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<p>Alpine lakes in the Mediterranean region are experiencing rapid warming, posing a threat to aquatic ecosystem diversity and functioning. Documenting how high-altitude lake ecosystems have responded to past warming and cooling events is of interest to scale modern changes in a long-term context, and to inform management strategies. This paleoenvironmental study focuses on Lake Petit (2200&#xa0;m a.s.l., Southern Alps) and combines the analysis of subfossil diatoms and inorganic and organic sediment composition over the last 14,000&#xa0;years. The results show a major ecosystem shift at the Late Glacial-Holocene transition, ca. 12,000&#xa0;years ago. In addition, the alternating dominance of diatoms from the Fragilariaceae (e.g., <i>Pseudostaurosira pseudoconstruens, Staurosira venter</i>) and Gomphonemaceae (e.g., <i>Gomphonema elegantissimum</i>), along with high-amplitude fluctuations in biogenic silica concentrations, highlight rapid ecological shifts at four distinct periods: 10,100–9800, 9200–9000, 8100–8000, and 7000–6900&#xa0;cal&#xa0;yr BP. These shifts reveal the occurrence of four centennial-scale cooling events at the beginning of the Holocene. During the warmer Middle-Holocene period, diatom assemblages are dominated by <i>Staurosirella neopinnata</i>, ending with a shift coinciding with the 4.2&#xa0;ka climate event, described in a previous study. A progressive return of <i>S. neopinnata</i> is observed nowadays. Our findings suggest that during the Early Holocene, the lake ecosystem was capable of buffering centennial-scale cooling events, consistently returning to previous conditions. However, the two phases of major long-lasting ecological shift that occurred 7000 and 4200&#xa0;years ago, likely driven by catchment-related factors such as pedogenesis and vegetation dynamics, led to stepwise changes in ecosystem functioning baselines. This paper raises once again questions about the capacity of modern aquatic high-altitude lake ecosytems to recover from ongoing climate change when local baselines are no longer in equilibrium with natural variability.</p>

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Rapid shifts in an alpine lake ecosystem of the Southern Alps in response to Late Glacial-Holocene centennial-scale events inferred from diatom assemblages

  • 期刊论文

  • 发表日期：

    2025年6月5日

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  • Rosine Cartier,
  • Christine Paillès,
  • Elodie Brisset,
  • Kazuyo Tachikawa,
  • Sandrine Conrod,
  • Lenka Brousset,
  • Christian Marschal,
  • Pascal Wong-Wah-Chung,
  • Loris Cagnacci,
  • Edouard Bard,
  • Laurence Vidal

摘要

Alpine lakes in the Mediterranean region are experiencing rapid warming, posing a threat to aquatic ecosystem diversity and functioning. Documenting how high-altitude lake ecosystems have responded to past warming and cooling events is of interest to scale modern changes in a long-term context, and to inform management strategies. This paleoenvironmental study focuses on Lake Petit (2200 m a.s.l., Southern Alps) and combines the analysis of subfossil diatoms and inorganic and organic sediment composition over the last 14,000 years. The results show a major ecosystem shift at the Late Glacial-Holocene transition, ca. 12,000 years ago. In addition, the alternating dominance of diatoms from the Fragilariaceae (e.g., Pseudostaurosira pseudoconstruens, Staurosira venter) and Gomphonemaceae (e.g., Gomphonema elegantissimum), along with high-amplitude fluctuations in biogenic silica concentrations, highlight rapid ecological shifts at four distinct periods: 10,100–9800, 9200–9000, 8100–8000, and 7000–6900 cal yr BP. These shifts reveal the occurrence of four centennial-scale cooling events at the beginning of the Holocene. During the warmer Middle-Holocene period, diatom assemblages are dominated by Staurosirella neopinnata, ending with a shift coinciding with the 4.2 ka climate event, described in a previous study. A progressive return of S. neopinnata is observed nowadays. Our findings suggest that during the Early Holocene, the lake ecosystem was capable of buffering centennial-scale cooling events, consistently returning to previous conditions. However, the two phases of major long-lasting ecological shift that occurred 7000 and 4200 years ago, likely driven by catchment-related factors such as pedogenesis and vegetation dynamics, led to stepwise changes in ecosystem functioning baselines. This paper raises once again questions about the capacity of modern aquatic high-altitude lake ecosytems to recover from ongoing climate change when local baselines are no longer in equilibrium with natural variability.