60 



Table 4-1. 



Navigation Positions of Future Disposal Mounds 



Approximate Location 



Longitude, NAD 27 



Latitude, NAD 27 



South of the G mound 1 



073° 29.088' W 



40° 59.100' N 



C-E 2 



073° 28.794' W 



40° 59.280' N 



E-H 3 



073° 28.932' W 



40° 59.376' N 



West of survey area 4 



073° 29.406' W 



40° 59.274' N 



5 



073° 29.442' W 



40° 59.220' N 



6 



073° 29.406' W 



40° 59.154' N 



4.1.2 Dissolved Oxygen in Western Long Island Sound 



Since 1985, hypoxia (low dissolved oxygen conditions) and its associated 

 complications with benthic recolonization have been documented in DAMOS monitoring 

 reports of WLIS (Morris 1998, SAIC 1987). Because of these complications in the 

 summer, the monitoring survey was scheduled for late-September after the fall turnover of 

 the water column. The western half of the Sound becomes hypoxic in the late summer, 

 with dissolved oxygen falling below 1 mg- 1"^ and, in specific regions, to 0.0 mg 1'^ (CT 

 DEP 1997). Hypoxia is a direct result of eutrophication, the excessive nutrient loading and 

 organic matter enrichment of the estuarine waters of Long Island Sound. The increased 

 input of nitrogen concentrations from terrestrial sources results in artificially abundant 

 phytoplanktonic populations. As the excessive organic matter settles and decomposes on the 

 seafloor, the greatest depletion of oxygen occurs in the bottom waters, which may become 

 anoxic at depth. The problem is exacerbated in the late summer by the stratification of the 

 Sound waters into two separate layers, with a warm layer over cool, denser waters. 

 Because limited mixing occurs, the bottom waters do not become reoxygenated by 

 photosynthesis and wave action which supply oxygen to the surface waters. 



The Long Island Sound Study (LISS), a U.S. Environmental Protection Agency 

 (EPA) management program, officially recognizes the onset of hypoxia at DO 

 concentrations below 3.0 mg 1"' (LISS 1990, CT DEP 1997). In experimental tests, DO 

 concentrations at 5.0 mg 1"^ or greater had few adverse effects on marine life (LISS 1990). 

 Concentrations of DO below 5.0 mg T' have been shown to reduce survival of some 

 planktonic larvae and growth of a variety of organisms, and DO concentrations below 3.0 

 mg r' tend to have more severe effects on marine life. 



Monitoring Cruise at the WLIS Disposal Site, September 1997 and March 1998 



