August 1985. Moreover, in June 1985, reduced sediments were 

 evident at the interface throughout the FVP mound. This recent, 

 widespread appearance of highly reduced sediments near the 

 sediment-water interface indicated these sediments were potentially- 

 being redistributed about the seafloor either by bottom currents 

 (unlikely given past current meter measurements) or other 

 disturbance factors (e.g., trawling, megafaunal bioturbation) . The 

 extremely patchy nature of this reduced material, both within an 

 image and between images, suggests a biological cause. It is 

 difficult to envision a physical disturbance mechanism which would 

 produce such a distribution of reduced materials. Conversely, 

 biological activity, such as decapod foraging and burrow 

 excavation, could easily result in the upward movement of isolated 

 clumps of highly reduced subsurface sediments. 



The boundary roughness (the vertical range of small-scale 

 topographic relief observed in the REMOTS® images) frequency 

 distribution (Figure 3-14) displayed a modal value of 0.4 cm 

 (reduced from 0.8 cm in August 1983). This is attributed to the 

 progressive "smoothing" of the surface both by currents and 

 biogenic reworking. Similar decreases in small-scale boundary 

 roughness have been noted at other DAMOS sites following disposal 

 operations. 



The frequency distribution of apparent Redox Potential 

 Discontinuity (RPD) depths (a measure of the apparent depth of 

 aerobic sediment which is indicative of bioturbation activity, 

 Figure 3-14) indicated the majority of RPD values fell within a 

 range of 2 to 5 cm. In the last REMOTS® survey (September 1984) , 

 the distribution exhibited a distinct major mode centered at 4.0 

 cm. The shallowest RPD depths during this survey were found at 

 station CTR (Figure 3-15) . Much of the variation in the RPD values 

 seen in the frequency distribution was the result of within-station 

 variability rather than between-station variability, due to the 

 presence of the near-surface patches of reduced sediment in many 

 images. 



The mean RPD depth at STNH-N (3.98) and all the CLIS 

 disposal mounds was deeper than at the CLIS-REF station (2.8 cm). 

 The exact reason for the anomalously thin apparent redox at the 

 CLIS-REF station is unknown. However, in the June 1985 survey of 

 the FVP Mound, the CLIS-REF station showed a distinct successional 

 "retrograde" conditioD with a progressive loss of Stage III 

 infauna. One possible mechanism for this is the intensive sediment 

 and benthic sampling that has been done at this location by the EPA 

 Narragansett Environmental Research Laboratory since 1982. 



Based on the theory that organism-sediment interactions 

 follow a predictable sequence after a major seafloor perturbation, 

 the designation of successional stage from REMOTS® image analysis 

 indicates the functional group of infauna present at any particular 



