Abstract

AbstractIn this article, we challenge the notion that global warming stimulates organic matter mineralization and increases greenhouse gas emissions in lakes via direct temperature effects. We show that the interactive effects of warming and transparency loss due to eutrophication or browning overrides atmospheric warming alone. Thermal shielding enables a longer and more stable stratification that results in bottom‐water cooling, prolonged anoxia, and enhanced carbon preservation in a large proportion of global lakes. These effects are strongest in shallow lakes where an additional burial of 4.5 Tg C yr−1 increases current global estimates by 9%. Despite more burial, the net global warming potential of lakes will increase via enhanced methane production, related to prolonged periods of anoxia, rather than warming. Our understanding of how whole‐lake carbon cycling responds to climate change needs revision, as the synergistic influence of warming and transparency loss has much broader ecosystem level functional consequences.

Highlights

  • In this article, we challenge the notion that global warming stimulates organic matter mineralization and increases greenhouse gas emissions in lakes via direct temperature effects

  • These changes result in the earlier onset and prolonged stratification leading to colder lake bottoms and an extended period of anoxia, which in turn influences carbon cycling (Fig. 4)

  • Our findings provide a mechanistic explanation for the observed increase in carbon burial in lakes, through a reduction in processing associated to bottom cooling and prolonged anoxia

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Summary

CURRENT EVIDENCE

Cold bottoms: Synergistic climate warming and shielding effects increase carbon burial in lakes. Maciej Bartosiewicz ,1,2* Anna Przytulska, Jean-François Lapierre, Isabelle Laurion, Moritz F. Roxane Maranger 2,3 1Department of Environmental Sciences, University of Basel, Basel, Switzerland; 2Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Basel; 3Département des Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada; 4Centre Eau Terre Environnement, Institut National de la Recherche Scientifique, Québec, Québec, Canada

Scientific Significance Statement
Synergistic climate warming and shielding effects
Shielding of bottom waters
Interactive effects of climate and shielding on lake thermal structure
Effects of climate warming and transparency loss on lake carbon processing
Influence of bottom cooling on carbon burial and methanogenesis
Influence of prolonged anoxia on carbon burial and methanogenesis
Implications for lake carbon budgets
Findings
Summary and knowledge gaps
Full Text
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