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) 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.
| Originalsprog | Engelsk |
|---|---|
| Artikelnummer | 103561 |
| Tidsskrift | Journal of Marine Systems |
| Vol/bind | 221 |
| Antal sider | 12 |
| ISSN | 0924-7963 |
| DOI | |
| Status | Udgivet - sep. 2021 |
Bibliografisk note
Funding Information:We thank B. Quéguiner, the PI of the MOBYDICK project, for providing us the opportunity to participate to this cruise, and the captain and crew of the R/V Marion Dufresne for their enthusiasm and support aboard during the MOBYDICK– THEMISTO cruise ( https://doi.org/10.17600/18000403 ). This work was supported by the French oceanographic fleet (“Flotte océanographique française”), the French ANR (“ Agence Nationale de la Recherche ”, AAPG 2017 program, MOBYDICK Project number: ANR-17-CE01-0013 ), and the French Research program of INSU-CNRS LEFE/CYBER (“Les enveloppes fluides et l'environnement” – “Cycles biogéochimiques, environnement et ressources”). We thank P. Catala for flow cytometry analyses. We are grateful to A. Lafond and J. Legras for sharing with us the diatom species abundances obtained by microscopic observations. We thank the GenoToul Bioinformatics platform ( http://bioinfo.genotoul.fr/ ) for providing computing resources. Y.L. was supported by the China Scholarship Council (CSC; No. 201606330072 ). Three reviewers provided constructive comments that helped improve a previous version of the manuscript.
Funding Information:
We thank B. Qu?guiner, the PI of the MOBYDICK project, for providing us the opportunity to participate to this cruise, and the captain and crew of the R/V Marion Dufresne for their enthusiasm and support aboard during the MOBYDICK? THEMISTO cruise (https://doi.org/10.17600/18000403). This work was supported by the French oceanographic fleet (?Flotte oc?anographique fran?aise?), the French ANR (?Agence Nationale de la Recherche?, AAPG 2017 program, MOBYDICK Project number: ANR-17-CE01-0013), and the French Research program of INSU-CNRS LEFE/CYBER (?Les enveloppes fluides et l'environnement? ? ?Cycles biog?ochimiques, environnement et ressources?). We thank P. Catala for flow cytometry analyses. We are grateful to A. Lafond and J. Legras for sharing with us the diatom species abundances obtained by microscopic observations. We thank the GenoToul Bioinformatics platform (http://bioinfo.genotoul.fr/) for providing computing resources. Y.L. was supported by the China Scholarship Council (CSC; No. 201606330072). Three reviewers provided constructive comments that helped improve a previous version of the manuscript. Demultiplexed sequence files are available in NCBI under accession number PRJNA679029.
Publisher Copyright:
© 2021 Elsevier B.V.