RESULTS 



Megaf auna 



The fauna observable on the sediment surface (megaf auna 

 sensu Grassle et al. 1975) at 800 m depth on the northwest 

 Bermuda slope was rich and varied. Fishermen regard the area as 

 highly productive and the steeply sloping carbonate buttresses 

 may funnel organic material to the comparatively rare flat areas 

 where sediments accumulate. Throughout the area sediments were 

 marked with many holothurian and sea urchin trails and several 

 kinds of burrows including some containing callianassid shrimp. 

 Brittle stars, echinoids ( Hygrosoma ? ) , holothurians, anemones 

 (cerianthids and Actinoscyphia ) and shrimp were abundant. Fish 

 included viper fish ( Chauliodus ? ) , Benthosarus , macrourids, eels, 

 and sharks. 



Brisingid starfish and whip corals were among the most 

 obvious animals on the hard surfaces. 



Macrof auna 



A maldanid polychaete Mastobranchus sp. A was the most 

 common animal in the macrof aunal benthos (Table la). This family 

 of polychaetes does not feed at the sediment surface and is 

 abundant in the deep sea at sites rich in organic material such 

 as the upper slope off New England (Maciolek and Grassle in 

 prep.). The other species are in genera common in most deep-sea 

 environments, however it is unusual for the predatory bivalve 

 Cuspidaria to be among the ten most abundant species. Five of 

 the ten species are probably predators on meiofauna and perhaps 

 small macrof auna. An increased abundance of predators may be 

 another feature of relatively organic-rich deep-sea environments 

 (Turner 1977). 



Response of macrofaunal populations to Sargassum addition 



Each of the species listed in Table lb was found in both 

 cores. Two of the taxa Capitella spp. and Hesionidae spp. were 

 entirely juveniles and could not be separated using external 

 morphology. Densities of the seven most abundant species in the 

 Sargassum cores are greater than any of the species in the 

 background community. The increases in all but one of the 

 abundant species in the Sargassum cores were much greater than 

 the background densities. The two gastropods, the isopod and the 

 polychaete Ophryotrocha were not present among the three cores 

 without Sargassum . The core with lower numbers of Capitella and 

 Ophryotrocha contained a 5.4 cm-long gastropod, Conus nr. 

 fosteria . This species may be feeding on these polychaetes. Of 

 the ten abundant species in the background cores only 



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