February 8, 2009

Researchers Discover Iron Deep In The Ocean

A team of scientists led by the University of Minnesota has discovered that iron dust, the rare but necessary nutrient for most life, can not only be washed into the ocean from rivers or blown out to sea, but it can bubble up from the depths of the ocean floor.

The study, published in the journal Nature Geoscience, connects life at the surface to events occurring at extreme depths and pressures"”two worlds long assumed to have little interaction.

Brandy Toner, an assistant professor in the University of Minnesota's Department of Soil, Water and Climate, said large amounts of iron are released into the ocean from deep-sea hydrothermal vents.

The group found that organic compounds capture some iron from hydrothermal vents, enabling it to be carried away in seawater.

"The key to understanding where the iron will travel and whether it will be accessible to life depends on the chemical form of the iron; at the sea floor, we're finding forms of iron we didn't expect to see."

The research team used remote devices to collect particle samples from parts of the Pacific Ocean where underground volcanoes are common. The volcanoes create hydrothermal vents that spew iron, which in turn is captured by organic compounds that carry the iron away in seawater.

Iron from the deep sea isn't rusty, which means it might provide more nutrients for sea life.

Katrina Edwards, one of the researchers from the University of Southern California, said the metal's purity has practical value.

"Aquatic organisms metabolize pure iron much more easily than its rusted form," Edwards said.

She said they are still unsure exactly how much captured iron floats into surface waters, but any that does would nourish ocean life more efficiently than the oxidized iron from regular sources.

"This is one potential mechanism of creating essentially a natural iron fertilization mechanism that's completely unknown," Edwards said.

Many marine scientists have called for iron fertilization because of the metal's crucial place in the aquatic food chain. Iron is the limiting nutrient in most parts of the oceans, meaning that its scarcity is the only thing standing in the way of faster growth.

Toner believes the research applies an important soil chemistry perspective to questions about iron in marine waters.

"The discovery highlighted in this paper will change the ways scientists think about iron and carbon cycling in the deep waters of the ocean."


Image Caption: Iron spewed from hydrothermal vents and carried away by seawater does not rust. Credit: Nicolle Rager-Fuller, National Science Foundation


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