Iron Fertilization Experiment Leads to Massive Phytoplankton Bloom in the Southern Ocean

Summary

Office of Science and the National Science Foundation jointly funded the Southern Ocean Iron Experiment (SOFeX), an oceanographic field experiment to determine the effect of the addition of iron on an area south of New Zealand. The increase in atmospheric carbon dioxide and its potential impact on climate has led marine scientists to study the role of the ocean in carbon sequestration. Microscopic marine plants called phytoplankton are responsible for photosynthetic carbon fixation in the ocean. Phytoplankton are naturally limited by the low levels of iron in the Southern Ocean which surrounds the continent of Antarctica. In January-February 2002, three research vessels fertilized two 15 X 15km study sites with dissolved iron and inert chemical tracers to label the “patches,” (volumes) of ocean that were first fertilized. The iron produced a bright green phytoplankton bloom that could be seen from space by ocean color satellites. Over 100 SOFeX scientists are now engaged in analyzing samples collected from the fertilized areas of the ocean, as well as modeling, and synthesizing the results to determine the ultimate fate of the fixed carbon associated with the phytoplankton bloom. For iron fertilization to serve as a viable carbon sequestration option, the carbon associated with the bloom would need to sink to the deep ocean and be sequestered for hundreds to thousands of years.