Characterization of Dissolved Organic Matter in Seawater by Ultrafiltration and Chemical Analysis

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9402361 HEDGES Over the next three years joint research will continue on the sources and reactions of dissolved organic matter (DOM) in seawater. Studies will focus primarily on the 20-30% of total dissolved organic matter which can be gently isolated in relatively large amounts by tangential-flow ultrafiltration. The three central objectives of the research are: 1. To identify the biological sources and transformations of the major DOM components. 2. To elucidate compositional trends among DOM constitutes of different size. 3 To characterize in detail the compositions and associations of the various organic materials comprising seawater DOM. Research to determine the biological and digenetic origins of DOM will emphasize rapid processes occurring in the upper water column where large differences in DOM concentrations and compositions are observed. A better understanding of compositional trends among dissolved organic materials of different size will help to delineate processes affecting DOM cycling and to judge how representative ultrafiltered isolates are of bulk DOM. More detailed characterizations of the compositions and forms of ultra- fitered DOM will aid in distinguishing its biological sources, identifying key transformations, and deconvoluting functional re- lationships among DOM constitutes. This line of research has already provided new insights on both the reactive and refractory components of the immense seawater DOM pool and should continue to yield information useful over wide range of oceanographic studies.