P.I. Plante, Craig J. Proposal #: 9504505 PROJECT ABSTRACT Bacteria serve dual roles in sedimentary systems: as mineralizers of organic detritus and as food for protozoans and invertebrates. The biomass, production, and community composition of bacteria contribute to the character of these roles. The primary objective of the research is to assess the importance of deposit-feeder ingestion to both qualitative and quantitative aspects of sedimentary bacterial communities. The principal animal selected for intensive study is the deposit-feeding polychaete, Arencola marina. Other polychaetes (Amphitrite johnstoni and Clymenella torquata), hemichordates (Stereobalanus canadensis and Saccoglossus kowlevskyi), an apodous holothuroid (Caudina arenata), and a bivalve mollusc (Macoma balthica) will be investigated for interspecific comparisons. The mechanisms of lysis, keying on digestive surfactants, will be determined. In vitro work will examine 1) the digestive kinetics which affect interactions between surfactants and enzymes; 2) the rate and extent of bacterial digestion, 3) the influence of temperature and reactant concentrations on bacteriolysis, and 4) the effect of gut exposure time on digestive kinematics. In vivo experiments with temperature and food quality will be employed to test predictions resulting from in vitro investigations..
