Through photosynthesis, these tiny, free-floating aquatic plants can convert carbon dioxide to organic carbon, and there appears to be a prehistoric relationship between iron in the ocean and atmospheric levels of carbon dioxide.
Burke Hales, an assistant professor in the College of Oceanic and Atmospheric Sciences at Oregon State University, is one of a number of scientists who collaborated on a new study which involved field research in the ocean near Antartica and will be published Friday in the journal Science.
He described the research as "tremendously successful" because it very clearly shows an induced biological response in the oceans to fertilization with iron.
"During the glacial periods, atmospheric carbon dioxide, or CO2 levels decrease substantially, while during interglacial periods, such as we are now in, those levels increase," said Hales. "There is also a striking inverse relationship between implied, historical iron fluxes to the ocean and atmospheric CO2 concentrations. These relationships suggest some sort of feedback system between iron and CO2 levels during glacial periods that keep the temperature low."
The carbon cycle is a complicated system of causes and effects that are not completely understood, but researchers have long suspected that the oceans are the main regulator of the Earth's atmosphere, said Hales. For example, during the ice ages more of the Earth's water is locked up in glaciers, creating arid, windy conditions and a lot of dust. This iron-rich dust is blown out to sea, stimulating productivity of phytoplankton throughout the world's oceans and reducing CO2 levels.