water temperatures, a stratified water column, and high rates of 
benthic metabolism (high BOD and COD). This August Effect has been 
documented for sub-estuaries of Long Island Sound such as New Haven 
Harbor and Bridgeport Harbor but has not been observed at the NLON 
Disposal Site. Further evidence of hypoxic bottom conditions 
occurred when SAIC scientists on board the research vessel observed 
dense aggregations of the amphipod Ampelisca swimming at the 
air/water interface. Amphipods only leave the bottom and their 
tubes to exhibit this type of behavior when there is severe low 
dissolved oxygen stress in bottom waters. This seasonal stress 
factor may have a major influence on the recolonization of disposal 
mounds at the New London Disposal Site. 
The RPD values greater than 3 cm were located in two 
large patches in the center of the disposal site (Figure 3-14) and 
included the disposal mounds themselves. These patches were 
elongated in a NE-SW direction. This pattern may be related to the 
region's bathymetric gradients and bottom current regime (see 
Figure 3-1). 
Much of the site was dominated by an extensive mat of 
tubicolous amphipods (Ampelisca sp., indicated as Stage II in 
Figure 3-15). Many of these tube mats appeared disturbed; the tube 
mats were rolled up into mud clasts. Other mats showed evidence 
of decomposition of the tubes, apparently related to death of the 
amphipods and subsequent microbial decay of the binding organic 
matrices (Figure 3-16). These features indicated a retrograde 
Stage II sere. In many cases, this retrograde status was likely 
related to the apparent low bottom-water oxygen levels. 
Conversely, some photographs showed apparently healthy Stage II 
tube mats (Figure 3-17). The largest area of viable amphipods fell 
within that area of the bottom where apparent RPD depths were 
greater than 3 cm which again included the areas of the disposal 
mounds. 
Most of the region also exhibited evidence of Stage III 
infauna (Figure 3-15). When these deep-dwelling, head-down feeders 
were clearly evident below the Stage II mats, the successional 
stage was classified as a Stage II on III (indicated by the symbol 
III-II in Figure 3-15). Alternatively, some photographs revealed 
less definitive evidence of Stage III infauna (Figure 3-18). These 
were considered transitional between Stage II and III and were 
symbolized by a II--III in Figure 3-15. The areas which lacked any 
evidence of Stage III infauna (hatched areas in Figure 3-15) were 
largely restricted to the borders of the survey area and, in 
general, overlapped the regions of suspected hypoxic bottom water 
conditions. 
In addition to infauna, the surface of several stations 
exhibited hydroids and/or large disarticulated bivalve shells 
which, in turn, served as a surface for the attachment of 
19 
