C mass balance of Lake Lunz

Although inland waters are considered important contributors to the carbon (C) cycle, detailed C balances of the stream-lake continuum are sparse
Image: The C mass balance of Lake Lunz during the study period (15 February 2016–15 February 2017). Numbers denote C‐fluxes in t C year−1; arrows and boxes indicate the approximate magnitude (not to scale). Dashed arrows indicate fluxes that likely occur, but were not explicitly quantified in this study (Credit: K. Scholz)

The aim of a team of ecologists of the University of Innsbruck and WasserCluster lunz was to analyze the annual C mass balance of Lake Lunz – a small oligotrophic mountain lake in Lower Austria.

To that end, they combined eddy covariance measurements of lake‐atmosphere net ecosystem CO2 exchange with measurements of fluvial C fluxes (dissolved organic C, DOC; particulate organic C, POC; dissolved inorganic C, DIC) and in‐lake sedimentation.

Overall, about 1500 t C were transferred through the lake, with fluvial C inputs and outputs dominating the lake’s C balance and hydrology acting as the most important control for the fluxes. C inputs and outputs were largely in balance showing that the lake is no clear source of or sink for atmospheric CO2.

The results emphasize the importance of terrestrial C input, the magnitude and timing of which likely is affected by climate change (i.e., increasing temperatures and changing catchment hydrology).


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