50 



penetration ranged from 12.86 cm to full penetration (20 cm), generally increasing towards 

 the center of the mound, except at the center station (14.47 cm; Appendix A: Table 3-3). 

 In general, the lower camera penetration values correlated with the highest surface 

 disturbance values; values > 1 cm occurred at 200S, 300E, 300N, 300W, and CTR. The 

 primary cause of surface disturbance over the CLIS 1994 mound was biogenic activity. 



3.2.2.2 Benthic Community Assessment 



The replicate-averaged mean Redox Potential Discontinuity (RPD) values ranged 

 from 0.46 cm at CTR to 4.03 cm at 300S (Figure 3-24). A gradient of RPDs increased 

 from the center out towards the edges of the mound, ranging from approximately 0.5 cm at 

 CTR, to 1.5 cm at 100 m, to 2-4 cm at 300 m. The overall average RPD value for the 

 mound was 1.76 cm, despite indications of low dissolved oxygen resulting from hypoxic 

 conditions within the bottom waters over many REMOTS® sediment-profile photography 

 stations (100W, 200S, 200W, 300E, 300N, 300S, 300W). 



No methane was noted in any photograph obtained on the surface of the CLIS 94 

 mound. However, the RPD depths varied among replicates of the same station, indicating 

 a patchy benthic environment. Replicate A at Station 300S exhibits a mean RPD depth of 

 5.87 cm indicative of a healthy benthic environment (Figure 3-25 A). Conversely, replicate 

 B of Station 300S displays a shallow RPD and indications of low dissolved oxygen (Figure 

 3-25B). 



The successional stage status was relatively advanced for Station 300S and the 

 remainder of the CLIS 94 mound as an area recently impacted by dredged material 

 (Germano et al. 1994). Station 100W was the only station without evidence of Stage III 

 organisms in any of the replicates (Figure 3-26). The most common stages noted in the 

 replicate photographs were Stage I and Stage I on III. Median Organism-Sediment Index 

 (OSI) values of the replicates ranged from -1 at 200S (low RPD, low DO) to 9 at 200N. 

 Low OSIs ( < 6) are concentrated along the western and southern arms of the grid 

 primarily due to the indication of a low dissolved oxygen event (Figure 3-24). 



3.3 FVP Mound 



The experimental FVP mound, located in the far northeast quadrant of CLIS, was 

 monitored extensively as part of the Field Verification Program during the 1980s. 

 Historically, benthic infaunal communities inhabiting the FVP sediments have been more 

 susceptible to benthic disturbances, relative to other CLIS mounds. Composed of 

 uncapped UDM deposited in 1983, the FVP mound continues to be periodically monitored 

 as part of the DAMOS Program. No bathymetric data were collected over the historic 



Monitoring Cruise at the Central Long Island Sound Disposal Site, September 1995 



