A controversial idea to fight climate change by using iron to manipulate ocean ecosystems probably won’t work, according to a study by researchers at the Massachusetts Institute of Technology.

The study, which was based on computer modeling and published this month in Proceedings of the National Academy of Sciences, looked at adding iron to the oceans as a sort of fertilizer for phytoplankton, the tiny plants and algae that can absorb planet-warming carbon dioxide from the atmosphere.

The researchers’ finding: The world’s oceans appear to have all the iron they need, thank you.

“Iron fertilization cannot have a significant overall effect on the amount of carbon in the ocean because the total amount of iron that microbes need is already just right,” said Jonathan Lauderdale, a research scientist in the university’s department of earth, atmospheric and planetary sciences and the study’s lead author.

David Emerson, a senior research scientist at the Bigelow Laboratory for Ocean Science in East Boothbay, Maine, said the study raised important questions about iron fertilization and its effects.

“The authors of this PNAS paper point out an important potential shortcoming of long-term iron fertilization based on computer model simulations, and these cannot be taken lightly,” he said. “But there are experiments showing that iron fertilization contributed to carbon reductions in the ice ages and those cannot be ignored.”

Dr. Emerson said the concept of iron fertilization required more research that would take “at least one to two decades of work and expenditures in the low billions of dollars.”

Phytoplankton, which uses carbon dioxide for photosynthesis, needs iron to grow. So adding more iron to the oceans, the theory goes, would lead to more phytoplankton and more carbon being pulled from the atmosphere.

The theory, and the field of geoengineering in general, is contentious because many scientists and environmentalists fear that large-scale manipulation of ecosystems could come with large-scale unintended consequences.

In the summer of 2012, George Russ, an American businessman, sprinkled 100 tons of iron dust into the Pacific Ocean off the coast of British Columbia in an ecological venture that outraged scientists and government officials in both Canada and the United States.

There was a temporary increase in plankton growth. But residents close to the fertilized stretch of water later reported more toxic shellfish, dead sea lions and odd crimson-colored plankton.

Those observations correspond with the findings of the MIT study. More iron in the sea would deplete other nutrients, cause plankton death and have negative effects on marine life, the researchers said. 

Shola Lawal is the 2019 Elizabeth Neuffer Fellow at the International Women’s Media Foundation. The fellowship brought her to MIT as a research associate at the Center for International Studies.