between the November 1987 and July 1988 surveys. The patchy RPD 

 layers which existed at many stations may have been a direct 

 consequence of the sediment-reworking activities of Stage III 

 organisms. It appears that the reduced sediments which typically 

 extended to the surface in many of the photos (see Figure 3-13) were 

 transported from deeper zones as a result of burrowing and/ or 

 "conveyor-belt" feeding by the larger infauna. 



4.3 CTD and Dissolved Oxygen Sampling 



The objective of the CTD/DO sampling at WLIS was to assess 

 near-bottom dissolved oxygen concentrations in relation to benthic 

 habitat conditions at and in the vicinity of the site. As 

 indicated, the REMOTS® results suggested that relatively healthy 

 benthic conditions existed at the time of sampling, although 

 near-bottom dissolved oxygen concentrations at both the disposal 

 and reference sites were near the hypoxic range (Table 4-1) . The 

 strong thermal stratification of the water column apparent in the 

 CTD profiles most likely contributed to the observed vertical 

 distribution of DO. Past experience has shown that in Long Island 

 Sound, the lack of mixing associated with a strong and persistent 

 pycnocline during the warmer summer months can exacerbate oxygen 

 depletion in near-bottom waters. Furthermore, the solubility of 

 oxygen in seawater declines as water temperature and salinity 

 increase (Weiss, 1970) . Dissolved oxygen concentrations remained 

 at or close to saturation in the surface waters and were slightly 

 higher at reference stations 2000W and 2000S. This reflected the 

 normal spatial and temporal variability in near-surface DO which 

 might be expected in any estuarine area over a 6 to 8 hour sampling 

 period. 



The relatively healthy benthic conditions at WLIS as seen 

 in the REMOTS® photos suggest a general absence of stress which 

 might otherwise be attributed to near-bottom hypoxia in the weeks 

 and months preceding the survey. On a larger time scale, it was 

 found that seasonal hypoxia was not as severe or widespread in Long 

 Island Sound in the summer of 1987 compared to the preceding year 

 (SAIC, 1988) . This might help to explain the continued improvement 

 in benthic conditions noted at WLIS in 1987 and 1988, as well as the 

 generally healthy conditions noted at the other Long Island Sound 

 disposal sites (CLIS and NLON) in 1987. Conditions observed at WLIS 

 in July 1988 may still have represented the "pre-hypoxic" condition 

 in this region of the Sound, with the possibility that hypoxia 

 developed later in the summer with attendant adverse sediment 

 effects. However, the dramatic change in both the high reflectance 

 of the oxidized sediment layers in the REMOTS® photos and the 

 increased region-wide appearance of Stage III infauna as compared 

 with results from 2-4 years ago lend increasing support to our 

 conclusions from earlier studies that the stressed conditions noted 

 earlier were unrelated to disposal but resulted from region-wide 

 hypoxia or, in 1985, physical seafloor disturbance due to the 



9 



