GENERAL OBSERVATIONS 



The canyon has a higher diversity than does the slope, reflecting the 

 addition of sessile filter feeders to the background slope fauna. At mid- 

 slope depths, carnivores predominate on the slope, while filter feeders are 

 preeminent at all depths in the canyon axis. In both regions, diversity is 

 higher on hard substrate than on soft. Diversity also increases with the size 

 of the hard substrate, being lowest in cobble areas, and highest on cliffs. 



OTHER CANYONS 



In 1977 Alvin made three dives in Oceanographer Canyon, three in Heezen 

 Canyon, and one in Corsair Canyon. The same kind of cluster analysis used in 

 Lydonia Canyon shows disparity among the three canyons, possibly reflecting 

 the disparity in their morphology and corresponding differences in their 

 physical regimes: Oceanographer Canyon is wide, with low stepped cliffs and 

 comparatively heavy sediments; Heezen is very narrow and deeply incised, with 

 large Eocene chalk cliff flanking the axis. Corsair is mostly sediment 

 covered with limited exposures of hard substrate. Only some of the faunal 

 differences among the canyons could be attributed to availability of hard 

 substrate. 



CONCLUSIONS 



■ Distributions of megafaunal assemblages in the Georges Bank canyons 

 are complex with a high degree of patchiness in many of their faunal 

 constituents. 



■ The canyons are marked by high concentrations of sessile filter 

 feeders (corals and sponges). 



■ The different patterns reflect substrate heterogeneity, enhanced 

 current speeds within the canyons, resuspension events, and probably 

 the concentration of fine particles in the axis. 



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