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Massive Underwater Iron Plume Billows from Atlantic Hydrothermal Vents

First Posted: Aug 19, 2013 02:44 PM EDT

Scientists have made an amazing discovery deep beneath the waters of the South Atlantic Ocean. They've found a vast plume of iron more than 600 miles long billowing from hydrothermal vents.  The finding not only calls into question past estimates of iron abundances, but also may challenge assumptions about iron sources in the world's seas.

The researchers actually didn't set out to find iron in the Atlantic. Instead, they wanted to map chemical composition and microbial life along a route between Brazil as Namibia. As they traveled this route by ship, they sampled the seawater at frequent intervals and multiple depths. This allowed them to gather information about the different areas, learning more about the chemical composition of the ocean.

Along their route, the researchers passed over the Mid-Atlantic Ridge. This band of mountains and valleys run along the Atlantic Ocean floor from the Arctic to the Antarctic. Along this ridge are hydrothermal vents, fissures in the Earth's crust. Yet these vents have yet to be extensively studied since slow-spreading ridges are thought to be less active than fast-spreading ones.

After analyzing their samples, though, the researchers found extremely high levels of iron and manganese. Once they mapped where these samples came from, they found that the samples formed a distinct plume.

"We had never seen anything like it," said Mak Saito, one of the researchers, in a news release. "We were sort of shocked--there's this huge bull's-eye right in the middle of the South Atlantic Ocean. We didn't quite know what to do with it, because it went contrary to a lot of our expectations."

The findings actually seem to show that, in contrast to previous beliefs, slow-spreading ridges aren't iron poor. In addition, it raises questions about the use of helium as an indicator for iron flux in hydrothermal vents. Since iron is a critical element for ocean life, this has huge implications for future studies.

"We need to understand where iron is in the ocean and where it's coming from to understand the role of iron in the marine carbon cycle with any confidence," said Saito in a news release.

Currently, the researchers plan to conduct future studies that may reveal the exact shape and extent of the plume. This could show exactly how much of its iron and other micronutrients persist and rise to the surface, which could reveal a little bit more about the ocean's nutrient cycle.

The findings are published in the journal Nature Geoscience.

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