bottom hypoxic conditions had occurred at the WLIS site. Near-surface DO 

 concentrations were significantly greater than corresponding near-bottom values 

 (Table 3-1); however, this difference in concentration is most likely attributable to a 

 strong thermal stratification, as apparent in the CTD profiles. This stratification of 

 temperature and dissolved oxygen concentration are typical for the summer months 

 in this region of Long Island Sound (Welsh and Eller, 1991, and SAIC, 1987). 

 Differences in near-surface DO concentrations at the disposal site and the reference 

 areas were within the normal spatial and temporal ranges which might be expected 

 in any estuarine area over a 6 to 8 hour sampling period. 



The 1990 CTD profiles of temperature and salinity at the disposal and 

 reference areas were similar to CTD profiles collected in 1988, while near-bottom 

 dissolved oxygen concentrations exhibited a slight increase. The 1990 REMOTS® 

 and CTD/DO data provided evidence of the continuing improvement in the benthic 

 conditions observed in 1987 and 1988 following the severe and widespread hypoxia 

 reported in 1986 in Long Island Sound (SAIC, 1988a). Conditions observed at WLIS 

 in July 1990 may have represented the "prehypoxic" state in this region of Long 

 Island Sound; however, the overall condition of the benthic environment suggests 

 that any seasonal hypoxic occurrences prior to the July 1990 survey were not as 

 severe as reported in previous years. 



4.4 WLIS 3000 X 2500 Meter Bathymetric Survey 



Decreasing the lane spacing of the 3000 X 2500 m bathymetric survey from 

 200 to 50 m enhanced the resolution of the entire WLIS Disposal Site. Many of the 

 features observed in the 1982 survey (SAIC, 1982 and Figure 3-5) were readily 

 apparent in the 1990 survey, however, the improved detail of the 1990 survey 

 (Figure 3-6) will more adequately assist future disposal site management decisions. 



Monitoring Cruise at the Western Long Island Sound Disposal Site 



