"Nitrogen and phosphorus are nutrients that come up from the ocean bottom to feed the upper water column," Behrenfeld said. "Iron, on the other hand, can come from the deep or from the air, but it also enters the ocean through dust deposited by the wind. Windstorms blowing sand and dust off large deserts are a major source of iron for the world's oceans.
"It's like dumping a load of Geritol or some other iron supplement into the water."
Three large areas appear limited by a lack of iron, the researchers say ?the southern ocean around Antarctica, the sub-arctic north Pacific below Alaska, and a huge area in the tropical Pacific centered on the equator. With their newfound knowledge of fluorescence, the scientists believe they now can use satellite imagery to identify specific areas that are iron-stressed ?and how they respond to changes such as the sudden influx of iron from a windstorm.
"It turns out different places in the ocean are missing different nutrients," said Robert Sherrell, a scientist from Rutgers University and a co-author on the study. "The new fluorescence technology now allows us to tell which combination of nutrients is stressing the phytoplankton."
Behrenfeld said the presence of iron stress in the ocean links phytoplankton to the climate through changes in terrestrial-based dust deposited in the ocean, but it is too early to tell if there is an impact of recent climate change on iron-stressed populations because the satellite data record is too short.
"But now we have the tools to determine that," he emphasized.
The northern portion of the tropical Pacific is more nitrogen-stressed and doesn't have the "false greenness," according to Behrenfeld.
The researchers are creating new models of carbon cycling using NASA satellite imagery which they have calibrated using their ship-based measurements of fluorescence.
The role of the ocean in the global carbon cycle is critical ?a
Source:Oregon State University