Production and Carbon Isotopic Composition of Bacterial CO2 in Deep Coastal Plain Sediments of South Carolina

Abstract

AbstractThe production and carbon isotopic composition of bacterial CO2 in cores of deep Coastal Plain sediments from South Carolina were measured. Rates of bacterial CO2 production in laboratory incubations ranged from 0 to 2,750 nanomoles of CO2 per gram of sediment per day. On average, C02 production was greater in downdip sediments than in updip sediments. There was no relation between CO2 production and total organic carbon content of the sediment. The carbon isotopic composition of bacterial CO2 ranged from ‐29.7 to ‐18.0 per mil and is controlled in part by the isotopic composition of the sedimentary organic matter from which the CO2 is derived. The isotopic composition of CO2 from downdip sediments was enriched in 13C by about 50/00, on average, relative to CO2 from updip sediments.Measurements of the production and carbon isotopic composition of bacterial CO2 given here provide evidence linking bacterial CO2 to dissolved inorganic carbon in Coastal Plain aquifers of South Carolina.