For more than a dozen years, researchers have been fertilizing small patches of the world's oceans with iron to see if they could make the floating plants called phytoplankton flourish into massive blooms that would absorb carbon dioxide, the worst planet-warming greenhouse gas in the atmosphere.
The idea was that the absorbed carbon would sink to the ocean bottom and remain there essentially forever. Many experts have hailed the idea as one surefire solution to the problem of global warming.
Now a vexing new issue has risen to challenge the whole concept: A major species of plankton that produces an environmental poison known to threaten fish life as well as humans would pose a greater environmental threat when fertilized with iron, according to a team of American and Canadian scientists.
Their findings, published Monday in the online edition of the Proceedings of the National Academy of Sciences, suggest that any massive effort to fertilize ...