9612291 Cai Collaborative: Carbon and Electron Acceptor Cycling in Lake and Estuarine Sediments The decomposition of organic matter in sediments is an important process which returns nutrients to the overlying water and controls the amount of carbon buried in the worlds oceans and lakes. Bacteria living in sediments degrade organic matter using a variety of oxidants in addition to molecular oxygen. These alternative oxidants include sulfate, nitrate, and the oxides of iron and manganese. It is now clear that these alternative oxidants are intensively recycled near the sediment-water interface and that the amount of decomposition being directly carried out using oxygen is smaller than previously believed. This has important implications for our ability to model the carbon budgets of aquatic ecosystems and other sediment processes, such as the release of contaminants. The PI's will 1) examine the factors controlling the use of alternative oxidants, 2) determine how the age and type of organic matter influences oxidant recycling, and 3) determine whether the presence of alternative oxidants increases total organic matter decomposition.
