Prokaryotic diversity and activity in contrasting productivity regimes in late summer in the Kerguelen region (Southern Ocean)

Type Article
Date 2021-09
Language English
Author(s) Hernandez-Magana Alejandra Elisa1, 2, Liu Yan1, 3, Debeljak Pavla1, 4, Crispi Olivier1, Marie Barbara1, Koedooder Coco1, Obernosterer Ingrid1
Affiliation(s) 1 : Sorbonne Université, CNRS, Laboratoire d'Océanographie Microbienne, LOMIC, F-66650 Banyuls/mer, France
2 : Nordcee, Department of Biology, University of Southern Denmark, Odense M, Denmark
3 : School of Life Sciences, Ludong University, Yantai, China
4 : University of Vienna, Department of Functional and Evolutionary Ecology, A-1090 Vienna, Austria
Source Journal Of Marine Systems (0924-7963) (Elsevier BV), 2021-09 , Vol. 221 , P. 103561 (12p.)
DOI 10.1016/j.jmarsys.2021.103561
WOS© Times Cited 1
Keyword(s) Prokaryotic community composition, 16S rRNA, Amplicon sequence variants, Natural iron fertilization, Southern Ocean
Abstract

Natural iron (Fe) fertilization sustains phytoplankton blooms above the Kerguelen plateau (Indian sector of the Southern Ocean) within otherwise low productive off-plateau waters. In early spring and summer, these diatom-dominated blooms are associated with distinct heterotrophic prokaryotic communities, but whether a structuring effect extends to the post-bloom period has thus far not been investigated. To address this question, we carried out a detailed study of the prokaryotic community composition in the region of Kerguelen Island during late Austral summer (18 February to 27 March 2018; MOBYDICK project). Concentrations of chlorophyll a were seasonally low above the plateau (0.27–0.58 μg Chl a L−1) and in a similar range to those at the 3 off-plateau sites investigated (0.14–0.34 μg Chl a L−1), but we observed an accumulation of dissolved organic carbon and the build-up of heterotrophic prokaryotic biomass in Kerguelen plateau waters. Illumina sequencing of the 16S rRNA gene revealed that the total (DNA-based) and potentially active (RNA-based) prokaryotic communities were structured according to on- and off-plateau sites in the wind-mixed surface layer, in both the free-living (<0.8 μm size fraction) and particle-attached (>0.8 μm size fraction) size fractions. The Amplicon Sequence Variants (ASV) with significantly higher relative abundances in on-plateau surface waters as compared to off-plateau waters belonged to Halieaceae OM60 group, several Flavobacteriaceae, such as the NS5 marine group, Aurantivirga and Ulvibacter, Rhodobacteraceae Loktanella, Saprospiraceae, and the Cryomorphaceae NS10 marine group. ASVs with higher relative abundances in off-plateau waters belonged to the Flavobacteriaceae Formosa, the Rhodobacteraceae Planktomarina and the SAR11 clade. We discuss the potential abiotic and biotic drivers of community composition in late Austral summer and the ecological roles of abundant prokaryotic taxa in Kerguelen plateau waters.

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Hernandez-Magana Alejandra Elisa, Liu Yan, Debeljak Pavla, Crispi Olivier, Marie Barbara, Koedooder Coco, Obernosterer Ingrid (2021). Prokaryotic diversity and activity in contrasting productivity regimes in late summer in the Kerguelen region (Southern Ocean). Journal Of Marine Systems, 221, 103561 (12p.). Publisher's official version : https://doi.org/10.1016/j.jmarsys.2021.103561 , Open Access version : https://archimer.ifremer.fr/doc/00694/80583/