Trans-Pacific explorations of pelagic microbial communities unveil factors affecting the biogeochemical cycles in the dark ocean

Microbial community drives the oceanic biogeochemical cycles through primary production and organic degradation, and thus, local microbial communities interact spatiotemporal biogeochemical cycles. Here, we observed SSU rRNA gene-based community compositions in combination with cell counts and comprehensive physical and geochemical measurements throughout the water columns (0–9758 m) at 49 stations along the three subarctic, subtropical and antarctic transect sampling campaigns in the Pacific Ocean. The results revealed that vertical microbial diversity transition was affected by quality of organic matter, but neither concentrations of oxygen, nutrients, nor organic carbon flux. Moreover, microbial ecosystem below the bathypelagic zone can mostly be explained by a combination of the 8 ubiquitous microbial communities. In contrast, oceanic region-specific communities dominated in the epi- and meso-pelagic zones. The distribution patterns of the microbial communities suggested that the quality of organic matter were varied above the mesopelagic zone, the variable organic matter converged on certain states below the bathypelagic zone, and the ubiquitous microbial communities likely represent degree of organic matter maturation. Moreover, the comparison of the microbial communities among the three transects revealed the impacts of organic matter transportation by antarctic bottom water formation and that with bottom current. The study unveiled the structure of geochemical cycles in deep ocean and the impacts of deep water circulation on geochemical cycles.

Presentation Preference: Oral

Primary Presenter: Takuro Nunoura, Japan Agency for Marine-Earth Science & Technology (JAMSTEC) (takuron@jamstec.go.jp)

Authors:

Taichi Yokokawa, JAMSTEC  (taichi.yokokawa@jamstec.go.jp)

Yoshihiro Takaki, JAMSTEC  (takakiy@jamstec.go.jp)

Takuro Nunoura, JAMSTEC  (takuron@jamstec.go.jp)