Massive Southern Ocean phytoplankton bloom fed by iron of possible hydrothermal origin

Primary production in the Southern Ocean (SO) is limited by iron availability. Hydrothermal vents have been identified as a potentially important source of iron to SO surface waters. Here we identify a recurring phytoplankton bloom in the high-nutrient, low-chlorophyll waters of the Antarctic Circumpolar Current in the Pacific sector of the SO, that we argue is fed by iron of hydrothermal origin. In January 2014 the bloom covered an area of similar to 266,000 km(2) with depth-integrated chlorophyll a > 300 mg m(-2), primary production rates >1 g C m(-2) d(-1), and a mean CO2 flux of -0.38 g C m(-2) d(-1). The elevated iron supporting this bloom is likely of hydrothermal origin based on the recurrent position of the bloom relative to two active hydrothermal vent fields along the Australian Antarctic Ridge and the association of the elevated iron with a distinct water mass characteristic of a nonbuoyant hydrothermal vent plume.

Automated summary

The primary production in the Southern Ocean is limited by iron availability, with hydrothermal vents identified as a potential source of iron. A significant phytoplankton bloom occurred in the Pacific sector of the Antarctic Circumpolar Current in January 2014, likely fueled by iron of hydrothermal origin.