Date of this Version
McCright, C., McCoy, J., Robbins, N., Comfort, S. (2022). Use of Lanthanum in Slow-Release Composite to Treat Eutrophic Ponds does not Accumulate in Fish Tissue.
Nutrient runoff is a major water quality issue affecting residential and recreational water resources. Excess nutrients like nitrate and phosphate entering the water column promote eutrophication. We previously showed that floating treatment wetlands combined with slow-release lanthanum composites inserted in airlift pumps can reduce N and P concentrations, minimize algae and weed growth and increase dissolved oxygen concentrations. While water quality improves following this biological and chemical approach, questions remained about the toxicity and potential accumulation of lanthanum in lentic organisms. Therefore, our objective was to analyze fish samples to determine the presence, concentration, and location of lanthanum accumulation. We analyzed the tissue and liver samples of fish exposed to the field treatment for two years versus a control field pond. We also conducted a controlled tank study that used higher lanthanum concentrations than those observed in the field. The field study confirmed that under the concentrations of lanthanum released to treat eutrophic ponds, no adverse effects were observed in harvested fish. We observed increased mortality and higher trends toward significance in the fish exposed to lanthanum in the tank study. However, no significant differences were found between lanthanum exposed and unexposed fish (α=0.05). Given the laboratory tank lanthanum concentrations were nine times higher (916 µg/L) than the observed field concentrations (104 µg/L), we conclude the slow-release lanthanum composite used to treat eutrophic ponds exhibits no significant accumulation in fish tissue, minimizing any risk to the fishing public. These data support the slow-release lanthanum composites as an effective strategy for treating eutrophic ponds.