Biological and Photochemical Transformations of Dissolved Organic Matter in a Subtropical Estuarine Ecosystem

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BENNER Dissolved organic matter (DOM) is the dominant form of organic matter in most aquatic ecosystems and is one of the largest reactive reservoirs of organic carbon on Earth. DOM is the major source of carbon and energy for decomposer microorganisms. These microorganisms are responsible for most of the respiration and carbon and nitrogen cycling in aquatic ecosystems. These studies focus on the cycling of DOM in a shallow subtropical estuary that is highly productive and dominated by seagrasses. Biological and photochemical pathways are hypothesized to be interacting processes which dominate DOM decomposition. Thus, from an ecosystem perspective, sunlight can serve as an important energy source for the non-biological degradation of organic matter and the regeneration of nutrients. Shallow aquatic ecosystems may be receiving a previously unrecognized energy subsidy from sunlight that enhances degradative and regenerative processes and thereby increases the overall productivity of the system. This is important because the interaction between the amount of sunlight an ecosystem receives and the rates of degradation have not been studied in detail in aquatic ecosystems. Sunlight may stimulate productivity both by enhancing photosynthesis and decomposition.