Stable carbon and nitrogen isotope compositions of bulk organic matter, lipids and selected pigments (chlorophylls a, b and c; B-cartene; and phaeopigments) will be measured to investigate the sources and cycling of organic matter in slected marine environments. Preparative-scale high-performance liquid chromatographic methods will be used to isolate sufficient quantities of pure parent pigments for precise and accurate stable isotope analysis. Carbon and nitrogen uptake and biosynthetic utilization cause characteristic kinetic fractionations that can be used to define the "life histories" of of specific organic pools. While determinations of bulk organic matter properties are useful, the stable isotopic analysis of specific marker compounds holds great promise for deconvoluting organic matrices produced by multiple sources and complex processes. Field studies will include the characterization of three well- defined oceanographic settings to evaluate the variability, utility and limitations of pigment-specific stable isotope distributions for (1) resolving terrestrial and marine biomass; (2) differentiating organic matter sources in sediments; and (3) determining the relative importance of "new" vs. "recycled" production in the upper water column. //
