Sources and fates of dissolved organic carbon in lakes as determined by whole-lake carbon isotope additions期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

Sources and fates of dissolved organic carbon in lakes as determined by whole-lake carbon isotope additions

Authors:	Darren L. Bade Stephen R. Carpenter Jonathan J. Cole Michael L. Pace Emma Kritzberg Matthew C. Van de Bogert Rose M. Cory Diane M. McKnight

Affiliation:	(1) Center for Limnology, University of Wisconsin–Madison, 680 N. Park St., Madison, WI 53706, USA;(2) Institute of Ecosystem Studies, Box AB, Millbrook, New York 12545, USA;(3) Department of Ecology/Limnology, Lund University, Lund, S-223 62, Sweden;(4) Institute of Arctic & Alpine Research; Civil & Environmental Engineering, University of Colorado, Boulder, CO 80303, USA;(5) Present address: Institute of Ecosystem Studies, Box AB, Millbrook, New York 12545, USA

Abstract:	Four whole-lake inorganic ¹³C addition experiments were conducted in lakes of differing trophic status. Inorganic ¹³C addition enriched algal carbon in ¹³C and changed the $delta^{13}$ C-DOC by +1.5‰ to +9.5‰, depending on the specific lake. This change in $delta^{13}$ C-DOC represented a significant input of algal DOC that was not completely consumed by bacteria. We modeled the dynamics in $delta^{13}$ C-DOC to estimate the fluxes of algal and terrestrial carbon to and from the DOC pool, and determine the composition of the standing stock. Two experiments in lightly stained, oligotrophic lakes indicated that algal production was the source of about 20% of the DOC pool. In the following year, the experiment was repeated in one of these lakes under conditions of nutrient enrichment, and in a third, more humic lake. Algal contributions to the DOC pool were 40% in the nutrient enriched lake and 5% in the more humic lake. Spectroscopic and elemental analyses corroborated the presence of increased algal DOC in the nutrient enriched lake. Natural abundance measurements of the $delta^{13}$ C of DOC in 32 lakes also revealed the dual contributions of both terrestrial and algal carbon to DOC. From these results, we suggest an approach for inferring the contribution of algal and terrestrial DOC using easily measurable parameters.

Keywords:	Allochthonous Autochthonous Carbon stable isotopes Dissolved organic carbon
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