U3_ 



The dominant organism at Station 300SE (mound apron), Monticellina baptisteae, is 

 a Stage I cirratulid polychaete. A relatively low density of M. ambiseta (Stage I) also was 

 present, along with Stage II amphipods (A. vadorwn) and a small range in shell length sizes 

 of Stage II N. annulata (0.75 to 2.0 mm). Two REMOTS® replicates provided useful 

 information; both showed this station to be a Stage II assemblage. This conclusion is 

 supported by the ground-truth samples. The presence of six relatively large specimens of the 

 bivalves Pitar morrhuana, Astarte undata, and Anadara transversa, along with Stage III 

 Lumbrinerid polychaete Scoletema hebes, further suggested that this station had not 

 experienced a great deal of disturbance in the recent past. The relatively large body size of 

 the bivalves (biomass) indicates that they have occupied this station for more than one year; 

 from a functional perspective they are considered Stage HI organisms. However, the 

 REMOTS® successional designation failed to acknowledge the presence of these larger- 

 bodied Stage HI organisms. 



Overall, comparison of the grab sample faunal data with successional stage 

 interpretation from REMOTS® images shows that the Seawolf Disposal Mound was 

 predominantly in a Stage II assemblage based on the numerical dominance of Nucula 

 annulata and tubicolous amphipods. Stage I taxa were also present (spionid and capitellid 

 polychaetes), but in lower abundance than is typically found in the earliest pioneering 

 assemblage. Undisturbed Stage HI species (e.g., large bivalves) were encountered at one 

 station (300SE) on the thin apron of the Seawolf Mound. Small numbers of Stage HI 

 polychaetes were found at all of the stations, but because of their low densities, they were 

 largely undetected in the sediment profile images. 



The importance of N. annulata in intermediate stage colonization at this site is a 

 relatively new observation. While N. annulata are commonly found as members of Stage HI 

 deposit-feeding communities in soft mud, this is only the third time that this species has been 

 noted as playing an important role in colonization of sandy to muddy dredged material. 

 Sediment-profile imagery is unlikely to allow identification of very small N. annulata, but 

 REMOTS® data from the N. Y. Mud Dump Site did allow identification of abundant 

 populations of large mature specimens of Nucula spp. (Valente 1998). 



4.2.2.3 Spatial Trends in Faunal Diversity and Abundance 



As previously indicated, the benthic sampling stations were located in three distinct 

 topographic areas of the capped mound: mound apex (CTR, 75E); mound plateau (150W, 

 150N, 300WSW); and mound apron (300SE) (Figure 2-5). The Seawolf Mound lacked a 

 large area with steep mound slopes and could be best characterized as a broad flat mound 

 with a small apex. The apron areas consisted of thin deposits of dredged material (usually 

 less than 10 cm) that typically cause minimal disturbance to the benthic community. 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



