265 



incursions into low salinity marshes and mangrove swamps and 

 large salinity fluctuations in freshwater outlets to the ocean, 

 leading to massive shifts in species composition in these areas. 



A natural tendency exists for portions of the New York Bight to 

 become anoxic under certain conditions. However, records 

 indicate anoxic events probably occurred in this region prior to 

 the effects of urbanization. Oxygen depletion is a natural 

 feature of ocean areas where there is a high productivity and 

 restricted vertical mixing and flushing of bottom water, such as 

 observed in the Cariaco Trench and Black Sea (Richards 1965), 

 the Baltic Sea (Kaleis 1976), and off the west coast of Africa 

 (Harvey 1963). The organic and nutrient inputs of man to the 

 New York Bight, which are predominantly- §tom the Hudson-Rariben 

 estuary, may have increased the chance that such anoxic events 

 ■_will reoccur in the New York Bight under certain unusual 

 hydrographic conditions. However, it has been shown 

 unequivocally that the disposal of sewage sludge at the 12-Mile 

 Site is not a significant factor affecting the likelihood of 

 anoxia in the New York Bight. Severe anoxic events and low 

 oxygen levels are occurring with increasing frequency in other 

 coastal regions of the U.S. and the world where large human 

 populations impinge on a coastal region. For example, the 

 Chesapeake Bay is experiencing annual severe oxygen depletion in 

 its upper reaches which has led to the loss of large populations 

 of commercial shellfish (Heinle et al . 1980). 



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