43 



4.2 Recoionization Status at WLIS 



In addition to determining the areal distribution of dredged materials, the REMOTS® 

 sediment-profile survey was conducted to assess the extent of infaunal recoionization at the 

 active disposal point. Approximately 90% of the WLIS on-site stations showed the presence 

 of Stage III infauna. This result exceeds our prediction that most of the WLIS "E" mound 

 would be in a Stage I condition. Such rapid colonization probably reflects the survival of 

 Stage III taxa buried by a blanket of disposed material spread over WLIS "E". Rapid 

 catastrophic burial of burrowing infauna does not always result in death (Goldring 1964, 

 Kranz 1974, Maurer et al. 1978). Each taxon has a "critical overburden" thickness. If the 

 layer of dredged material is less than this overburden thickness, the infauna will initiate an 

 escape burrowing response and move upward through the sediment to reestablish a 

 connection with the new sediment- water interface. Another mechanism of rapid adult 

 colonization of newly deposited dredged materials can take place by immigration, for 

 example, by swimming stages of the polychaete Nephtys incisa (Rhoads et al. 1977). 

 Because disposal took place during a period of low water temperatures (November to May, 

 1991), recoionization of WLIS "E" likely involved a nonlarval mode of recoionization. The 

 Stage III stams of the WLIS "E" and WLIS "D" grids indicates that dismrbances relating to 

 dredged material disposal were primarily physical and relatively short-lived. 



As noted during the 1990 survey, the 1991 OSI values of < +6 were clustered 

 primarily at stations west of the active disposal point. Most likely, this clustering of low OSI 

 stations reflects those areas where the most recent dredged material disposal had occurred. 

 Given the rapid recoionization and predominance of Stage HI infauna observed throughout 

 much of the WLIS Disposal Site, we expect the continued development (deepening) of the 

 RPD layer and subsequent increase in the OSI value at these stations. 



Several stations near WUS "A" (E400W) and WLIS "D" (D200W, D200N, DIOOS, 

 and D300S) that had low (< +6) OSI values in the 1991 survey continued to exhibit low 

 OSI values in the 1991 survey. Closer examination of the REMOTS® photographs fi-om 

 these stations revealed extremely dark subsurface sediments characteristic of high 

 concentrations of labile organic material and sulphides. From this observation, we infer high 

 sediment oxygen demand (SOD) at these stations. Stage HI infaunal activity was evident at 

 five of these six stations; however, the DAMOS tiered monitoring strategy (Germano et al. 

 1994) views persistence of low reflectance sediment near the surface as a potentially adverse 

 habitat condition resulting from anthropogenic activity. According to the tiered approach, 

 "...even if (investigators) have not defined the precise line at which a non-adverse condition 

 becomes an adverse condition, the inherent assimiption (of the tiered approach) was that we 

 could monitor for changes in the necessary precursors that eventually would lead to an 

 adverse impact" (Germano et al. 1994). In this instance, future monitoring efforts should 

 include sediment grab sampling and bulk sediment contaminant level analyses and/or bioassay 

 testing. Given the results of these analyses, "a manageable and interpretable monitoring plan 



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



