Production and diversity of microorganisms associated with sinking particles in the subtropical North Pacific Ocean

Sinking particulate organic matter controls the flux of carbon (C) from surface ocean to deep sea. Microorganisms actively colonize particles, but extent which microbial metabolism influences particle export remains uncertain. We conducted experiments quantify rates bacterial production (derived based on 3H-leucine incorporation) and dark C-fixation (based 14C-bicarbonate assimilation) associated with sinking particles collected base euphotic zone (175 m) in subtropical North Pacific Ocean. Seawater was amended filter size-fractionated (0.2, 2, 20 ?m) were measured. Sequencing 16S ribosomal RNA (rRNA) gene amplicons revealed that microorganisms particle-amended treatments differed those unamended seawater controls, enriched putative copiotrophic bacteria. The addition increased (by 6- 9-fold), a lesser 1.7- 4.6-fold), relative most pore sizes < ?m. Normalizing concentrations C yielded statistically indistinguishable between controls. then examined possible relationships attenuation its supply mesopelagic waters, revealing positively related increases supply. Together results our experiments, we suggest processes contribute disaggregation both increase favor mineralization particle-derived matter.