Deposit feeders ingest bulk sediment and digest associated organic components, and they thus can affect rates and extents of organic matter degradation and burial in the sediments. How deposit feeders make a living by exploiting a food resource, the bulk of which is mineral grains, is as yet poorly understood. Within the framework of digestion theory and gut- reactor models can provide a rigorous framework for quantifying digestive processes. However, quantitative application of the theory and models requires description of digestive reaction kinetics, and the enzymology of digestion in deposit feeders is poorly known. I thus propose to develop a research program to describe and quantify enzymatic digestion in deposit feeders, i.e. to identify and quantify the digestive parameters that ate represented in gut-reactor models by the variable, -rA, the expression for digestive reaction rate. The ultimate goal of my research is to determine the ranges of digestive performance exhibited by deposit feeders as food resources vary. The specific goals of this planning proposal are to determine the suites of digestive enzymes present in deposit feeders' guts and to determine the potential for changes in enzyme complements and activities in response to changes in food resources (physiological acclimation). Identification of the types of enzymes present in deposit feeders' guts is a necessary starting point for studies of digestive performance. I also propose to conduct several simple digestive acclimation experiments to determine how the types and amounts of enzymes present in a deposit feeders' gut may vary with food resources. The combination of a descriptive survey with experimental examinations of digestive acclimation of food resources will provide the foundation for future studies of digestive performance.
