Particle-Associated Prokaryotic Community Structures in the Bering and Chukchi Seas

In the June 2017 ASGARD cruise in the Bering and Chukchi Seas, 16S rRNA sequencing resolved four size-fractioned bacterial clusters, including one free-living (FL1) and three particle-associated (PA1–PA3) groups.

• Why it matters: Free-living versus particle-associated bacteria drive organic matter cycling, but how this partitioning works in the highly productive, rapidly warming Pacific Arctic shelf is unclear.
• What they did: Across 78 samples from surface, middle, and bottom depths at 12 stations, sequential filtration onto 20, 3, and 0.2 µm filters was analyzed by 16S rRNA gene amplicon sequencing with hierarchical clustering of ASV relative abundances.
• The result: Community structure was not depth-dependent, and distance-based redundancy analysis found salinity as the only significant environmental factor separating communities, implying water-mass origin and lifestyle shape size-fractionated assemblages.

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