Seasonal and spatial effects of wastewater effluent on oyster growth, survival, and accumulation of pathogens in Mobile Bay, Alabama

Each year millions of gallons of wastewater (WW) are discharged into estuarine waters; understanding the impacts of sewage inputs is critical to the protection and management of these waters. I assessed the ecological and human health effects of municipal waste treatment plant (WTP) effluent on oysters in Mobile Bay, AL across multiple seasons and at varying distances from the WTP outfall. Nutrient concentrations, isotope influence from the WTP, and Sewage-associated microbes were higher at sites closer to the WTP. However, chl a concentrations and also oyster growth did not show a relationship to proximity to the WTP; chl a and oyster growth showed the greatest differences among seasons. In summer and fall, the seasons when oysters were growing but freshwater discharge to Mobile Bay was relatively low, microbial indicator species correlated with ∂ 15N values in oysters. These data will be useful to guide municipal waste management, refine boundary determinations for shellfish area closures, reduce the likelihood of harvesting contaminated shellfish, and enhance local coastal economies that depend on commercial shellfisheries.