Net incorporation rates of detritus derived from carbon-14 labelled seaweed, Gracilaria foliifera (Harvey) Taylor, by the polychaete, Nereis succinea (Frey and Leuckart), were measured in the presence and absence of the ciliate, Aspidisca sp. Net incorporation rates averaged 79 in the absence and 129 μg dry wt detritus·mg-1 dry wt worm·day-1 in the presence of ciliates. Ciliates did not significantly affect oxidation rates. In the presence of Nereis succinea, however, oxidation rates approximately doubled due to respiration and feeding activity. The increase in net incorporation probably resulted from a combination of stimulation of bacteria by grazing, fragmentation of detritus by ciliates, and ingestion of ciliates. The rate of heterotrophic uptake of tritiated glucose was used as a relative measure of microbial activity in the sediment. Glucose flux was greatest when N. succinea and Aspidisca were present together. Our data clarify the regulatory rôle of the microfaunal community in the transfer of energy from detritus to the macrodetritivore and the rôle of macrofauna in enhancing microbial activity in the sediment through bioturbation. © 1979.
