Metagenome-assembled genomes reveal water-mass-associated distribution ecotypes of marine Archaea in the Western Arctic Ocean

Water-mass stratification in the Western Arctic Ocean is linked to distinct archaeal distribution ecotypes, with 155 metagenome-assembled genomes yielding 17 archaeal MAGs across MG-I, MG-II, and MG-III.

• Why it matters: Marine archaeal ecology in the Arctic is poorly resolved, and reported clade-consistent depth patterns for MG-I, MG-II, and MG-III may be confounded by limited sampling and survey resolution.
• What they did: Shotgun metagenomic sequencing from the 2015 U.S. Arctic GEOTRACES expedition (GN01) produced archaeal MAGs from a co-assembly, and temperature, salinity, silicate, and N* were used to define four water mass layers.
• The result: Sample clustering and MAG abundance mapping across several hundred samples separated communities by water mass, showing surface, mid-depth, and deep ecotypes within every marine group, with ecotypes not consistent with MAG phylogeny.

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