LONG TERM GOAL. Our long-term goal is to understand the action of dissolved enzymes in organic material (OM) degradation and microbial growth. Microorganisms and their enzymes are essential for decomposition of much natural and pollutant OM. In marine environments, much of this material is unavailable for direct incorporation or degradation by microorganisms, either because it is itself too large to be ingested by the cell, or because it is sorbed to some large organic or inorganic substratum. Microbial enzymes, sufactants, and other dissolved cell products that act outside of the cell, hydrolyze, solubilize or otherwise reduce this OM to material that can be incorporated and/or degraded. This initial step often limits the overall rates of material cycling and microbial processes. Thus we wish to understand the action of dissolved enzymes in OM degradation and microbial growth in order to predict the fate of OM in marine environments. In so doing, we hope to contribute to understanding OM and microbe effects on sediment stability and the transmission of sound, as well as to the design of rational plans for pollutant remediation . OBJECTIVES. Our scientific and technical objective is to design and test a predictive model of microbial foraging with cell-free enzymes. Specific objectives for the model are predictions of relative rates of microbial growth under different environmental and microbiological conditions including: different OM concentrations, compositions and distributions; different sediment porosities; different cell sizes; different enzyme properties, etc. Specific objectives for empirical testing are microbial growth rates, enzyme-substrate binding properties, and the relationship between rates and properties.