (ACPs) offers a means to reduce non-point source nutrient runoff and mitigate HABs. However, the effectiveness of ACPs in a changing climate remains uncertain, given that increased temperature and precipitation have been hypothesized to increase the frequency and magnitude of HABs. Herein, an integrated biophysical modeling approach was used to project how Lake Erie HAB severity (estimated bloom biomass) might change under several climate and ACP implementation scenarios, using western Lake Erie and its largely agricultural watershed as our study system. An ensemble of general circulation model projections was used to drive spatially-explicit land use and hydrology models of the Maumee River watershed, the output of which informed a predictive model of Lake Erie HAB severity. Results show that, in the absence of changes in ACPs, the frequency of severe HABs are projected to increase during coming decades, owing primarily to increased inputs of nutrients from the watershed. These anticipated increases are due both to increased total precipitation and more frequent, higher-magnitude rainfall events. While implementation of ACPs appear capable of counteracting the increase in HABs, widespread implementation would be necessary to reduce HAB severity below current management targets. This study highlights how continued climate change will only exacerbate the need for land management practices that can reduce nutrient runoff in agriculturally dominated temperate ecosystems, such as Lake Erie, and shows how interdisciplinary, biophysical modeling approaches can help identify strategies to mitigate HABs in the face of other anthropogenic stressors.