14 



shallowest RPD depth measured was 0.73 cm, and the deepest was 4.76 cm (Figure 3-5). 

 Because of shallow camera penetration, the RPD was deeper than penetration and could 

 not be measured in 11 photographs. Of these eleven photographs, prism penetration 

 ranged from 0.5 to 2 cm in 4 photographs, 2 to 3 cm in 6 photographs, and greater than 

 8 cm in one photograph. 



3.1.4 Successional Stage 



Sediments at BLDS contained a relatively robust benthic community. Infaunal 

 communities were dominated by the Stage II-on-Stage III class. Surface sediments at all 

 stations were populated by stick-building amphipods (Family Podocerdiae; Figure 3-6, A). 

 Sedentary polychaete tubes extended above the sediment-water interface at varying 

 densities throughout the study area (Figure 3-6, B). Below the surface Stage II 

 community, evidence of an abundant Stage III community was commonly observed as 

 burrowing polychaetes (Figures 3-3 and 3-2, B) and/or subsurface feeding voids (Figure 3- 

 7). Pelletized sediments, indicative of actively feeding infauna, were found near the 

 sediment- water interface as well as inside feeding voids. Infaunal species were not limited 

 to polychaetes; a bioturbating caudate holothurian Molpadia oolitica was photographed at 

 C2-10 (Figure 3-8). In addition to infaunal species, several epifaunal species were 

 observed including large mud anemones, hydroids, and bryozoans. 



3.1.5 Organism-Sediment Index 



The REMOTS® Organism-Sediment Index (OSI) is a multiparameter tool used to 

 evaluate the interaction of infauna and the sediment in which they live. OSI values can 

 range between -10 and + 1 1 and are based on RPD depth, successional stage, and the 

 presence of methane associated with anoxic sediments. As there was no indication of low 

 oxygen conditions, OSI values from BLDS were a function of RPD depth and successional 

 stage. Values ranged from a minimum station mean of 5 to a maximum station mean of 10 

 (Appendix). Mean transect OSI values ranged from 6 to 9 (Figure 3-9). OSI values >6 

 are indicative of relatively healthy sediments. OSI values could not be calculated for 

 twelve photographs: eleven due to indeterminate RPD depths, and one (replicate CI -7a) 

 due to indeterminate successional stage. (The plan view photograph for replicate CI -7a 

 shows the camera frame resting on a rock, restricting penetration.) 



3.2 Plan View Photography 



The plan view photographs provided useful information about surface sediment 

 characteristics which were not always discernible from the REMOTS® photographs. 

 Surface sediments at BLDS were composed primarily of silts and sands (Figure 3-10). 



Monitoring Cruise at the Historic Boston Lightship Disposal Site, August 1994 



