Report to the Towns of Brookhaven and Islip, N.Y. on the hydrography of Great South Bay and Moriches Bay

Abstract

During the summer of 1950, The Woods Hole Oceanographic Institution conducted a study of the waters of Great South Bay for the Town of Islip, New York, with a view to seeking the cause of the decline of the oyster industry, which has deteriorated steadily during the past twenty years. The report of these studies was submitted in January 1951. The survey revealed two conditions which in combination appeared to be unfavorable to the oyster industry. One unfavorable condition was the local change in circulation occasioned by the opening of Moriches Inlet in 1931, which had increased the salinity of Bellport Bay, creating a condition which might well be detrimental to the production of seed oysters. Aside from this, it was concluded that little change had taken place in the salinity and tidal exchange of the central and western part of the bay during the past twenty years. The second unfavorable condition was the pollution of Great South Bay by wastes from the duck farms located along the Carmans River and the tributaries of Moriches Bay. Chemical studies indicated that the bay water is unusually rich in the products of decomposing organic matter. These materials appeared to arise from the mouth of the Carmans River and the tributaries of Moriches Bay, from which they are carried westward across Great South Bay. They provide nutriment for the growth of an unusually dense population of microscopic plants. Evidence existed that oysters do not feed properly on water containing such large concentrations of plant cells, and available statistics showed a clear correlation over a period of years between the condition of bay oysters and the numbers of plant cells in the water. Finally, the decline in oyster production has been closely paralleled by the growth of the duck industry, which increased fourfold during the period. In the report on the survey of 1950, it was pointed out that a number of questions had been revealed which were not anticipated when the field work was in progress and that these questions merited additional study. One of these related to the behavior of uric acid, the peculiar form in which birds secrete nitrogenous wastes, which promised to provide unambiguous evidence on whether the duck farms are the source of pollution. Another was the more detailed study of the circulation of Moriches Bay and its connection with Great South Bay through Narrow Bay, since this appeared to be the principal avenue of the pollution of Great South Bay. Finally, more detailed information was desired concerning the actual quantities of pollutants arising from the duck farms and of the alterations of its components by biological and other action upon introduction into the bay water. Before these additional studies could be undertaken, the problem acquired a new aspect be cause of the spontaneous closure of Moriches Inlet which occurred on May 15, 1951. While this terminated any possibility of increasing knowledge of the circulation between the bays as it previously existed, it afforded an opportunity to observe the effect of the opening on the condition of the bay waters. This information was of prime importance in view of the proposal to reopen and stabilize Moriches Inlet. Field parties visited the region on three occasions during the sumer. On July 12-14, 1951, a survey was made of the entire system of bays lying between the western extremity of Great South Bay and the Shintecock Canal. Between July 27 and August 5, studies were made of the chemical conditions in Moriches Bay and its approaches, and a detailed examination was carried out on the immediate conditions associated with the duck farms along the Terrell River. On September 24-29, an attempt was made to measure the exchange of water and associated pollutants between Moriches Bay and Great South Bay, and through the Quantuck Canal. On this occasion continuous observations were made at Smith Point and Beach Lane Bridge for a period of fifty hours, including four complete tidal cycles.