SS3.04 Biogeochemistry of DOC/DON in a Watershed Context
Date: Wednesday, June 12, 2002
Location: Poster Session - VCC
 
BadeDL, Center for Limnolgy, University of Wisconsin-Madison, Madison, USA, dlbade@students.wisc.edu
Kritzberg, E, , Department of Ecology, Lund University, Lund, Sweden, 
Carpenter, S, R, Center for Limnology, University of Wisconsin-Madison, Madison, USA, 
Cole, J, J, Institute of Ecosystem Studies, Millbrook, USA, 
Pace, M, L, Institute of Ecosystem Studies, Millbrook, USA, 
 
TERRIGENOUS AND AQUATIC ORIGINS OF DISSOLVED ORGANIC CARBON IN LAKES: RESULTS FROM COMPARATIVE AND WHOLE LAKE EXPERIMENTAL APPROACHES
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Dissolved organic carbon (DOC) influences ecosystem processes in lakes, but little is known about the relative contribution of allochthonous and autochthonous forms of DOC. Using stable isotope techniques, the importance of within lake production of DOC is determined. We conducted a study of 32 lakes in Wisconsin and Michigan, and 5 lakes in Sweden to determine the variability of DOC stable isotopes. Values ranged from -29.3 to -22.9 per mil. Many of the lakes had isotope ratios similar to that of terrestrial carbon. However, for some clearwater lakes the DOC isotope values fall near a 1:1 line with isotope values of particulate organic carbon, suggesting that autochthonous production may be a significant source of DOC in some lakes. A whole lake carbon isotope addition was conducted in two lakes. Despite background DOC isotope values being similar to terrestrial carbon, the DOC isotope signature increased between 3 and 6 per mil, owing to inputs from primary producers. We estimated the inputs of algal carbon to be 5 to 20 % relative to terrestrial carbon inputs.