( A new study has found that large segmen...)Iron critical to ocean productivity, carbon uptake

As a result, past interpretations of satellite chlorophyll data may be inaccurate, the researchers say, and the tropical Pacific Ocean may photosynthesize 1-2 billion tons less atmospheric carbon dioxide than was previously thought. Global ocean carbon uptake is estimated at 50 billion tons, so the reduction in the estimate of the uptake is significant ?about 2 to 4 percent.

Results of the study were published this week in the journal Nature.

When stressed by a lack of iron, phytoplankton create additional pigments that fluoresce, or light up, unlike normal pigments, according to lead author Michael J. Behrenfeld, a research scientist in Oregon State University's Department of Botany and Plant Pathology. Unfortunately, he added, satellite imagery could not readily distinguish that difference.

"It's really a fascinating process," Behrenfeld said. "When phytoplankton species make these extra pigments, they don't use them right away ?they bank them. Then when they get an infusion of iron, they just take off. They don't have to wait to begin dividing and growing. But that green color wasn't an indication of health, it was an indication of stress from a lack of iron."

The study is also important because it looked at the availability of iron throughout the tropical Pacific Ocean instead of small portions of it. Behrenfeld and his colleagues looked at 12 years of fluorescence data taken along 36,000 miles of ship tracks throughout the tropical Pacific. They now have a "fluorescence fingerprint" of which parts of the ocean are iron-stressed, as well as which parts suffer from lack of nitrogen ?another key element to ocean productiv
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Source:Oregon State University