It's bottoms up for iron at sea's surface

12:18pm, January 2, 2002

Biological activity at the base of the food chain in many regions of the ocean is limited by the availability of dissolved iron. The algae that convert sunlight into food in the sea's top 100 meters or so can't fully use the other nutrients present because there isn't enough iron. Just where the crucial metal comes from is often not known.

An analysis of seafloor sediments obtained off Antarctica suggests that the dissolved iron in surface waters that fuels much of the region's biological productivity comes from deeper waters via upwelling currents.

Many scientists have thought that much of the ocean's dissolved iron comes from dust blowing off the continents, notes Gabriel M. Filippelli, a biogeochemist at Indiana University–Purdue University in Indianapolis.

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