Why Ocean Fertilization Could Actually Hurt Marine Health

Seeding our water with iron could hinder biodiversity.
The consequences of iron seeding may be counterproductive to fighting greenhouse gases over the ocean. (Photo: George Hanf/Getty Images)
Jun 20, 2013· 1 MIN READ
A staff writer for LiveScience, Doug has written for the NYTimes.com. He lives in New York City.

Well, isn't this iron-ic: Putting iron into ocean waters to stimulate the uptake of carbon dioxide—a geoengineering scheme that’s been investigated for its potential to help combat global warming—may have unintended consequences that could limit its effectiveness, if not render it counterproductive.

A recent study published this month in the journal Nature Communications, found that the outer shells of diatoms, a widespread type of algae, contain much higher levels of iron than previously documented.

They could act to "hog" iron in sea water, leaving less of it for other types of algae, according to Julia Diaz, a study co-author and researcher at the Woods Hole Oceanographic Institution in Massachusetts.

The idea behind ocean fertilization is relatively simple: put iron into the ocean, and let the algae bloom. This purposeful introduction of nutrients is, in theory, supposed to increase marine food production and remove carbon dioxide from the atmosphere. After the bloom, the algae die and take their carbon with them to the bottom of the ocean, where it may remain for eons, not adding to the greenhouse effect.

But it's a bit more complicated than that, according to Diaz. The study looked at the levels of iron in diatoms collected from the Southern Ocean, finding significant and surprising levels of the metal. Diatoms have been found to be more plentiful after ocean fertilization experiments, meaning they could be taking up this excess iron.

"If that's the case, that makes that iron unavailable to other organisms," Diaz tells TakePart. "And those other organisms may be more capable of drawing down carbon dioxide from the atmosphere."

While it's a bit of a stretch to suggest the ocean fertilization may release carbon dioxide in certain circumstances, it's not impossible. The ocean relies on a balance of phytoplankton, tiny-plant like cells that harness carbon dioxide, and bacteria than can eat these plants and release the gas.

Nobody knows exactly how ocean fertilization may affect this balance in the future. This study suggests that diatoms' ability to "hog" the carbon dioxide is one more complicating factor.

"It's not clear what the long-term effects of iron fertilization would be," Diaz says. "We don't know what to expect. It could be dangerous—it might not do what we want it to do."

Government-backed programs have tested ocean fertilization a handful of times in the past. Like most geoengineering solutions, it's generally regarded by scientists as unpredictable, and unwise to be implemented without further testing, if at all.

Last summer, a group dumped 100 metric tons of iron dust into the ocean off the coast of British Columbia. The action led to an algae bloom, and prompted international backlash and condemnation against them for using an unproven method on an already fragile ocean.

The CEO of the company that conducted the "experiment," the Haida Salmon Restoration Corporation, was fired last month. But the company said that it still supports the concept for its potential to feed salmon and sequester carbon.

Are you sold on the potential benefits of ocean fertilization, or do you think it's too experimental? Let us know in the Comments.