Microbial Metabolism and Incorporation by the Polychaete Capitella capitata of Aerobically and Anaerobically Decomposed Detritus

Abstract

Detritus derived from Spartind rlllerniflord (cordgrass), Grdcilaric, foliilera (red seaweed), and periphyton (mixed algae) was decomposed aerobically and anaerobically for various lengths of time and then fed to the polychaete Cdpilelld capilald in flow-through microcosms. Rates of detrital mineralization [CO, production), microbial respiration (0, consumption) and biomass (adenosine triphosphate and total adenylates, A,), and net incorporation by C. cdpitata varied with detrital source and length of pre-aging. Oxygen consumpt~on per unit microbial biomass (ymoles 1cgA;' d-') increased linearly with age of the detritus: periphytic algal detritus had the highest daily increase of 4 %, followed by G. foliiferd and S. dlterniflora detritus at 1 % and 0.3 % respectively. Metabolic respiratory quotient (C 4 / O 2) , which varied from < 1 to about 5 0. 1, was a function of detrital source and age; ~t indicated that anaerobic bacteria were important decomposers of detritus. Net incorpordtion rates by C. capitata, microbial biomass, and 0, consumption rates did not dlffer among G. foliifera detritus aged under oxic and anoxic conditions. Rates of CO, production, however, were up to 6 times higher for G. foliifera detritus aged anaerobically. The results suggest that a n a e r o b ~ c metabolism, which causes a high CO, production, could represent a sign~ficant loss of carbon from benthic food webs.