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4.3 CLIS Reference Areas 



Reference area data are collected to provide a baseline against which results from 

 the dredged material mounds are compared. The majority of the July 1996 REMOTS® 

 results for the CLIS 95, CLIS 94, and NHAV 93 mounds were found to be analogous to 

 the conditions found at the three CLIS reference areas. Although the majority of the 

 REMOTS® photographs collected over the project mounds documented improving 

 conditions relative to previous surveys, limited signs of habitat degradation were apparent. 

 Replicate photographs collected at Stations lOON and lOOS over the CLIS 94 mound, as 

 well as Station 200N over NHAV 93, discovered conditions indicative of a low DO 

 environment. However, the decline in habitat quality at these stations may also be 

 attributed to a high SOD within the surface sediments caused by oxidation of labile 

 organics and gradually decreasing DO concentrations, rather than a hypoxic event (DO 

 concentrations <3.0 mg-1-1) in the bottom waters. Barring a dramatic benthic dismrbance, 

 complete recovery should be achieved within the next few years. Therefore, continued 

 REMOTS® sediment-profile photography over CLIS 95, CLIS 94, and NHAV 93 is 

 recommended for the 1997 monitoring effort, and periodically thereafter. 



Throughout the 19-year history of the DAMOS Program, CLIS-REF has been 

 utilized as a control area, representative of the ambient sediments of central Long Island 

 Sound. Located approximately 4.5 km southeast of the center of CLIS, this area should be 

 free of the effects of dredged material disposal and display the characteristics of an 

 undismrbed seafloor. On occasion, anomalous benthic conditions are detected at the CLIS 

 reference areas due to namral or anthropogenic effects. Benthic disturbances due to 

 hypoxia and commercial fishing activity have been documented within CLIS reference 

 areas in past years. 



As part of standard benthic community assessment techniques, the July 1996 

 REMOTS® survey required random selection of several sediment-profile photography 

 stations within a 300 m radius of CLIS-REF. One replicate photograph collected from 

 STA 9 revealed a pocket of dark, anoxic sediment approximately 5 cm below the sediment 

 water interface (Figure 4-4 A). A thin nepheloid layer of loose silt and clay, expelled from 

 a void in the subsurface sediments by the bisecting action of the REMOTS® camera, is 

 visible at the sediment- water interface as well as within the water column. The remaining 

 two replicates obtained from STA 9 displayed conditions indicative of an undisturbed 

 ambient bottom, suggesting a highly localized dismrbance (Figure 4-4B). Although 

 physical dismrbances can be attributed to a wide variety of sources (infaunal burrowing, 

 boat anchors, trawling scars, etc.) the presence of low reflectance, sulphidic sediment is 

 often used as an indicator of dredged material deposition. 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1996 



