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5.0 CONCLUSIONS 



Based on the results of the REMOTS® and precision bathymetric surveys, an 

 accumulation of recently-deposited dredged material occurred where the disposal 

 buoy had been located during the 1989 -1990 disposal season. The deposited 

 material accumulated around the buoy in a broad, circular mound up to 5.3 m thick 

 and had an average radius of approximately 225 m. Mound heights at the "A" and 

 "C" mounds decreased slightly since the previous survey in July 1988, whereas the 

 height of the WLIS "B" mound (the 1986 - 1987 and 1987 - 1988 active disposal point) 

 decreased 1.0 m. Most likely, a combination of sediment compaction and 

 bathymetric analysis limitations inherent to steep-sloped topographies accounts for 

 the observed changes. No evidence, as observed with REMOTS® photography, exists 

 to suggest significant erosion had occurred. Consistent with the results of the July 

 1988 survey, relic dredged material was visible in REMOTS® photographs from 

 stations on and near the WLIS "A", "B", and "C" mounds. 



REMOTS® parameters of OSI and RPD were significantly different between 

 reference and disposal site stations, reflecting the recent disturbance in the benthic 

 environment due to disposal activities. An on-site median OSI of +7 combined with 

 the development of a deep RPD and Stage III infaunal recolonization at the center of 

 the disposal mound indicated that the disturbance was primarily physical in nature. 

 Reference station OSI and RPD values showed little change from the 1988 survey, 

 indicating that a relatively healthy and stable benthic habitat persisted. Although 

 direct statistical comparisons of the 1988 and 1990 on-site data could not be 

 performed due to dramatically different sampling designs, the July 1990 results 

 indicated a continued trend of improving benthic habitat conditions as observed 

 during the 1987 and 1988 WLIS studies (SAIC, 1990a,b). 



Conditions observed in REMOTS® photographs (e.g., a steady increase in both 

 the apparent RPD depth and the progress of infaunal recolonization) did not provide 

 evidence of stress related to near-bottom hypoxia. Near-bottom DO concentrations, 

 although significantly less than near-surface concentrations, were within the aerobic 

 range. Such decreases in DO concentration with water depth are typically found in 

 conjunction with a highly stratified water column (as seen in the CTD profiles of 

 selected stations in the area). Although intensified thermal stratification could foster 

 near-bottom hypoxic conditions, no evidence of the effects of low dissolved oxygen 

 levels was apparent in the 1990 REMOTS® photographs. 



The results of the 1990 REMOTS® survey support evidence from earlier 

 studies that conditions at WLIS are returning to the relatively undisturbed 

 conditions seen during the August 1985 REMOTS® survey (SAIC, 1988a), prior to 

 both Hurricane Gloria in September 1985 and the severe hypoxia which occurred in 

 western Long Island Sound in the summer of 1986. The improved conditions in this 

 region of the Sound have been attributed to the absence of severe hypoxic stress in 

 recent years; therefore, the condition of the benthic environment at the WLIS 



Monitoring Cruise at the Western Long Island Sound Disposal Site 



