Abstract. Bioactive trace metals are critical micronutrients for marine
microorganisms due to their role in mediating biological redox reactions,
and complex biogeochemical processes control their distributions.
Hydrothermal vents may represent an important source of metals to
microorganisms, especially those inhabiting low-iron waters, such as in the
southwest Pacific Ocean. Previous measurements of primordial 3He
indicate a significant hydrothermal source originating in the northeastern (NE)
Lau Basin, with the plume advecting into the southwest Pacific Ocean at
1500–2000 m depth (Lupton et
al., 2004). Studies investigating the long-range transport of trace metals
associated with such dispersing plumes are rare, and the biogeochemical
impacts on local microbial physiology have not yet been described. Here we
quantified dissolved metals and assessed microbial metaproteomes across a
transect spanning the tropical and equatorial Pacific with a focus on the
hydrothermally active NE Lau Basin and report elevated iron and manganese
concentrations across 441 km of the southwest Pacific. The most intense
signal was detected near the Mangatolo Triple Junction (MTJ) and Northeast
Lau Spreading Center (NELSC), in close proximity to the previously reported
3He signature. Protein content in distal-plume-influenced seawater,
which was high in metals, was overall similar to background locations,
though key prokaryotic proteins involved in metal and organic uptake,
protein degradation, and chemoautotrophy were abundant compared to deep
waters outside of the distal plume. Our results demonstrate that trace
metals derived from the NE Lau Basin are transported over appreciable
distances into the southwest Pacific Ocean and that bioactive chemical
resources released from submarine vent systems are utilized by surrounding
deep-sea microbes, influencing both their physiology and their contributions
to ocean biogeochemical cycling.