Only mother nature knows how to fertilize the ocean

Quirin Schiermeier in Nature: Blooms of algae created by pumping nutrients into the ocean can suck up at least ten times more carbon dioxide (CO2) from the atmosphere than was previously thought. But the findings lend no support to controversial schemes to encourage such blooms in order to reduce global warming, the authors warn.

The conclusion comes from a survey of a large, annually recurring natural algal bloom near Kerguelen, an archipelago halfway between South Africa and Australia. Natural vertical mixing of the ocean there steadily supplies iron and other nutrients from sediments at the ocean floor to the surface waters, encouraging phytoplankton growth. This growth converts carbon in the air (as CO2) to organic matter, thus reducing the amount of greenhouse gas in the atmosphere and alleviating climate warming.

Stephane Blain, a chemical oceanographer at the Oceanography and Biogeochemistry Laboratory in Marseille, France, led a 47-strong international team to investigate this bloom in detail in early 2005. Their results show that the ability of such blooms to suck up CO2, and to carry that carbon to the ocean floor when the organisms die, is much greater than previous field studies had suggested.

…Scientists have long proposed that 'seeding' such oceans with extra iron could provide an eco-friendly means of reducing CO2 in the atmosphere; this notion spurred the many experiments in which researchers tried adding iron to small patches of sea.

….Blain's study shows that mother nature can do much better at fertilizing the ocean than mankind. The rate at which CO2 is sucked up seems to be so great at Kerguelen because the iron is being supplied slowly and continuously, and because the ecosystem is rich in other biological and chemical ingredients needed for such a bloom….

Mount Ross on Kerguelen, shot by B.navez, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 2.5 Generic license