Several times over the past century, scientists and environmental engineers have proposed spreading slurries of dissolved iron into the oceans in order to 'fertilize' the waters and promote vast blooms of marine plants called phytoplankton.
Phytoplankton consume carbon dioxide as they grow, and this growth can be stimulated in certain ocean basins by the addition of iron, a necessary micronutrient.
Though common on land, dissolved iron is often rare in the ocean. Some researchers and commercial interests have proposed to provide that missing nutrient on a large scale in order to create artificial blooms.
Some scientists say that if such blooms grow large enough, they could remove excess carbon dioxide from Earth's atmosphere and carry it down into the deep ocean as organic matter sinks, reducing the impact of greenhouse gases and global warming.
'There are many critical questions that require both better scientific understanding and an improved legal, economic, and political framework before iron fertilization can be considered either effective or appropriate,' said Ken Buesseler, a senior scientist in WHOI's Marine Chemistry and Geochemistry Department and a participant in two iron fertilization experiments at sea. 'The time is right to bring scientists, policymakers, and commercial interests together to inform each other and the public.'
Scientists took a serious interest in the idea in the late 1980s after oceanographer John Martin famously told colleagues, 'Give me half a tanker of iron and I'll give you the next ice age.'
Iron fertilization has since been tested in at least a dozen experiments around the world. The results have varied, but in general, iron fertilizers have been shown to promote plant growth in surface waters.
Still, many researchers remain skeptical about whether the process removes carbon dioxide from the atmosphere for the long term or just for a short time.
Ecological impacts from long-term, large-scale fertilization are also a concern.
WHOI also will host an open, public colloquium on iron fertilization at 2:30 pm on October 19 in the Redfield Auditorium on Water Street in the Village of Woods Hole.