Protist Interactions and Community Structure During Early Autumn in the Kerguelen Region (Southern Ocean)

• Published in: Protist
• Main Authors: Sassenhagen, Ingrid, Irion, Solène, Jardillier, Ludwig, Moreira, David, Christaki, Urania
• Other Authors: Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Nord ), Ecologie Systématique et Evolution (ESE), AgroParisTech-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université du Littoral Côte d'Opale (ULCO), ANR-17-CE01-0013,MOBYDICK,Biodiversité des Ecosystèmes Marins et Dynamique du Carbone dans le secteur de Kerguelen : approche intégrée(2017)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Southern Ocean; single cell sequencing; co-variance analysis; biotic interactions; parasitic Syndiniales; predation; [SDE]Environmental Sciences; Kerguelen; Kerguelen Islands
• Online Access: https://hal.science/hal-04262911; https://doi.org/10.1016/j.protis.2019.125709

International audience This study investigated protist community composition and biotic interactions focusing on microplankton at four distinct sites around the Kerguelen Islands (Southern Ocean) after the summer phytoplankton bloom. Protist diversity in different size fractions, sampled with Niskin bottles and plankton nets, was assessed by sequencing of the V4 18S rDNA region. Combining different approaches, i.e. sequencing of different plankton size fractions, and isolation and sequencing of single cells, provided new insights into microbial interactions in protist communities. The communities displayed high variability, including short-term fluctuations in relative abundance of large protists (>35 μm) highlighted by the plankton net samples. Size fractionation of protist communities showed high concentrations of free Syndiniales spores but relatively few Syndiniales associated with microplankton, suggesting low parasitic infection in early autumn. Co-variance network analyses and sequencing of individually isolated single cells highlighted the important role of Rhizaria as consumers of a wide range of different diatom taxa. The data also raised the hypothesis that different Syndiniales clades might be directly or indirectly associated with some diatom genera, thus suggesting a potentially wider host range of these parasites than has been previously reported. These associations and the potential impact on carbon fluxes are discussed.