68 



September (Figure 4-6). The slides were reanalyzed in some cases to determine whether 

 images indicated redox rebounds, relic RPDs, or dredged material layering due to multiple 

 disposals of barge loads at the buoy location during one disposal season. 



4.1.4 Summary of Benthic Conditions at H and I Mounds 



The H mound has been successfully recolonized supporting a benthic community 

 with an advanced successional status. Formed during the 1995-1996 disposal season, the 

 H mound was observed in the 1996 REMOTS® survey to have a solid Stage I pioneering 

 polychaete community with some evidence of Stage III activity. Stage II activity is not 

 typical in the western Long Island Sound region. In the September 1997 REMOTS® 

 survey, we again observed a predominance of Stage I surface tube dwellers with an 

 increase in the number of replicates with Stage III feeding voids. However, the RPDs 

 were decreased from the July survey. By March 1998, feeding voids were apparent in 

 almost every replicate indicating a healthy Stage III community over the H mound. 

 Deposit feeders are known to survive over the winter months, whereas shallow-living 

 organisms have a higher mortality in the winter months (Rhoads et al. 1977). Although 

 Stage I organisms were present in March, they were less abundant. Layering of dredged 

 material disposed during the 1995-1996 disposal season was apparent in many images. 

 Redox rebounds were less apparent and shallower in March than September. Because 

 metabolic rates are depressed in the colder winter months, the correlated depth of oxidation 

 tends to decrease. However, the RPD depths were greater in March, which indicates that 

 the sediments were affected by hypoxia in September. Decomposition of organic matter is 

 greater in the summer and increases the sediment oxygen demand, whereas oxygen is 

 controlled by physical diffusional processes in the winter. 



The I mound, created during the 1996-97 disposal season, also indicated improved 

 conditions from September to March. However, the changes were less dramatic when only 

 the 5-grid stations were compared. RPD depths and OSI values were lower in the outside 

 stations which were notably at greater water depths. The successional status in September 

 was advanced for a recently deposited mound and continued to indicate a healthy recovery 

 in March. Figure 4-7 shows a lobster living at 150W and shrimp at 50S B on the disposal 

 mound. 



Although the I mound, the most recent deposit at WLIS, has not been placed 

 directly over an isolated problem area identified in the 1996 report, the apron of the mound 

 likely covers this region. Concern had been expressed over the slow recolonization rates at 

 Station D200S, to the east of the G mound, apparently due to low dissolved oxygen 

 conditions. I mound stations, 50W and 50S, close to D200S, indicated favorable benthic 

 conditions during both September and March surveys. 

 Monitoring Cruise at the WLIS Disposal Site, September 1997 and March 1998 



