Oxygen depletion in Long Island Sound : a historical perspective

摘要: A retrospective analysis of available data was conducted to characterize the spatial distribution and temporal trends in dissolved oxygen (DO) concentrations Long Island Sound (LIS) over past four decades. general east-to-west gradient decreasing bottom DO evident all historical examined. In our review from 1950s, collected by Gordon Riley colleagues, contemporary surveys, we found no evidence hypoxia (DO≤0.3, mg 1−1) Eastern Basin; however, deeper waters Central Basin, there is some for a recent (1986) emergence moderate hypoxia. The Western Basin experienced episodes during 1970s which became more recurrent possibly severe late 1980s. most severe, persistent chronically occurred throughout water column East River Narrows. An unprecedented episode anoxia observed both Narrows regions LIS 1987. Previously, rarely, short-lived, confined River. Statistical trend analyses revealed significant increase summer minimum lower middle reaches 20 years. Beginning 1981, declined markedly adjacent bordering Nassau County nearshore. improvements quality previous 15–20 years appear have been gained at the, expense poorer western sound. Mechanisms potentially responsible decline are suggested.