45 



3.5 CLIS Reference Areas 



Complete REMOTS® results for the CLIS reference areas (2500W, 4500E, and 

 CLIS-REF) are available in Appendix E. Reference area data are collected to provide a 

 baseline against which results from the dredged material mounds are compared. CLIS- 

 REF has been a reference area for CLIS since the beginning of the DAMOS Program. 

 The two newer reference areas, 2500W and 4500E, have been monitored since 

 approximately 1987. 



3.5.1 Sediment Grain Size and Stratigraphy 



Physical indicators of the benthic environment include the grain size and boundary 

 roughness of the sediment surface. The major modal grain size was > 4 phi in all 

 reference station replicates indicative of ambient Long Island Sound sediments. Replicate- 

 averaged camera penetration ranged from 10.59 cm to 14.26 cm (Appendix A, Table 3-4). 

 Boundary roughness values ranged from 0.32 cm to 2.36 cm. Surface disturbance 

 determinations of biogenic processes, physical disturbance, and "unidentifiable" were 

 represented and equally distributed among the 39 replicates. 



In contrast to the other reference area photographs, one replicate image obtained 

 from Station 9 at CLIS-REF displayed an anomalous pocket of low reflectance, fine- 

 grained material approximately 5 cm below the sediment- water interface. In addition, the 

 surface sediment layers in this replicate photograph indicated a recent physical disturbance. 

 However, the lack of similar conditions in the remaining two replicates suggests this is a 

 localized benthic disturbance. 



Redox rebound intervals were identified in several reference area photographs, 

 indicating a change in water column dissolved oxygen concentrations. No methane gas 

 was detected in the subsurface sediments of the CLIS reference areas, but one replicate 

 photograph collected at 2500W was classified as low DO. 



3.5.2 Benthic Community Assessment 



Replicate-averaged RPDs at all three reference areas ranged from L5 cm to 

 2.62 cm. These levels indicate healthy benthic conditions and an improvement relative to 

 the September 1995 REMOTS® survey. 



The successional stage status at all reference stations was most commonly Stage I on 

 Stage III, indicating a mature benthic assemblage. Stage II individuals were not identified 

 in any replicate REMOTS® image. Median OSIs at the reference areas consistently ranged 



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



