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TRENDS IN INDICATORS OF EUTROPHICATION IN WESTERN LONG ISLAND SOUND AND THE HUDSON-RARITAN ESTUARY
Citation:
O'Shea*, M L. AND T. M. Brosnan. TRENDS IN INDICATORS OF EUTROPHICATION IN WESTERN LONG ISLAND SOUND AND THE HUDSON-RARITAN ESTUARY. To be submitted to the 15th Annual Internation Estuarine Research Federation Conference, New Orleans, LA, 9/25-30/99.
Description:
Significant improvements in water quality have been observed for several decades throughout much of the Hudson-Raritan Estuary, largely as a result of regional abatement of municipal and industrial discharges. these improvements include area-wide, order-of-magnatude reductions in ambient coliform concentrations, and significant increases in dissolved oxygen (DO) concentrations. However, in contrast to these improvements, dissolved oxygen in bottom waters of the western Long Island Sound (WLIS) appears to have decreased in the last two decades. although there is no consensus as to why hypoxia in WLIS may have recently become more severe, several related hypotheses have been suggested, including an increase in eutrophication, increased density stratification, or changes in wastewater loads. To determine if eutrophication has increased in WLIS, trends in several indicators of eutrophication were examined from a long term water quality dataset. since the mid-1980s surface DO supersaturation has increased, bottom minimum DO has decreased, and vertical DO stratification has increased in WLIS. The data also suggests an increase inchllorophyll a concentrations, and decrease in Secchi transparency in recent years, but no trend in dissolved inorganic nitrogen or phosphorus. Some of these trends are also apparent in other eutrophic areas of the Hudson-Raritan Estuary. Temporal changes in vertical density stratification, wastewater loads, and changes to upstream and nonpoint source loads are each examined for their potential role in these water quality trends.