Abundance and composition of particles and their attached microbiomes along an Atlantic Meridional Transect

Particulate organic matter plays a significant role in the marine carbon cycle. Its sinking exports organic carbon from the surface to deep oceans. Using fractionated filtration, we analysed particles of 3 – 10 µm and >10 µm and their microbiomes in thirty-five stations along a latitudinal transect of the Atlantic Ocean and provide new insights into the composition, community dynamics, and catabolic potential of particle-attached bacteria. Samples were taken during an Atlantic Meridional Transect (AMT22), which traversed six distinctive ocean provinces. Using 16S rRNA amplicon sequencing and fluorescence in situ hybridisation, we could show a strong variation between particle-attached and free-living bacterial communities at each station and across the biogeographical provinces – a dynamic likely driven by chlorophyll a concentrations, temperature, and the oxygen content of the respective biogeographical provinces. Whereas the