Seeding Oceans Might Not Lock Up Carbon

Trying to stop global warming with super-blooms of carbon-absorbing algae in the oceans might not work as planned, according to new research published in the Journal of Geophysical Research.

Scientists from Stanford University and Oregon State University conducted their study to test whether "seeding" the oceans with iron or other nutrients could encourage large blooms of algae that naturally absorb carbon dioxide from the atmosphere during photosynthesis. Proponents say the strategy could remove excess carbon dioxide and lock it away deep in the oceans, where algae sink after dying.

Using complex global models, however, the researchers found that might not be the case. Instead, they discovered that when algae populations were largest in the summertime, the amount of carbon sinking to the deep ocean was at its lowest.

"This discovery is very surprising," said Michael Lutz, lead author of the study and now a faculty member at the University of Miami's Rosenstiel School of Marine and Atmospheric Science. "If, during natural plankton blooms, less carbon actually sinks to deep water than during the rest of the year, then it suggests that the Biological Pump leaks."

Lutz added, "Ocean fertilization schemes, which resemble an artificial summer, may not remove as much carbon dioxide from the atmosphere as has been suggested because they ignore the natural processes revealed by this research."

While some say previous ocean fertilization experiments haven't locked away carbon because they didn't have long enough to work, Lutz says nature might simply have another way of dealing with extra-large blooms of algae.

"A bloom is like ringing the marine ecosystem dinner bell," he said. "The microbial and food web dinner guests appear and consume most of the fresh algal food."

That means more carbon is "recycled" in shallow water rather than sinking deep undersea.

"(It) makes sense if you consider how this ecosystem has evolved in a way to minimize loss," Lutz said.

Rising levels of carbon dioxide in the atmosphere, thanks mainly to the burning of fossil fuels, are contributing to a growing greenhouse effect around the globe. Atmospheric concentrations of carbon dioxide are now at the highest ever measured since the beginning of the Industrial Age, and continue to increase annually.

University of Miami's Rosenstiel School of Marine and Atmospheric Science, "New Research Discredits a $100 Billion Fix to Global Warming." URL: (http://www.rsmas.miami.edu/pressreleases/20071129-lutz.html)