Dissolved organic carbon export and internal cycling in small, headwater lakes

Edward G. Stets; Robert G. Striegl; George R. Aiken

doi:10.1029/2010gb003815

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Dissolved organic carbon export and internal cycling in small, headwater lakes

Edward G. Stets·Robert G. Striegl·George R. Aiken

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Abstract

Carbon (C) cycling in freshwater lakes is intense but poorly integrated into our current understanding of overall C transport from the land to the oceans. We quantified dissolved organic carbon export (DOC X ) and compared it with modeled gross DOC mineralization (DOC R ) to determine whether hydrologic or within-lake processes dominated DOC cycling in a small headwaters watershed in Minnesota, USA. We also used DOC optical properties to gather information about DOC sources. We then compared our results to a data set of approximately 1500 lakes in the Eastern USA (Eastern Lake Survey, ELS, data set) to place our results in context of lakes more broadly. In the open-basin lakes in our watershed ( n = 5), DOC X ranged from 60 to 183 g C m −2 lake area yr −1 , whereas DOC R ranged from 15 to 21 g C m −2 lake area yr −1 , emphasizing that lateral DOC fluxes dominated. DOC X calculated in our study watershed clustered near the 75th percentile of open-basin lakes in the ELS data set, suggesting that these results were not unusual. In contrast, DOC X in closed-basin lakes ( n = 2) was approximately 5 g C m −2 lake area yr −1 , whereas DOC R was 37 to 42 g C m −2 lake area yr −1 , suggesting that internal C cycling dominated. In the ELS data set, median DOC X was 32 and 12 g C m −2 yr −1 in open-basin and closed-basin lakes, respectively. Although not as high as what was observed in our study watershed, DOC X is an important component of lake C flux more generally, particularly in open-basin lakes.

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Edward G. Stets, Robert G. Striegl, George R. Aiken. 2010-10-27. Dissolved organic carbon export and internal cycling in small, headwater lakes. https://doi.org/10.1029/2010gb003815

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