HR: 0800h
AN: H51B-0465    [Abstracts]
TI: Net Organic Carbon Export From Two Temperate Mesotrophic Lakes With Contrasting Hydrologic Characteristics
AU: * Stets, E G
EM: estets@usgs.gov
AF: USGS, 3215 Marine St Suite E-127, Boulder, CO 80303, United States
AU: Striegl, R G
EM: rstriegl@usgs.gov
AF: USGS, PO Box 25046 MS 418 Denver Federal Center, Lakewood, CO 80225, United States
AU: Rosenberry, D O
EM: rosenber@usgs.gov
AF: USGS, PO Box 25046 MS 418 Denver Federal Center, Lakewood, CO 80225, United States
AU: Aiken, G R
EM: graiken@usgs.gov
AF: USGS, 3215 Marine St Suite E-127, Boulder, CO 80303, United States
AU: Winter, T C
EM: tcwinter@usgs.gov
AF: USGS, PO Box 25046 MS 418 Denver Federal Center, Lakewood, CO 80225, United States
AB: Lakes are important to the transport, transformation, and retention of organic and inorganic carbon. Recent evidence strongly suggests that all but the most eutrophic lakes are net consumers of organic carbon (OC) due to inputs from the surrounding watershed and subsequent degradation within these lakes. We constructed a whole-lake carbon budget to test the relative importance of allochthonous carbon sources in two mesotrophic lakes with contrasting hydrologic characteristics; an open-basin lake which receives most of its water as stream input, and a closed-basin lake which receives water only as groundwater and precipitation. We also sought to determine the influence of allochthonous carbon on whole-lake carbon budgets. As expected, the load of allochthonous carbon was much greater in the open-basin lake (910 g C m^-2 yr^-1) than the closed- basin lake (85 g C m^-2 yr^-1) and was dominated by inorganic carbon (IC). Contrary to the findings of recent studies, both lakes were net exporters of OC despite the high allochthonous carbon loads and net flux of CO₂ to the atmosphere. Gross primary production was sufficient to account for the carbon dioxide flux and the conversion of IC to OC resulting in the net export of OC. We believe that the carbon budget of these lakes is largely explained by their geological setting which strongly favors IC inputs. IC inputs can contribute to atmospheric CO₂ flux and encourage macrophyte growth. The importance of the processes identified in this study to other lakes will depend on geologic setting.
DE: 0428 Carbon cycling (4806)
DE: 1845 Limnology (0458, 4239, 4942)
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting