38 



photographs at 2000W did not provide evidence of low dissolved oxygen concentrations in 

 the sediment pore waters or the overlying water column. Station W300E (within 2000W) 

 revealed high SOD material and poorly developed RPD layers (Figure 3-19). In addition, 

 methane gas bubbles and dark subsurface sediments at Station W100E provided some 

 evidence of either historic depositional events, earlier periods of low oxygen, or both (Figure 

 3-19). 



RPD boundary layers were difficult to distinguish in some replicate photographs at the 

 SOUTH reference area due to the moderate-to-high reflectance of the subsurface sediments. 

 Some sediment profiles showed patchy, subsurface relic RPD layers. The reconnaissance 

 REMOTS® photographs taken at the center of the EAST reference area showed homogeneous 

 sediment profiles with moderately developed RPD boundary layers; however, REMOTS® 

 photographs from other EAST reference area stations showed patchy and/or relict RPD 

 layers. 



3.2.5 Succession al Stage 



Exclusively Stage I infaunal activity was evident at six of the 25 WLIS "F" 

 REMOTS® stations (Figure 3-20). Four of these six stations were clustered within 100 m of 

 the center of the WLIS "F" mound. REMOTS® photographs from each of these stations 

 revealed extensive reworking of the top several centimeters of sediment by these pioneering 

 Stage I infauna, indicating that the initial phases of recolonization were in progress. 



At least one replicate photograph from each of the remaining WLIS "F" stations 

 (400N was indeterminate) displayed evidence of Stage III infaunal activity (i.e., active 

 feeding voids, see Figure 3-8/4). Five of these stations were within 100 m of the WLIS "F" 

 center. The presence of these Stage III organisms indicated that the newly deposited 

 sediments were rapidly recolonized and that incorporation of the deposited material into the 

 ambient sediment matrix can be expected to proceed rapidly. 



Photographs from ten of the 39 reference area REMOTS® stations showed exclusively 

 Stage I infaunal activity. Five of these stations were located within the SOUTH reference 

 area. During the 1990 and 1991 monitoring surveys at WLIS, the southern reference area 

 (2000S) contained the greatest proportion of stations exhibiting only Stage I infaunal activity. 

 The remaining reference area REMOTS® stations contained Stage III or combinations of 

 Stage I and Stage III seres. 



3.2.6 Organism-Sediment Index (OSI) 



The median OSI values for 24 WLIS "F" stations ranged from +1.5 to 9. Organism- 

 Sediment Index values for Station F400N could not be determined due to overpenetration of 

 the REMOTS® camera. The unimodal frequency distribution of median OSI values had a 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1992 



