Temporal dynamics of lacustrine microbial eukaryotes inferred from paleogenetic approaches : tracking the impacts of climate change and nutrients enrichment

• Main Author: Capo, Éric
• Other Authors: Centre Alpin de Recherche sur les Réseaux Trophiques et Ecosystèmes Limniques (CARRTEL), Institut National de la Recherche Agronomique (INRA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry ), Université Grenoble Alpes, Isabelle Domaizon, Fabien Arnaud, Didier Debroas
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2016
• Subjects: Climate warming; Eutrophication; Paleolimnology; Sedimentary DNA; High-Throughput sequencing; Microbial eukaryotes; Microbes eucaryotes; Séquençage massif; ADN sédimentaire; Paléolimnologie; Eutrophisation; Réchauffement climatique; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Greenland; Igaliku
• Online Access: https://tel.archives-ouvertes.fr/tel-01517017; https://tel.archives-ouvertes.fr/tel-01517017/document; https://tel.archives-ouvertes.fr/tel-01517017/file/CAPO_Eric_2016_archivage.pdf

Eutrophication and climate warming are key factors governing lake functioning. However, there is a lack of knowledge about the response of microbial eukaryotic communities to these forcing factors even though microbial eukaryotes represent a huge taxonomic and functional diversity within lacustrine trophic networks. Paleolimnology has a well-established reputation for providing valuable insights into the drivers of biological assemblages over long time scales. The emergence of DNA analyses of lake sediments opens up many new opportunities for the reconstruction of past lacustrine biodiversity, including taxa that do not leave distinct morphological fossils. The present work aimed (i) to gain knowledge about the preservation of microbial eukaryotes DNA in lacustrine sediments (ii) to apply DNA-based methods to dated sediments in order to reveal the long-term dynamics (centennial to millennial) of microbial eukaryotes related to climatic and anthropogenic changes. The results obtained for Lake Bourget demonstrated the good efficiency of planktonic DNA archiving in recent sediments for most of microbial groups (chrysophyceae, chytrids, chlorophytes, cercozoa, ciliates, dinophyceae …). In complement, the use of a unique collection of freeze cores of varved sediment (Lake Nylandssjön, Sweden) allowed to assess the effects of diagenetic processes on microbial eukaryotes DNA occurring during the first years of burying. While the richness of the microbial eukaryotic community was not impacted, modifications were detected on the community structure during the first 15 years after deposition, then the DNA signal became stable. The paleoecological approach was applied to quantify centennial to millennial-scale dynamics on two deep peri-alpine lakes selected for their contrasted trophic history (lakes Bourget and Annecy, France) and two lakes with contrasted typologies (Lake Bourget, France and Lake Igaliku, Greenland). The results showed that some community rearrangements were concomitant with climate events (i.e. medieval ...