Hydrothermal Vents Fertilize Oceans With Fool’s Gold

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Deep in the oceans, hydrothermal vents spew superheated water full of dissolved minerals. The vents spawn diverse communities of unique creatures that not only withstand the extreme temperatures and acidity but even depend on the chemicals in the water to live. New research in Nature Geoscience shows that these vents may be having even greater impacts by providing fertilizer for ocean life far away.

Researchers from the University of Delaware and elsewhere traveled to the Lau Basin in the Pacific Ocean and sampled waters from the hydrothermal vents using a remotely operated vehicle. They found nanoparticles of pyrite---a mineral composed of iron and sulfur more commonly known as fool's gold---1,000 times smaller than the width of a hair. Scientists had known that the waters contained pyrite but thought that the particles were big enough that they quickly settled onto the ocean floor. But these tiny particles don't do that. They're small enough that they disperse into the ocean, where they stay suspended. And this type of iron doesn't oxidize (that is, rust) very quickly, so it can remain in the water even longer, available for the plankton and bacteria that need it.

"As pyrite travels from the vents to the ocean interior and toward the surface ocean, it oxidizes gradually to release iron, which becomes available in areas where iron is depleted so that organisms can assimilate it, then grow," says study co-author, George Luther of the University of Delaware. "It's an ongoing iron supplement for the ocean---much as multivitamins are for humans."

The vents aren't the only source of iron in the ocean, but some researchers have suggested that they may contribute as much iron as rivers do.

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