Although it is well known that the supply and transformation of nitrogen from one form to another are major determinants of biological productivity in the marine environment, we still know very little about the processes involved in the transformation of nitrogen from organic to inorganic form. To approach this problem, scientists from the State University of New York at Stony Brook will study the cycling of amino acids, peptides, and proteins in two inshore marine environments, Long Island Sound and Chesapeake Bay. The specific goals are to determine the environmental conditions under which hydrolysis of peptides and proteins occurs, whether hydrolysis is the rate-limiting step in amino acid uptake, and the sources of exoenzymatic activity in seawater. Proteolytic activity, cell-surface oxidation, and amino acid uptake would be measured under various environmental conditions to determine how they are affected by differences in biomass, community structure, and amount of dissolved organic nitrogen and inorganic nitrogen. The Chesapeake Bay field studies would be carried out cooperatively with scientists from the Horn Point Environmental Laboratory which is situated on the Bay.