The carbon isotope biogeochemistry of microbial mats

Studies of the distribution of stable carbon isotopes within ecosystems frequently offer useful insights into the structure and function of those ecosystems. The isotopic composition of the organic matter in a community such as a microbial mat is controlled by those enzymes which create and subsequently alter organic compounds. The extent to which these enzymes can affect the isotopic composition of organics is influenced by the relative fluxes of carbon, both within a community and between the community and its environment. Because the isotopic composition of organic matter in sedimentary rocks resists thermal alteration better than organic molecular structures, isotopic studies of ancient rocks have been important for Precambrian paleobiology (Hayes et al. 1992; Des Marais et al. 1992a).