24. 



range. The lower slope and continental rise assemblage is 

 dominated by one trophic type, deposit feeding echinoderms , 

 reflecting the lower nutrient availability in this region. 



The results of the historical survey indicated that the 

 general trend, of gradual replacement of trophic types with 

 increasing depth, is somewhat obscured in submarine canyon 

 habitats. The greater environmental heterogeneity, with regard 

 to substrate variability, afforded by canyons coupled with 

 nutrient enrichment was identified as a probable cause for 

 this phenomenon. Both these factors would allow canyons to 

 support a greater variety of trophic types than found at 

 comparable depths on the slope. The more intensive study of 

 individual canyons undertaken during the field program 

 supports these earlier findings. 



The major taxonomic groups seen during the field survey 

 were fish, crustaceans, anemones, polychaetes, sponges, echin- 

 oderms and corals. Of the three canyons studied Baltimore 

 Canyon most closely resembles a slope habitat. This is 

 reflected by a mapping of the major faunal components found in 

 this canyon (Fig. 9) . The similarity to slope conditions is 

 probably due to the fact that Baltimore Canyon exhibits less 

 substrate variability than either of the two northern canyons. 

 Except for relatively few rock outcrops and occasional occur- 

 rences of cobbles and boulders the walls of this canyon are 



