26 



survey, sediment profiles from several stations within the WLIS-REF and 2000S reference 

 areas continued to exhibit relic or buried RPD layers indicative of past disposal operations 

 (Figure 3-14). REMOTS® photographs from stations within the 2000W reference area 

 exhibited uniform sediment profiles with well-developed RPD layers (mean apparent RPD 

 depth of 3.8 cm), with the exception of station W300S where variability among replicate 

 photographs (Figure 3-15) provided some evidence of past dismrbance (e.g., disposal 

 operations or trawling). 



3.2.5 Successional Stage 



REMOTS® photographs from approximately 90% of all disposal site stations (WLIS 

 "D" and WLIS "E" grids, N = 38) provided evidence of Stage HI infaunal activity (Figure 

 3-16). The majority of stations had combinations of Stage I on Stage III and Stage HI seres. 

 Several stations on, and adjacent to, the WLIS "E" mound have apparently experienced rapid 

 recolonization of the recently deposited dredged material by Stage III infauna as shown by 

 the presence of large feeding voids at depth (Figure 3-6B). Photographs from disposal site 

 stations (N = 4) exhibiting exclusively Stage I activity revealed extensive reworking of the 

 upper few centimeters of sediment by these pioneering infaima (Figure 3-17) indicating that 

 the initial phases of recolonization were in progress. Within the three reference areas, five 

 of thirty-nine stations exhibited exclusively Stage I infauna. Four of these five stations 

 (80%) occurred within the 2000S area. During the 1990 survey, six of thirty-nine stations 

 (three stations in the 2000S reference area) exhibited exclusively Stage I taxa. All other 

 reference area stations had combinations of Stage I, Stage HI, and/or Stage I on Stage HI 

 seres. 



3.2.6 Organism-Sediment Index (OSI) 



The Organism-Sediment Index (OSI), a multiparameter REMOTS® index 

 incorporating apparent RPD depth and infaunal successional stage, is useful in mapping 

 regions which have experienced dismrbance (i.e., dredged material disposal, trawling, etc.). 

 The frequency distribution of median OSI values for the WLIS "E" stations (Figure 3-18) 

 had a major mode of -1-8 (median of -1-7). Approximately 38% of the on-site stations had an 

 OSI of < -f-6, compared to 53% as noted during the 1990 survey. Based on the results of 

 past REMOTS® surveys, OSI values of < -f-6 are considered indicative of stressed benthic 

 habitats which have experienced recent dismrbance (i.e., erosion, dredged material disposal, 

 hypoxia, etc.; Rhoads and Germano 1986). Low OSI values in 1991 occurred primarily as a 

 small cluster of stations west of the active disposal point (Figure 3-19). Additionally, several 

 stations in the vicinity of the "A" mound (E400W) and WLIS "D" (D200W, D200N, DIOOS, 

 and D300S) continued to exhibit low OSI values durmg the 1991 survey. All but D300S 

 exhibited low OSI values in 1990. 



Monitoring Cruise at the Western Long Island Sound Disposal Site, June 1991 



