"Ocean Circulation as an Architect of Microbial Ecosystems: Tracing the Imprint of the Global Conveyor Belt on South Pacific Microbial Communities"
Talk summary: “Global overturning circulation is a planetary conveyor belt: dense waters sink around Antarctica, spread through the deep ocean for centuries, and eventually rise in the Southern, Indian, and Pacific Oceans, where upwelling and mixing return them to the surface, redistributing heat, nutrients, and carbon. But how does this slow, pervasive movement of water impact marine microbes? To find out, we collected over 300 water samples spanning the full depth of the ocean along the GO-SHIP P18 line in the South Pacific. We found that microbial genomes cluster into six spatial cohorts that are not only delineated by depth, but also circulatory features, like Antarctic Bottom Water formation and ventilation age. Distinct functional signatures also emerged across these circulation-driven zones. For example, genes for light harvesting and iron uptake dominate in surface waters, while adaptations for cold, high pressure, or anaerobic metabolism characterize deep and ancient waters. Antarctic Bottom Water communities also carry hallmarks of rapid genetic exchange, suggesting horizontal gene transfer may help microbes adapt as they sink into the deep ocean. When examining patterns of microbial diversity, we noticed a pervasive “prokaryotic phylocline” in which richness spikes just below the surface mixed layer and remains high to full ocean depth, only dipping slightly in very old water. These results demonstrate that physical circulation, in addition to local seawater properties, governs the distribution of microbial populations and regional functional potential in the Southern Ocean.”
Coffee and snacks provided!