Frontiers in Microbiology
Centre for Marine Ecosystems Research / School of Science
“la Caixa” Foundation (ID 100010434) for VP / European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no 847648 (fellowship code LCF/BQ/PI21/11830020) / Edith Cowan University (G1003456) and chool of Science at Edith Cowan University (G1003362) for VP / Gnts RTI2018-101025-B-I00 / Ramon y Cajal contract (RYC2019-026758-I) / JG by grants CTM2015-70340-R and PID2021-125469NB-C31 of the Spanish Ministry of Science and Innovation and by the Generalitat de Catalunya Consolidated Research Group 2017SGR/1568
Antarctic polynyas are highly productive open water areas surrounded by ice where extensive phytoplankton blooms occur, but little is known about how these surface blooms influence carbon fluxes and prokaryotic communities from deeper waters. By sequencing the 16S rRNA gene, we explored the vertical connectivity of the prokaryotic assemblages associated with particles of three different sizes in two polynyas with different surface productivity, and we linked it to the magnitude of the particle export fluxes measured using thorium-234 (234Th) as particle tracer. Between the sunlit and the mesopelagic layers (700 m depth), we observed compositional changes in the prokaryotic communities associated with the three size-fractions, which were mostly dominated by Flavobacteriia, Alphaproteobacteria, and Gammaproteobacteria. Interestingly, the vertical differences between bacterial communities attached to the largest particles decreased with increasing 234Th export fluxes, indicating a more intense downward transport of surface prokaryotes in the most productive polynya. This was accompanied by a higher proportion of surface prokaryotic taxa detected in deep particle-attached microbial communities in the station with the highest 234Th export flux. Our results support recent studies evidencing links between surface productivity and deep prokaryotic communities and provide the first evidence of sinking particles acting as vectors of microbial diversity to depth in Antarctic polynyas, highlighting the direct influence of particle export in shaping the prokaryotic communities of mesopelagic waters.
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