U of Minnesota-led study reveals mysteries of deep-sea nutrients

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, a new study led by a University of Minnesota scientist shows.

Iron holds a crucial place in the aquatic food chain, but is extremely scarce in many environments. "There is a lot of iron released to the ocean from deep-sea hydrothermal vents," said Brandy Toner, an assistant professor in the University of Minnesota's department of Soil, Water and Climate. "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." Toner led the research on iron chemistry as a postdoctoral researcher at the Woods Hole Oceanographic Institution in Massachusetts.

The study is being published Feb. 8 in the online edition of Nature Geoscience and for the first time connects life near the ocean's surface to what happens at extreme depths and pressures. Previously, the two had been assumed to operate independently.

Researchers 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. Unlike the iron that lands in the ocean through wind or river water, iron from the deep sea isn't rusty, which means it might provide more nutrients for sea life.

The research applies a soil chemistry perspective to questions about iron in marine waters, Toner says. "The discovery highlighted in this paper will change the ways scientists think about iron and carbon cycling in the deep waters of the ocean."

The study was funded by NASA, the U.S. Department of Energy and the National Science Foundation. It included scientists from the University of Southern California as well as the Lawrence Berkeley National Laboratory and the Woods Hole Oceanographic Institution.