Increasing Hydrostatic Pressure Impacts the Prokaryotic Diversity during Emiliania huxleyi Aggregates Degradation

• Published in: Water
• Main Authors: Christian Tamburini, Marc Garel, Aude Barani, Dominique Boeuf, Patricia Bonin, Nagib Bhairy, Sophie Guasco, Stéphanie Jacquet, Frédéric A. C. Le Moigne, Christos Panagiotopoulos, Virginie Riou, Sandrine Veloso, Chiara Santinelli, Fabrice Armougom
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2021
• Subjects: biological carbon pump; carbon cycle; mesopelagic; mineral ballast; coccolithophorid; Emiliania huxleyi; Hydraulic engineering; TC1-978; Water supply for domestic and industrial purposes; TD201-500; North Atlantic
• Online Access: https://doi.org/10.3390/w13192616; https://doaj.org/article/d167a2cf0a0e4c328ce631cb7ee80015

In the dark ocean, the balance between the heterotrophic carbon demand and the supply of sinking carbon through the biological carbon pump remains poorly constrained. In situ tracking of the dynamics of microbial degradation processes occurring on the gravitational sinking particles is still challenging. Our particle sinking simulator system (PASS) intends to mimic as closely as possible the in situ variations in pressure and temperature experienced by gravitational sinking particles. Here, we used the PASS to simultaneously track geochemical and microbial changes that occurred during the sinking through the mesopelagic zone of laboratory-grown Emiliania huxleyi aggregates amended by a natural microbial community sampled at 105 m depth in the North Atlantic Ocean. The impact of pressure on the prokaryotic degradation of POC and dissolution of E. huxleyi -derived calcite was not marked compared to atmospheric pressure. In contrast, using global O 2 consumption monitored in real-time inside the high-pressure bottles using planar optodes via a sapphire window, a reduction of respiration rate was recorded in surface-originated community assemblages under increasing pressure conditions. Moreover, using a 16S rRNA metabarcoding survey, we demonstrated a drastic difference in transcriptionally active prokaryotes associated with particles, incubated either at atmospheric pressure or under linearly increasing hydrostatic pressure conditions. The increase in hydrostatic pressure reduced both the phylogenetic diversity and the species richness. The incubation at atmospheric pressure, however, promoted an opportunistic community of “fast” degraders from the surface ( Saccharospirillaceae , Hyphomonadaceae, and Pseudoalteromonadaceae ), known to be associated with surface phytoplankton blooms. In contrast, the incubation under increasing pressure condition incubations revealed an increase in the particle colonizer families Flavobacteriaceae and Rhodobacteraceae , and also Colwelliaceae, which are known to be adapted to high ...