How the Distribution of Anthropogenic Nitrogen Has Changed in Narragansett Bay (RI, USA) Following Major Reductions in Nutrient Loads

摘要: Over the past decade, nitrogen (N) loads to Narragansett Bay have decreased by more than 50%. These reductions were, in large part, direct result of multiple wastewater treatment facility upgrades tertiary treatment, a process which employs N removal. Here, we document ecosystem response and assess how distribution sewage has changed from before, during, shortly after upgrades. While others observed clear responses when data were considered annually, our seasonal regional comparisons pre- post-tertiary dissolved inorganic (DIN) concentrations Secchi depth data, bay-wide surveys conducted periodically early 1970s through 2016, resulted only few subtle differences. Thus, sought use stable isotope is incorporated into ecology its may The (δ15N) carbon (δ13C) measurements particulate matter served as proxy for phytoplankton, while macroalgae short-term integrators water column bio-available N, hard clams (Mercenaria mercenaria) production. In contrast other estuarine studies that an increased influence isotopically lower marine reduced, opposite occurred Bay. effluent δ15N values at least 2‰. plants animals throughout similarly 1–2‰, on average. contrast, δ13C measured declined about same amount. results indicated that, even reductions, still plays important role supporting primary secondary production bay. However, suggests overall net decreased. 5 years major facilities came on-line nutrient removal, oligotrophication begun but remains dominant source