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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-108
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-108
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 27 Mar 2019

Research article | 27 Mar 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Effects of eutrophication on sedimentary organic carbon cycling in five temperate lakes

Annika Fiskal1, Longhui Deng1, Anja Michel1, Philip Eickenbusch1, Xingguo Han1, Lorenzo Lagostina1, Rong Zhu1, Michael Sander1, Martin H. Schroth1, Stefano M. Bernasconi3, Nathalie Dubois2,3, and Mark A. Lever1 Annika Fiskal et al.
  • 1Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
  • 2Surface Waters Research – Management, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
  • 3Department of Earth Sciences, ETH Zurich, Sonneggstrasse 5, 8092 Zurich, Switzerland

Abstract. Even though human induced eutrophication has severely impacted temperate lake ecosystems over the last centuries, the effects on total organic carbon (TOC) burial and mineralization are not well understood. We study these effects based on sedimentary records from the last 180 years in five Swiss lakes that differ in trophic state. We compare changes in content of TOC and modeled TOC accumulation rates through time to historical data on algae blooms, water column anoxia, wastewater treatment, artificial lake ventilation, and water column phosphorus (P) concentrations. We furthermore investigate the effects of eutrophication on rates of microbial TOC remineralization and vertical distributions of microbial respiration reactions in sediments. Our results indicate that the history of eutrophication is well reflected in the sedimentary record. Subsurface peaks in sedimentary TOC coincide with past periods of elevated P concentrations in lake water. Sediments of eutrophic lakes show overall higher rates of microbial respiration, and a higher relative contribution of methanogenesis to total respiration. Yet, a clear impact of lake trophic state on the zonation of microbial respiration reactions is absent. Moreover, even though water column P concentrations have been reduced by ~ 80 % (range: ~ 50–90 %) since the period of peak eutrophication in the 1970s, TOC burial and accumulation rates have only decreased significantly (~ 20 and 25 %) in two of the five lakes. Hereby we found no clear relationship between the magnitude of the decrease in P concentrations and the change in TOC burial and accumulation rate. Instead, artificial lake ventilation, which is used to prevent water column anoxia in eutrophic lakes, may help sustain high rates of TOC burial and accumulation in sediments despite strongly reduced water column P concentrations. Our results provide novel insights into how eutrophication and eutrophication management practices affect organic carbon burial and the distribution of microbial respiration reactions in temperate lakes. These insights are important to understanding how anthropogenic activities affect the size of the carbon pool that is stored globally in lacustrine sediments.

Annika Fiskal et al.
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Annika Fiskal et al.
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