HR: 09:00h
AN: B11B-05    [PDF]
TI: Geochemical Short Circuits: How Recycled Ancient Organic Matter Impacts the Biogeochemical Carbon Cycle
AU: * Petsch, S T
EM: spetsch@geo.umass.edu
AF: Dept. Geosciences, University of Massachusetts-Amherst, 611 N. Pleasant St., Amherst, MA 01003 United States
AU: Raymond, P A
EM: peter.raymond@yale.edu
AF: School of Forestry and Env. Studies, Yale University, 205 Prospect St., New Haven, CT 06511 United States
AU: Longworth, B E
EM: brettl@geo.umass.edu
AF: Dept. Geosciences, University of Massachusetts-Amherst, 611 N. Pleasant St., Amherst, MA 01003 United States
AB: Biogeochemists have commonly simplified the geological carbon cycle into fluxes between three carbon reservoirs, namely transfers between dissolved inorganic carbon and organic matter, and dissolved inorganic carbon and carbonate minerals. Using these simplifications a remarkably degree of understanding has developed regarding the pace and character of carbon cycling through geologic time. Isotope ratios in ancient carbonate minerals and organic materials can be understood as the result of specific changes in carbon fluxes and reservoir masses in the geologic past. Because formation and oxidation of organic matter directly involve the gases CO$_{2}$ and O$_{2}$, reconstructions of the geologic history of the carbon cycle lead towards information about the evolution of Earth's atmosphere, greenhouse conditions, and climate change. There is need to constrain the transformations of ancient sedimentary organic matter during rock weathering and riverine transport. A growing body of evidence suggests that these processes are less straightforward and more susceptible to biological activity than can be accommodated in simple models of the geologic carbon cycle. It has been shown that organic matter in sedimentary rocks provides a substrate for the growth of heterotrophic organisms during rock weathering and in the subsurface. Other studies have revealed that rivers draining ancient sedimentary rocks transport highly aged organic carbon to the oceans. Still other research has revealed that this aged organic matter is partially degraded by river and estuarine heterotrophs. Taken together, these efforts reveal that understanding of this key component of the geologic expression of carbon biogeochemistry, namely the transport and transformations of organic carbon between storage in sedimentary rock reservoirs and delivery to the ocean/atmosphere system as inorganic carbon, is less than complete. Building on several small case studies from rivers draining the eastern U.S. and entering the Mid Atlantic Bight, this study explores the possible impacts of ancient organic matter delivery to the oceans on diverse features and processes such as marine carbon pools and turnover rates; net carbon sequestration on land and delivery of terrigenous carbon to the oceans; global organic matter oxidation rates and influence on atmospheric composition; and isotope ratios of marine dissolved inorganic carbon through geologic time.
DE: 0400 Biogeosciences
DE: 1055 Organic geochemistry
DE: 1615 Biogeochemical processes (4805)
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1655 Water cycles (1836)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting