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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #415853
Research Project: Sustaining Productivity and Ecosystem Services of Agricultural and Horticultural Systems in the Southeastern United States

Location: Soil Dynamics Research

Title: Evaluating the tolerance of harmful algal blooms to copper sulfate pentahydrate

Author
item HENNESSEY, A - Auburn University
item MCDONALD, M - Auburn University
item JOHNSON, P - Auburn University
item GLADFELTER, M - Auburn University
item MERRILL, K - Auburn University
item TENISON, S - Auburn University
item GANEGODA, J - Auburn University
item HOANG, T - Auburn University
item Torbert, Henry - Allen
item Beck, Benjamin
item WILSON, A - Auburn University

Submitted to: Alabama Water Resources Conference
Publication Type: Abstract Only
Publication Acceptance Date: 9/4/2024
Publication Date: 9/4/2024
Citation: Hennessey, A.V., Mcdonald, M.B., Johnson, P.P., Gladfelter, M.F., Merrill, K.L., Tenison, S.E., Ganegoda, J.S., Hoang, T.C., Torbert III, H.A., Beck, B.H., Wilson, A.E. 2024. Evaluating the tolerance of harmful algal blooms to copper sulfate pentahydrate [abstract]. Alabama Water Resources Conference, Sept. 4-6, Orange Beach, AL.

Interpretive Summary:

Technical Abstract: Harmful algal blooms can cause severe economic and ecological problems, including fish mortality and the production of toxins and off-flavor compounds. These blooms often require chemical treatments, such as copper sulfate pentahydrate (CuSO4·5H2O), to mitigate damaging effects. Given that waterbodies require repeated CuSO4·5H2O treatments to control blooms, we hypothesized that phytoplankton communities treated with CuSO4·5H2O develop tolerance to treatment, which could make blooms difficult to manage over time. To test this hypothesis, the toxic effects of CuSO4·5H2O were evaluated at a standard dose (1.37 mg/L CuSO4·5H2O; 0.348 mg/L Cu) and a low dose (0.69 mg/L CuSO4·5H2O; 0.174 mg/L Cu) relative to untreated control. Treatments were applied once to 1,000 L mesocosm enclosures installed in a productive aquaculture pond at the start of the experiment and monitored for 28 days using the lab-based pollution-induced community tolerance (PICT) methodology. This method measures photosynthetic efficiency across a broad range of 0.05 to 300 mg/L Cu concentrations in acute short-term bioassays. The results of the bioassay were applied to create half-maximal effective concentration (EC50) dose-response curves that can be utilized to determine tolerance to copper. Results from this experiment indicated that both doses of CuSO4·5H2O resulted in >99% removal of cyanobacteria in the first 7 days and reduced cyanobacteria by at least 70% throughout the experiment. In the first 3 days, communities in the standard dose and low dose treatments were 20x and 10x more tolerant, respectively. Tolerance peaked at 14 days after the treatments were applied and remained higher than the control throughout the experiment. These data suggest that a lower dose of copper sulfate is equally effective at treating harmful algal blooms dominated by cyanobacteria and that higher doses can lead to higher tolerance in the system, making blooms more difficult to treat in the future.