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Some Challenges of an “Upside Down” Nitrogen Budget – Science and Management in Greenwich Bay, RI (USA)
DiMilla, P. A., S. W. Nixon, A. OCZKOWSKI, M. A. Altabet, AND R. A. MCKINNEY. Some Challenges of an “Upside Down” Nitrogen Budget – Science and Management in Greenwich Bay, RI (USA). MARINE POLLUTION BULLETIN. Elsevier Science Ltd, New York, NY, 62(4):672-680, (2011).
This work challenges the notion that the predominant sources of nitrogen to an estuary are from its watershed. This study demonstrates that the largest source of nitrogen to Greenwich Bay, Rhode Island is the adjacent Narragansett Bay and, more specifically, the Providence-Seekonk River Estuary. A fairly recent fish kill in Greenwich Bay has politicized and intensified management efforts in this system, but the focus has been almost exclusively on reducing watershed sources. Our research challenges this sole focus.
When nutrients impact estuarine water quality, scientists and managers instinctively focus on quantifying and controlling land-based sources. However, in Greenwich Bay, RI, the estuary opens onto a larger and more intensively fertilized coastal water body (Narragansett Bay). Previous inventories of nitrogen (N) inputs to Greenwich Bay found that N inputs from Narragansett Bay exceeded those from the local watershed, suggesting that recent efforts to reduce local watershed N loads may have little effect on estuarine water quality. We used stable isotopes of N to characterize watershed and Narragansett Bay N sources as well as the composition of primary producers and consumers throughout Greenwich Bay. Results were consistent with previous assessments of the importance of N inputs to Greenwich Bay from Narragansett Bay. As multiple N sources contribute to estuarine water quality, effective management requires attention to individual sources commensurate with overall magnitude, regardless of the political complications that may entail.