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A regime shift from macrophyte to phytoplankton dominance enhances carbon burial in a shallow, eutrophic lake
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2013 (English)In: Ecosphere, ISSN 2150-8925, Vol. 4, no 11, 137Article in journal (Refereed) Published
Abstract [en]

Ecological regime shifts and carbon cycling in aquatic systems have both been subject to increasing attention in recent years, yet the direct connection between these topics has remained poorly understood. A four-fold increase in sedimentation rates was observed within the past 50 years in a shallow eutrophic lake with no surface in- or outflows. This change coincided with an ecological regime shift involving the complete loss of submerged macrophytes, leading to a more turbid, phytoplankton-dominated state. To determine whether the increase in carbon (C) burial resulted from a comprehensive transformation of C cycling pathways in parallel to this regime shift, we compared the annual C balances (mass balance and ecosystem budget) of this turbid lake to a similar nearby lake with submerged macrophytes, a higher transparency, and similar nutrient concentrations. C balances indicated that roughly 80% of the C input was permanently buried in the turbid lake sediments, compared to 40% in the clearer macrophyte-dominated lake. This was due to a higher measured C burial efficiency in the turbid lake, which could be explained by lower benthic C mineralization rates. These lower mineralization rates were associated with a decrease in benthic oxygen availability coinciding with the loss of submerged macrophytes. In contrast to previous assumptions that a regime shift to phytoplankton dominance decreases lake heterotrophy by boosting whole-lake primary production, our results suggest that an equivalent net metabolic shift may also result from lower C mineralization rates in a shallow, turbid lake. The widespread occurrence of such shifts may thus fundamentally alter the role of shallow lakes in the global C cycle, away from channeling terrestrial C to the atmosphere and towards burying an increasing amount of C.

Place, publisher, year, edition, pages
2013. Vol. 4, no 11, 137
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-246044DOI: 10.1890/ES13-00247.1OAI: oai:DiVA.org:uu-246044DiVA: diva2:791736
Available from: 2015-03-02 Created: 2015-03-02 Last updated: 2015-07-02Bibliographically approved

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Scharnweber, Kristin
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