submersible Alvin has been the most efficient vehicle for 

 conducting experiments on the seafloor. The difficulty of 

 scheduling Alvin dives separated by several-month intervals and 

 the availability of relatively inexpensive submersibles for use 

 on the continental slope led us to join the NOAA-sponsored Beebe 

 expedition to the Bermuda slope and use the IUC submersible, 

 Pisces VI. 



METHODS 



We planned an ambitious series of experiments for Pisces 

 dives to the Bermuda slope. The support ship, TWIN DRILL, was 

 anchored at 32°23'N and 64°57'W and the station was just beyond 

 the anchor at 763 m depth. In our first few dives, tracer 

 particles of several kinds were spread on the bottom for studies 

 of feeding behavior and bioturbation of the sediments 

 (Whitlatch). Animals were labelled with tetracycline and placed 

 on the seafloor to study growth rates (Weinberg). Effects of 

 fish and shark scavengers on the benthic communities around 

 baits were also to be studied (Grassle and Snelgrove). Because 

 of problems with weather we were only partially able to complete 

 a study of the effects of Sargassum on the benthic community. 



Floating Sargassum was collected from Bermudian waters by 

 Robert Burns of the Bermuda Biological Station. The algae was 

 kept frozen until deployment on the sea bottom using the Pisces 

 VI. Only encrusting animals remained on the algae and these were 

 killed during freezing. The Sargassum was carried to the bottom 

 in plastic bags and placed in the sediment depressions left after 

 taking 15 by 15 cm box cores. The box core samples were used to 

 characterize the community at the experimental site and were used 

 as controls for the Sargassum treatment. After a period of 37 

 days the Sargassum and surrounding sediment was cored using the 

 same box corer. The Sargassum was mixed in with the sediment and 

 none of the animals were observed clinging to the Sargassum . The 

 terrain at the experimental site was flat, however the general 

 topography at this depth (763 m) was very rugged with many sink 

 holes and crevasses in the terrain between steep carbonate 

 buttresses. 



We had planned to sample six treatment areas and take 

 samples from the surrounding community when the Sargassum was 

 placed and when it was retrieved. Although this was not 

 achieved because of difficulties with weather and logistics, we 

 were able to obtain some results. 



284 



