relatively thin RPD values and the presence of methane at three 

 station replicates. In addition, despite the apparent increase in 

 colonization by Stage III taxa, the majority of photographs (69%) 

 showed Stage I seres as predominant. The two low indices at station 

 600N (-1 and -3; Figure 3-57) are apparently related to local surface 

 disturbance (Figure 3-58) . 



The major change in the MQR mound in 1986 relative to 1985 

 was the appearance of Stage III seres at most stations (13 out of 17) . 

 This was significant because the MQR disposal mound has historically 

 experienced the slowest rate of colonization compared with other CLIS 

 disposal mounds. It is unclear if the appearance of Stage III taxa 

 represents larval colonization or passive transport of adults from the 

 surrounding seafloor related to the passage of Hurricane Gloria in 

 September 1985. Because well-developed feeding voids take several 

 weeks to months to be produced by head-down deposit feeders, the post- 

 hurricane survey of the MQR mound in October may have missed the 

 evidence of their presence. 



The mean apparent RPD depth appears to be significantly 

 shallower in 1986 than in 1985. This may be related to developing 

 hypoxia in Central Long Island Sound. In August 1986, a dissolved 

 oxygen survey of the central Sound was conducted for EPA Region I by 

 SAIC (SAIC, 1987) . As part of this study, five polarigraphic 

 electrode (YSI) measurements were made of dissolved oxygen at station 

 Center at the MQR mound at a distance of one centimeter above the 

 bottom. These values were 3.38, 2.42, 2.60, 2.60, and 2.56 mg/1. 

 Five measurements were also obtained from the CLIS reference station 

 on the same day (3.28, 2.60, 2.54, 2.46, 2.46 mg/1). All these values 

 were within the hypoxic range and represent concentrations of less 

 than half saturation. These data strongly suggest that dissolved 

 oxygen concentrations should be measured routinely in all Long Island 

 Sound DAMOS monitoring efforts in order to understand the year-to- 

 year changes which are mapped with the REMOTS® system. The MQR mound 

 still continues to lag behind the other disposal mounds in terms of 

 infaunal colonization and sediment irrigation. 



3.3.6 Norwalk (NOR) Mound 



The major grain-size mode of silt-clay (> 4 phi) remained 

 unchanged at all stations from previous surveys. Most stations showed 

 the presence of very fine, fine, and medium sand (in the 4-1 phi 

 range) overlying disposed muds (Figure 3-59) . Several stations also 

 showed the presence of shell-lag deposits, and methane gas was present 

 at station Center (Figure 3-59) . Disposed material was apparent at 

 stations near the center of the grid (Figure 3-59) . In the August 

 1985 survey, over half of the station replicates showed evidence of 

 reduced sediment at the surface; this was attributed to biogenic 

 activity. The present survey did not reveal extensive surface 

 deposits of reduced sediment. An exception to this was station 200W 

 (Figure 3-60) , where low reflectance sediment had filled-in a 



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