1.0 Introduction 



As part of the current DAMOS monitoring program designed to assess benthic community structure of 

 disposal mounds in Long Island Sound, infaunal studies were planned that would permit comparison of 

 results obtained from analysis of grab samples with the corresponding REMOTS® data analyzed by SAIC. 

 Infaunal analyses were planned for six stations to be established on the Seawolf dredged material disposal 

 mound at the New London Disposal Site. The grab samples were to be collected on the same day that the 

 REMOTS® sediment-profile images were acquired. 



2.0 Methods 



At each of six stations, CENTER, 75E, 150N, 150W, 300SE, and 300WSW (named in reference to their 

 distance in meters and direction away from the center of the disposal mound), one grab sample for benthic 

 infauna was obtained with a 0.04-m 2 Ted Young grab. Upon retrieval, the benthic infaunal samples were 

 visually inspected for depth of the apparent RPD layer, sediment color and texture, and penetration depth 

 of the grab which gave an approximate sample volume. The samples were then washed into a bucket, 

 sieved through 500-um mesh screen, transferred into 1-1 wide-mouth plastic containers, and fixed in 10% 

 buffered formalin. After 48 h of fixation, the samples were resieved with fresh water, transferred to 70% 

 alcohol for preservation, and shipped to Cove Corporation for sorting and species identification. Most 

 identifications of small Crepidula and Ampelisca individuals were made by the author. For ease and 

 accuracy of sorting the samples were stained with Rose Bengal. 



Each taxon and its abundance for each sample was recorded electronically into a database. All raw data 

 were compiled in a QuattroPro spreadsheet in order of NODC codes (Appendix A). Total faunal 

 abundances and number of species were calculated for each station, the ten most abundant species were 

 determined for each station, and a species list was generated (Table 1). Juvenile and indeterminable 

 organisms were included in calculations of density, but were excluded from diversity analyses unless no 

 other species belonging to those taxa were present in the sample. 



Diversity was calculated as Shannon-Wiener index H' and the associated evenness J' and by the 

 rarefaction method (Sanders, 1968). The Shannon-Wiener index was calculated using the base log 2 ; for 

 the rarefaction, the number of individuals was set at defined points between 25 and 800. 



3.0 Results 



A total of 100 (70 good species, 16 species identified to unique genera or major group suitable for diversity 

 analysis, 5 species used selectively for diversity analyses, and 9 taxa unsuitable for use in diversity 

 analyses, e.g. Odostomia spp.) taxa were identified from the samples (Table 1). Of species consistently 

 used for all analyses nearly half were polychaetes (39 species); the remainder included amphipods (1 1 

 species), bivalves (12 species), gastropods (9 species), decapods (6 species), isopods (2 species), a mysid 

 (1 species), and small numbers of nemerteans, oligochaetes, phoronids, echinoderms, hemichordates, and 

 chordates that were treated as one taxon each. 



The total number of individuals sorted out of the 6 samples was 2,600. The station with the lowest faunal 

 abundance was the CENTER station, with only 50 individuals belonging to 17 taxa. Moving 75 m away 

 from the center, station 75E had 200 individuals belonging to 26 taxa. Nearly twice as many species were 

 found at stations 150 m (50 taxa at 150N and 46 taxa at 150W) away from the center as at 75 m away from 

 the center, although there was a two-fold difference in abundance at these two stations. Station 150N had 

 more than twice as many animals, mostly Nucula annulata (301 individuals), as station 150W. A few 

 more species were seen in the samples taken 300 m away from the mound center, 66 and 54 taxa, 



1 



