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<p>Cultural eutrophication has contributed to enhanced phytoplankton biomass in lakes around the world, leading to an overall increase in sedimentary carbon (C) sequestration since the twentieth century. However, the effects of land-use changes and restoration initiatives on sedimentary C sequestration are not yet well understood. To address this gap, we applied the paleolimnological approach to a temperate, hardwater site, Lake Aiguebelette, to investigate temporal changes in organic and inorganic C sequestration in relation to changes in C supplies, lake primary production, and preservation conditions over the past 300 years. Our results show that C sequestration has constantly increased in Lake Aiguebelette over the last 150 years due to local human disturbances. A&#xa0;first&#xa0;increase in lake-carbon sequestration was&#xa0;recorded&#xa0;between 1850 and&#xa0;the&#xa0;1860s, a period marked by deforestation,&#xa0;marsh drainage, and&#xa0;lake-level regulation — activities that collectively accelerated carbonate supply and precipitation in the lake. Subsequently, lake organic biomass production exceeded inorganic supplies&#xa0;and became&#xa0;the main contributor&#xa0;to&#xa0;total C sequestration. A period of nutrient enrichment in lake waters spanned&#xa0;from&#xa0;the 1950s&#xa0;to the1990s, which&#xa0;coincided with&#xa0;increased lake biomass and reduced hypolimnetic oxygen conditions. Over the last three decades,&#xa0;C sequestration has continued to increase, despite the reduction in nutrient loads following restoration measures. Our results suggest a long history of human disturbances, leading to a succession of perturbations in the carbon cycle in Lake Aiguebelette&#xa0;that favored&#xa0;C supplies and C fixation. In contrast, recent C burial appears to be controlled by decreased bottom-water oxygen conditions, despite&#xa0;improvements&#xa0;in surface-water quality. Overall, our study highlights a range of processes&#xa0;that&#xa0;can influence C burial over time, with recent reductions in nutrient loading during an era of climate warming resulting in both improved water quality and enhanced C storage.</p>

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Increasing carbon burial over recent decades despite re-oligotrophication in deep peri-alpine Lake Aiguebelette, France

  • 期刊论文

  • 发表日期：

    2025年6月4日

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  • Jean-Philippe Jenny,
  • Cécilia Barouillet,
  • Isabelle Domaizon,
  • David Etienne,
  • Irene Gregory-Eaves,
  • Olivia Itier-Desgué,
  • Andrea Lami,
  • Erwan Messager,
  • Pierre Sabatier,
  • Julie Rotschi

摘要

Cultural eutrophication has contributed to enhanced phytoplankton biomass in lakes around the world, leading to an overall increase in sedimentary carbon (C) sequestration since the twentieth century. However, the effects of land-use changes and restoration initiatives on sedimentary C sequestration are not yet well understood. To address this gap, we applied the paleolimnological approach to a temperate, hardwater site, Lake Aiguebelette, to investigate temporal changes in organic and inorganic C sequestration in relation to changes in C supplies, lake primary production, and preservation conditions over the past 300 years. Our results show that C sequestration has constantly increased in Lake Aiguebelette over the last 150 years due to local human disturbances. A first increase in lake-carbon sequestration was recorded between 1850 and the 1860s, a period marked by deforestation, marsh drainage, and lake-level regulation — activities that collectively accelerated carbonate supply and precipitation in the lake. Subsequently, lake organic biomass production exceeded inorganic supplies and became the main contributor to total C sequestration. A period of nutrient enrichment in lake waters spanned from the 1950s to the1990s, which coincided with increased lake biomass and reduced hypolimnetic oxygen conditions. Over the last three decades, C sequestration has continued to increase, despite the reduction in nutrient loads following restoration measures. Our results suggest a long history of human disturbances, leading to a succession of perturbations in the carbon cycle in Lake Aiguebelette that favored C supplies and C fixation. In contrast, recent C burial appears to be controlled by decreased bottom-water oxygen conditions, despite improvements in surface-water quality. Overall, our study highlights a range of processes that can influence C burial over time, with recent reductions in nutrient loading during an era of climate warming resulting in both improved water quality and enhanced C storage.