[OCES Seminar] Linking Microbial Community Structure and Carbon Remineralization Across the Deep Pacific Ocean 
 

The deep Pacific Ocean is the largest long-term carbon reservoir, yet the biological mechanisms sustaining its stability remain unclear. We combined basin-scale estimates of prokaryote respiration with full-depth microbial community analyses to link carbon remineralization processes with community structure. Prokaryote respiration closely matched oxygen utilization and carbon remineralization rates, indicating a quantitatively steady-state system. Community analyses revealed a clear vertical transition: diverse, region-specific assemblages in the upper ocean and ubiquitous communities dominating the bathy- and abyssopelagic zones. These deep communities appear structured by the quality of organic matter, reflecting a shift from labile to more recalcitrant substrates with depth. Our results suggest that the deep Pacific carbon cycle is sustained by both balanced microbial respiration and stabilized community structure adapted to mature organic matter.