To help identify key microbial taxa driving carbon export during a spring phytoplankton bloom in the subarctic ocean, we examined prokaryotic and eukaryotic microbiome of sinking and suspended particles collected at initial (March) and later (May) bloom stages. The weighted gene correlation network analysis (WGCNA) detected four microbial subnetworks preferentially associated with the sinking particles. Distinct distribution patterns of these subnetworks across water layers (chlorophyll maximum, pycnocline, mesopelagic, and bottom boundary) and months suggest that they occupied different niches. The partial least square (PLS) regression result indicated that one subnetwork (MiB) was a significant predictor of the sinking particulate organic carbon flux in the upper layers (r² = 0.41, p = 0.0041). Among the MiB members, the prokaryotic key taxa responsible for the PLS regression model, assessed using the variable importance in projection score, consisted of polymer degraders such as Bacteroidota (Saprospiraceae, Flavobacteriaceae) and Gammaproteobacteria (Halieaceae). The corresponding eukaryotic taxa consisted of not only a bloom forming taxon (Bacillariophyta) but also pseudofungi (Oomycetes) and fungi (Chytridiomycetes). Our results revealed the key microbial taxa potentially involved in the regulation of biological carbon pump during phytoplankton bloom.

Primary Presenter: Akiko EBIHARA, Atmosphere and Ocean Research Institute, The University of Tokyo (ebihara-a@aori.u-tokyo.ac.jp)

Authors:

Akiko EBIHARA, Atmosphere and Ocean Research Institute, The University of Tokyo  (ebihara-a@aori.u-tokyo.ac.jp)

Hideki FUKUDA, Atmosphere and Ocean Research Institute, The University of Tokyo  ()

Yosuke YAMADA, Japan Agency for Marine-Earth Science and Technology  ()

Taichi YOKOKAWA, Japan Agency for Marine-Earth Science and Technology  ()

Toshi NAGATA, Atmosphere and Ocean Research Institute, The University of Tokyo  ()