20 



amphipods are common in eastern Long Island Sound. The presence of dense aggregations 

 of these amphipods (Ampelisca sp.) in the area surrounding NLDS has been identified as a 

 cyclical phenomenon as the spring-summer and over-winter populations mature, reproduce, 

 and decline. As a result, the timing of the individual REMOTS® surveys over the years have 

 documented the amphipod populations in eastern Long Island Sound during different stages 

 of the life cycle. 



Stage HI biota represent a high-order successional stage and are usually associated 

 with areas of seafloor that are not usually subject to surface disturbances. Stage HI 

 assemblages (infaunal invertebrates) are typically head-down deposit feeders whose feeding 

 behavior usually results in distinctive subsurface voids. The foraging activities of Stage m 

 organisms are capable of introducing oxygen-rich bottom water to the sediment at depths 

 approaching 10-20 cm below the sediment- water interface. As a result, the bioturbational 

 activity of Stage HI organisms tends to cause the deepening of the RPD. 



A multi-parameter REMOTS® Organism-Sediment Index (OSI) has been constructed 

 to characterize habitat quality (Table 2-3). Habitat quality is defined relative to two end- 

 member standards. The lowest value is given to those sediments that have low or no 

 dissolved oxygen in the overlying bottom water, very shallow RPD depth, no apparent 

 macrofaunal life, and methane gas present in the sediment. The REMOTS® OSI value for 

 such a condition is minus 10 (-10). At the other end of the scale, an aerobic bottom with a 

 deep RPD, evidence of a mature macrofaunal assemblage, and no apparent methane gas 

 bubbles at depth will have an OSI value of plus 11 (+11). OSI values of +6 or less are 

 indicative of chronically stressed benthic habitats and/or those that have experienced recent 

 disturbance (i.e., erosion, sediment transport, dredged material disposal, hypoxia, intense 

 demersal predator foraging, etc.; Rhoads and Germano 1982). 



2.2.1 Seawolf Disposal Mound 



The Seawolf Mound was first examined with the use of sediment-profile photography 

 in September 1997. A 29-station REMOTS® sampling grid centered at 41° 16.456' N, 

 72°04.863'W was established over the disposal mound, based on the reported size and 

 morphology of the bottom feature upon completion of capping operations. Four stations 

 were established at distances of 75 m, 150 m, 300 m, and 450 m along each of seven arms 

 radiating from the center station (Figure 2-3; Table 2-4). The follow-on survey performed in 

 July 1998 occupied the same station grid to facilitate comparisons with the 1997 data set. 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



