A mussel bed dominated by Mytilus edulis contained large concentrations of living consumer biomass, with over 14 kg dry weight/m2 distributed among eleven species. An additional 14.4 kg dry weight/m2 was present as empty shell fragments that contributed to community structure. Field measurements of community respiration for this dense animal system showed a roughly hyperbolic response to increasing current speed. In still water, oxygen uptake was 0.2g O2/m2/hr while in currents over 0.1 m/sec it quickly rose to about 2.7 g O2/m2/hr.