California businessman Russ George made headlines in 2012 when he, in cooperation with a group from a Native Canadian community, dumped more than 100 tons of iron sulfate into the Pacific, some 200 miles off shore. The iron then triggered a bloom of plankton. He apparently didn’t ask anybody’s permission, violated two United Nations conventions, and was widely condemned for taking on such a large project, a type of geoengineering, to alter the environment as he saw fit.
Iron causes blooms of plankton to form because the element is required for the tiny plant-like cells to live, and is usually only present in small quantities at the surface. Places with strong upwelling currents–such as areas off the U.S. West Coast–often have higher levels of iron brought up from the deep ocean, and for that reason often have abundant plankton and sea life. George’s idea was to create this bloom to both absorb carbon dioxide (the plants need this greenhouse gas to grow) and to provide food for local salmon stocks. After the tiny cells capture carbon dioxide as they’re growing, they eventually sink to the bottom and die, removing the gas from the atmosphere.
A new study in the Journal of Plankton Research suggests that the plan may have actually worked better than previously thought to increase the number of crustacean zooplankton upon which young salmon feed. And, in turn, the number of salmon in this area has approximately doubled since 2010. But it can’t be proved that there is a causal relationship between the iron seeding experiment and the increased numbers of fish. Historically populations of fish have varied for many reasons, some of them unknown. It also isn’t clear how much carbon dioxide the experiment sequestered.
Wilf Luedke, Canada’s chief of salmon stock assessment for the south British Columbia coast, told Andrew Revkin at the New York Times that he has nothing against careful tests of deep-sea iron fertilization, but worries that debate out this geoengineering solution could distract from more proven methods for increasing salmon numbers and absorbing carbon dioxide, such as “conserving carbon-absorbing eelgrass beds in coastal inlets and continuing to restore salmon rivers and streams long beset by dams, careless logging and encroaching development.”
“We can’t fix oceans in the short term,” Luedke said. “But how we deal with rivers and watersheds, that we can fix right now.”
But there is other evidence that iron fertilization isn’t all that geoengineering supporters might hope. There have been natural occasions when levels of iron have shot up, for example when the Icelandic volcano Eyjafjallajökull erupted in 2010, spewing iron-rich ash into the ocean. Scientists studied the plankton blooms triggered by the eruption, but found that they soon died (because they ran out of another nutrient, nitrogen) and didn’t absorb much carbon dioxide.