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Deep-ocean vents fuel massive phytoplankton blooms

Researchers have found an aquatic highway that releases nutrients from within the Earth and ferries them up to surface waters off the coast of Antarctica. There the nutrients stimulate explosive growth of microscopic ocean algae. The study suggests that hydrothermal vents -- openings in the seafloor that release hot streams of mineral-rich fluid -- may affect life near the ocean's surface and the global carbon cycle more than previously thought. The research provides the first evidence of iron from the Southern Ocean's depths turning normally low productivity surface waters into hotspots for blooming phytoplankton -- the tiny algae that sustain the marine food web, pull heat-trapping carbon dioxide out of the air and produce a huge amount of the oxygen we breathe. Massive plankton blooms in this region could only be possible with an influx of iron. The researchers quickly ruled out the ocean's most common sources, including continental shelves, melting sea ice, and atmospheric dust, which were too far away. That led them to suspect that the iron must be coming from below, possibly from a string of hydrothermal vents that dot a mid-ocean ridge 750 miles from where the massive blooms inexplicably appeared.

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