Deep-sea epibenthic echinoderms and a temporally varying food supply: results from a one year time series in the N.E. Pacific

Abundance and distribution of epibenthic echinoderms and detrital material at an abyssal site (4100 m) in the N.E. Pacific were examined between June 1994 and June 1995. Camera-sled surveys, time-lapse photographs, and observations from the submersible Alvin revealed a sequence of detrital deposition events. Detrital aggregates were present in summer and fall of 1994 but rare in winter and spring 1995. A layer of white flocculent material covered the sea floor from July through November 1994, constituting the first direct observations of a detrital carpet in this area. Large radiolarian patches also were observed from August 1994 through February 1995. Distribution and abundance of echinoderm species were estimated from camera-sled surveys and showed few consistent temporal patterns. Abundance varied spatially, and distributions generally could not be distinguished from random, in contrast to the clumped pattern observed for detrital aggregates. Statistically, the spatial distributions of several echinoderm species correlated significantly with the distributions of detrital aggregates, but these correlations were not consistent across transects or taxa. The lack of consistent correlation between echinoderm distribution and abundance and the presence of aggregate material is not surprising when the long duration of extensive detrital coverage of the sea floor is considered.