Wetlands provide many valuable ecosystem services, including water quality improvement to protect downstream aquatic ecosystems such as lakes, rivers, and estuaries. However, their ability to improve water quality to safe levels for direct human exposure while largely surrounded by agricultural lands and hosting large wildlife populations remains unknown. Our aim was to examine the ecosystem service capabilities of an avian-dense coastal wetland surrounded by agricultural lands along the southwestern shore of Lake Erie in Ohio by assessing the quality of water as it flows through the wetland (Ottawa National Wildlife Refuge (ONWR)) and into Lake Erie beach waters. Our study used total phosphorus and fecal indicator (Escherichia coli) concentrations as water quality metrics across the wetland and at an adjacent Lake Erie swimming beach during the 2012 summer swim season. E. coli and total P levels were consistently highest at the site, where water enters the ONWR (mean E. coli = 507 CFU/100 mL; mean total P = 535 μg/L), and steadily decreased as water flowed through the wetland and into the adjacent beach (mean E. coli = 10 CFU/100 mL; mean total P = 41 μg/L). E. coli and total P showed statistically significant (α = 0.01) correlations with phycocyanin, chlorophyll-a, turbidity, specific conductivity, dissolved oxygen, and pH; total P was also significantly correlated with total N. The results suggest that this wetland may be contributing to improving water quality, which is beneficial for human health as well as to downstream ecosystem health (e.g., limiting eutrophication promoting conditions, etc.).