109_ 



4.2.2 Benthic Community Recolonization 



4.2.2.1 Evaluation of Recovery 



One of the principle objectives in the tiered monitoring approach to dredged material 

 disposal used in the DAMOS program is to determine the benthic recolonization status at 

 intervals following the completion of disposal mounds or capping projects (Germano et al. 

 1994). For the Seawolf Mound, an infaunal assessment was conducted with grab samples in 

 1997 to evaluate the benthic community and to compare with sediment profile results. Grab 

 samples were collected at six stations to examine the benthic infaunal species diversity and 

 relative abundance over the surface of the Seawolf Mound. Sediment profile images were 

 collected at these stations and over a wider grid in 1997 and 1998 to evaluate the response of 

 benthic succession to the presence of fresh dredged material and confirm the location of cap 

 material. 



The grab sampling stations were selected to represent distinct areas of the mound. A 

 comparison of the bathymetric contours of the mound and sample locations (Figure 2-5) 

 indicated that the stations could be grouped as follows: mound apex (CTR, 75E); mound 

 plateau (150N, 150W, 300WSW); mound apron (300SE). While the initial intention was to 

 sample mound slope deposits (adjacent to the apex), these were very spatially limited at the 

 Seawolf Mound. Most of the mound formed a broad, flat plateau that gently thinned into 

 apron deposits. Within the plateau, the stations can be ordered (from apex to plateau edge 

 150N, 150W, 300WSW). The apron areas are likely to have experienced the least physical 

 disturbance from dredged material disposal whereas the apex should reflect the most 

 frequent disturbance due to elevation and exposure to bottom currents (or may be an area 

 most recently disturbed by disposal). 



Predicted results, based on ecological theory, include the following: moderate 

 diversity at apron stations (reflecting minimal disturbance) with lowered diversity at the 

 mound apex (reflecting greater disturbance), and higher OSI and successional stages at 

 apron stations compared to the apex. Stations located on the mound plateau area should be 

 intermediate between the values with no distinct gradient. The one potential exception 

 would be a transitional increase in diversity within the plateau due to stimulation'of the 

 benthic community from input of organic-rich dredged sediments. This increase in diversity 

 may be difficult to separate from other temporal and spatial variations. 



4.2.2.2 Comparison of Species Composition, Abundance, Successional Stage 



Six stations were sampled by a single 0.04 in grab sample for the purpose of 

 evaluating benthic community composition, abundance, diversity, and the faunal 

 successional status as inferred from REMOTS® image data from the same stations (Stations 



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



