Is the ocean pumping iron?

ocean sunset

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About 30 years ago, an oceanographer, John Martin, noticed that large areas of the sea contained ample supplies of nitrogen and phosphorus. He wondered why these nutrients, which fuel plant growth, were not being used by marine plankton.

Martin hypothesized that plankton were unable to capitalize on the available nitrogen and phosphorus because concentrations of another nutrient, iron, were too low.  And it turns out, iron is needed during photosynthesis.

Large-scale experiments have now demonstrated that if we add iron to the ocean’s waters, we can induce a bloom of phytoplankton. Iron is now recognized as a trace nutrient that controls the productivity of the seas. So, where do marine plankton get their iron naturally?

Examining the historical record contained in ice cores taken from Antarctica, scientists find high concentrations of iron dust associated with periods when the Earth was rather droughty. Increasingly, we find evidence that the iron in the sea’s surface waters is derived from desert dust that is transported over long distances.

Dust from Australia feeds the waters of the Southern Ocean around Antarctica.  And, dust from China feeds the open waters of the Pacific. This link between land and sea is another example of our evolving understanding of the global linkages that determine how the Earth functions.

Productivity of fisheries is directly dependent on the productivity of marine phytoplankton.  So, next time you have a seafood dinner, thank the dust of distant deserts for supporting the bounty of the sea.

Photo, taken on November 5, 2008, courtesy of Jeffrey via Flickr.


Earth Wise is a production of WAMC Northeast Public Radio.  Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY, with partial support from the Field Day Foundation.



Earth Wise is a presentation of WAMC Northeast Public Radio and The Cary Institute of Ecosystem Studies Follow us Facebook Twiter RSS Podcast