HR: 16:15h
AN: B24A-02    [Abstracts]
TI: A Thirty Year Budget of DOC in a Boreal Lake and Watershed
AU: * Hesslein, R H
EM: hessleinr@dfo-mpo.gc.ca
AF: Department of Fisheries and Oceans Canada, Freshwater Institute 501 University Crescent, Winnipeg, MB R3T 2N6 Canada
AU: Guss, D
AF: Department of Fisheries and Oceans Canada, Freshwater Institute 501 University Crescent, Winnipeg, MB R3T 2N6 Canada
AU: Kasian, S E
AF: Department of Fisheries and Oceans Canada, Freshwater Institute 501 University Crescent, Winnipeg, MB R3T 2N6 Canada
AU: Beaty, K G
AF: Department of Fisheries and Oceans Canada, Freshwater Institute 501 University Crescent, Winnipeg, MB R3T 2N6 Canada
AB: Since 1971 we have monitored the hydrologic inflows and outflows and the DOC concentrations to a headwater lake at the Experimental Lakes Area on the Canadian Shield on a weekly basis. In addition to variation due to short term weather we were fortunate to have had near average precipitation for a decade in the 70's, a dry warm decade in the 80's and a wet decade in the 90's. Along with measurements of carbon sedimentation and gas exchange this record has allowed us to interpret changes in the fluxes of DOC from the watershed and the impact of the changes in DOC on the characteristics of the lake. DOC makes up by far the largest part of the carbon flux to the lake and supplies most of the carbon for long term burial in the sediments. About 1/3 of the DOC is removed from the lake each year by decomposition and sedimentation so the decreased fluxes during the dry decade resulted in considerable decrease in DOC concentrations in the lake. This had the consequence of substantially increased light penetration and increased heating of the deep waters of the lake, important factors for the biological community. Volume weighted mean concentrations of DOC are about 50% higher in the 90's than in the 70's and fluxes to the lake in the 90's were about 50% higher. Fires in part of the drainage basin in 1974 and in most of the drainage basin in 1981 had little effect on the DOC concentrations or fluxes to the lake.
DE: 1845 Limnology
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting