ABSTRACT
Sympatric samples of Bathyhiaster vexillifer and Plutonaster bifrons have been collected from a 2200m-deep station in the Rockall Trough, NE Atlantic. The pyloric caecum and gonad AFDW of Bathyhiaster vexillifer show no seasonal variation whereas those of Plutonaster hifrons show a distinct seasonal cycle. The diet of the two species suggests that Bathyhiaster vexillifer is a predator of echinoids, bivalves and gastropods deep in the sediment and, in ingesting these prey items, takes in sediment that has no seasonal organic signal. Conversely, Plutonaster hifrons, although feeding on burrowing echinoids, is essentially a scavenger of organic remains, including fish and feeds at or close to the sediment surface and is consequently subject to the effect of seasonal variation in the organic carbon content of the sediment surface. In this paper we present data of the seasonal variation in the organic carbon content of the stomach contents, pyloric caecum and gonad of both species to determine if these deep sea asteroids are responsible for the organic transformation of the downward flux dominated by sterols to an upward flux dominated by fatty acids.
