Degradation of Colloidal Organic Material and the Formation of Semi-Refractory DOM

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9416740 KIRCHMAN Large numbers of colloids (submicron particles) have been observed in the ocean and are thought to play key roles in several geochemical reactions. Preliminary experiments have led to the hypothesis that colloids are crucial in the production of semi- refractory dissolved organic matter (DOM) with turnover times between truly labile compounds (e.g. free amino acids) and refractory DOM with turnover times 1000 years. Specifically it is hypothesized that compounds associated with colloids are degraded slower than the same compound freely dissolved. Experiments will be conducted to test this hypothesis and to gain more information about turnover of naturally-occurring submicron particles. These experiments will examine: 1) degradation of 3H-protein sorbed to or trapped inside 14C-liposomes which mimic colloids produced by flagellates (flagellate fecal pellets); 2) degradation of 3H- protein sorbed to or trapped inside 14C-liposomes which mimic colloids produced by flagellates (flagellate fecal pellets); and 2) degradation of protein adsorbed to natural colloids. Turnover of colloids will be estimated from the degradation of dual radiolabeled liposomes and from 14C-labeled flagellate fecal pellets. These experiments will be conducted in the Delaware Estuary and coastal waters during the spring bloom and summer, which should give a range of colloid types, concentrations and degradation rates. The work should provide insight into colloid turnover, the degradation of DOM in oceanic environments, and perphaps processes leading to the formation of truly refractory DOM.