Impacts of flue gas desulfurization (FGD) gypsum on water quality and the algal community in catfish aquaculture ponds

Authors: ZINNERT, A - Auburn University; GLADFELTER, M - Auburn University; POE, H - Auburn University; TENISON, S - Auburn University; MERRILL, K - Auburn University; HENNESSEY, A - Auburn University; MCDONALD, M - Auburn University; WANG, D - Auburn University; Torbert, Henry - Allen; WILSON, A - Auburn University

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2023
Publication Date: 12/6/2023
Citation: Zinnert, A., Gladfelter, M.F., Poe, H.P., Tenison, S.E., Merrill, K.L., Hennessey, A.V., Mcdonald, M.B., Wang, D., Torbert III, H.A., Wilson, A.E. 2023. Impacts of flue gas desulfurization (FGD) gypsum on water quality and the algal community in catfish aquaculture ponds. Aquaculture. 581:740406. https://doi.org/10.1016/j.aquaculture.2023.740406.
DOI: https://doi.org/10.1016/j.aquaculture.2023.740406

Interpretive Summary: Catfish aquaculture ponds are at high risk of experiencing excessive algal growth. Conventional algaecides used in aquaculture may be effective in the short-term but can potentially lead to developed resistance in phytoplankton over time or harmful effects on non-target species. An alternative nutrient management tool, is flue gas desulfurization (FGD) gypsum, a by-product of carbon-based energy production. A six-month field experiment was conducted on active catfish aquaculture ponds to test the ability of FGD gypsum to manage excessive algal blooms throughout the growing season. In stark contrast to previous results from FGD gypsum application in eutrophic waters, this study discovered that FGD gypsum-treated ponds experienced a large increase in soluble reactive phosphorus (SRP) that led to a spike in phytoplankton abundance, specifically cyanobacteria. Overall, this experiment discovered new results that FGD gypsum can produce when used in hypereutrophic waters with nutrient-rich sediments and provides the foundation for future research directions to determine the specific mechanisms behind the interaction of FGD gypsum with the sediment.

Technical Abstract: Catfish aquaculture ponds are at high risk of experiencing excessive algal growth, especially cyanobacteria, that can lead to negative water quality issues due to their consistent input through regular feedings and internal cycling of nutrients. Conventional algaecides used in aquaculture may be effective in the short-term but can potentially lead to developed resistance in phytoplankton over time or harmful effects on non-target species. An alternative nutrient management tool, which has traditionally been used in land-based agriculture, is flue gas desulfurization (FGD) gypsum, a form of calcium sulfate that is created as a by-product of carbon-based energy sources. A six-month field experiment was conducted on active catfish aquaculture ponds at a farm in west Alabama to test the ability of FGD gypsum to manage excessive algal blooms throughout the growing season while also investigating its impacts on other water quality parameters. In stark contrast to previous results from FGD gypsum application in eutrophic waters, this study discovered that FGD gypsum-treated ponds experienced a large increase in soluble reactive phosphorus (SRP) that led to a spike in phytoplankton abundance, specifically cyanobacteria. Supplementary microcosm experiments aided in determining that FGD gypsum can pull legacy phosphorus out of the nutrient-rich, flocculant sediment found in aquaculture ponds. While these results were unexpected and ultimately undesired, we did discover that the use of FGD gypsum at the 500 mg/L concentration does not produce any trace metal contamination in the water column or in the fish tissue. Overall, this experiment discovered new results that FGD gypsum can produce when used in hypereutrophic waters with nutrient-rich sediments and provides the foundation for future research directions to determine the specific mechanisms behind the interaction of FGD gypsum with the sediment.