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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #415058
Research Project: Enhancing Long-Term Agroecosystem Sustainability of Water and Soil Resources Through Science and Technology

Location: Water Quality and Ecology Research

Title: Cyanobacteria Nutrient Stressor-Response Relationships in Agricultural Watersheds of the U.S.

Author
item Lizotte Jr, Richard
item Baffaut, Claire
item JOHNSON, LAURA - Heidelberg University
item Malone, Robert
item Pisani, Oliva
item Smiley, Peter
item Williams, Mark
item Hapeman, Cathleen
item McCarty, Gregory
item Buda, Anthony

Submitted to: National Symposium on Harmful Marine Algae in the U.S.
Publication Type: Abstract Only
Publication Acceptance Date: 6/28/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: n/a

Technical Abstract: Agriculture has increased eutrophication and the potential for cyanobacteria harmful algal blooms (cyanoHABs) in freshwater systems across the United States. To help address this, USDA initiated the Conservation Effects Assessment Project and the Long-term Agroecosystem Research Network to provide information on conservation practices that will enhance agricultural sustainability and environmental integrity. From June to October 2023, 11 freshwater agricultural sub-watersheds within the Mississippi River, Ohio River, Suwannee River, Lake Erie, and Chesapeake Bay drainage basins were sampled for surface water-column cyanoHABs (monitored as phycocyanin). Laboratory bioassay (72 h) nutrient stressor-response relationships were measured to determine nitrogen and phosphorus targets for controlling cyanoHABs. CyanoHABs half-maximum effects concentrations (EC50 values) were determined from nutrient stressor-response relationships for sub-watersheds, when statistically significant (p < 0.05). Calculated EC50s are suggested as preliminary nutrient targets for assessing conservation practice effectiveness in watershed nutrient reductions. Nutrient stressor-response relationships were significant in 80-90% of bioassays in the Mississippi River Basin sub-watersheds, Suwannee River Basin, and Lake Erie. Only 35-50% of bioassays showed significant stressor response relationships in Chesapeake Bay and the Ohio River Basin sub-basin watersheds. CyanoHABs EC50 values indicated wide ranges in intra- and inter-basin nutrient targets. Nitrate EC50 values ranged from 0.022-0.695 mg/L above ambient concentrations and most (70%) were <0.200 mg/L. Phosphate EC50 values ranged from 0.004-0.159 mg/L and a majority (65%) were <0.050 mg/L above ambient concentrations. Understanding cyanoHABs nutrient stressor-response relationships can help provide clearer targets for agricultural watershed conservation strategies as tools to better manage non-point source nutrients in agricultural sub-watersheds.