Iron that goes to the sea

An initiative to monetize carbon dioxide-eating algae is angering scientists

By Suresh Basu

Researchers have been debating for a long time whether dumping iron into the sea could slow climate change. Iron encourages the growth of tiny algae called phytoplankton that absorb carbon dioxide (CO2) dissolved in the ocean during their photosynthesis process. This process in turn draws atmospheric CO2 into the water near the surface. Most scientists doubt that fertilizing the water with iron will result in greater carbon sequestration. But a commercial company called Planktos from Foster City, California is promoting such programs. Her latest goal: 10,000 square kilometers in the Pacific Ocean, in the equatorial region, 600 km west of the Galapagos Islands. There is no doubt that this is the most ambitious plan to date, and the most controversial, for sowing iron in the sea.

The phytoplankton algae are comparable in the amount of CO2 they fix in the process of photosynthesis to all terrestrial vegetation in the world. Although most of the fixed carbon returns to the water after a week when the algae die, up to a fifth of the biomass sinks to deeper water layers and traps the carbon in the seawater. To carry out photosynthesis, the phytoplankton need tiny amounts of iron. In the equatorial Pacific, most of the metal comes from sandstorms blowing from the Gobi and Taklimactan deserts in central Asia.

The Planktus company cites a study by NASA and the American Meteorological Service (NOAA) and claims that the amount of iron reaching the equatorial Pacific Ocean has decreased by 15% since the early 80s, probably due to a change in the wind regime and a decrease in the number of sandstorms. As a result, the company concludes, the phytoplankton population shrank by 6% and CO2 absorption by 3%. Through iron fertilization, the company wants to restore the supply of the metal and the phytoplankton population that existed before 1980. This will result in "the absorption of 70% of the current carbon dioxide emissions," claims Planktus' marketing director, William Coleman.

On the other hand, John Cullen, an oceanographer from Dalhousie University does not believe that a smaller population of phytoplankton captures less CO2. "Successful" fertilization, he explains, will lead to the sedimentation of phytoplankton-derived biomass into deeper waters, and together with that, the nutrients it absorbed will also sink. This will lead to the elimination of chlorophyll (phytoplankton) and with it the iron. Such decreases in the amount of phytoplankton therefore serve as a sign that carbon has been sequestered.

In any case, most researchers doubt that adding iron will result in a shift of carbon to the oceans. A dozen experiments have indeed shown that the addition of iron leads to the prosperity of the phytoplankton, but the question of whether in the long term this will lead to the capture of more carbon in the deep waters remains open. In one of the experiments, "less than 10% of the excess fixed carbon managed to reach a depth of only 120 meters," says oceanographer Philip Boyd from New Zealand's National Institute for Water and Atmospheric Research. In any case, strong upwelling currents, which are common in the equatorial Pacific Ocean, will likely lead to the re-release of the trapped carbon into the atmosphere within a few years, says Anthony Michaels, an oceanographer at the University of Southern California.

Other data also contradict Planktus' claim that less iron reached the sea from Asia. An analysis of air samples from Midway Island, the only station in the Pacific Ocean that collects field data on dust transport, "did not show any downward trend [in dust coming from Asia] from 1981 to 2001," says Joseph Prospero, of the University of Miami attached to the Midway Observatory. Moreover, Robert Davis, an atmospheric scientist at Texas A&M University, says that "there is no solid evidence that there has been any long-term change in the regime of the winds blowing from the Asian highlands."

The reduction in the phytoplankton population, if it is indeed real [see frame on the right], may not be related at all to the iron content in the area. Natural cycles lasting decades, such as El Niño and the Pacific Oscillation that occurs every decade, may lead to fluctuations in the algae population, as shown in a study conducted in 2006 by marine algae expert Michael Behrenfeld from Oregon State University and his colleagues.

"Anyone who claims that there is less iron in the oceans today than 100 years ago is making wild assumptions, because we have no data to confirm such a claim," claims Boyd, who served as the chief scientist on two of the 12 experimental voyages to seed iron. Boyd and others argue that Planktus selects only the data that suits it, and that it has difficulty organizing a recognized team of scientists to provide it with the necessary confirmation of the project's scientific validity.

Even researchers who view the idea of ​​fertilizing with iron favorably, such as senior scientist Ken Johnson of the Monterey Bay Marine Aquarium Research Institute, disapprove of Planktus' project. "I would like a non-profit agency to do this research," he says. Planktus' economic incentive is its plan to sell carbon emission credits at the expense of the CO2 that, according to the company's calculations, will be captured through the growth of phytoplankton. These credits will allow buyers to exceed the agreed limits for CO2 emissions. On Planktus' website, the company even invites individuals to pay the company to "reduce" their carbon footprint on the environment.

Despite the criticism, and despite the protest of the American government and environmental protection groups, such as the World Conservation Organization WWF, Planktus stands by its opinion. During the fall of 2007 it is supposed to spill about 50 tons of iron into the equatorial Pacific Ocean. In the absence of a global framework for verifying the amount of carbon that will be captured, Planktus may be sowing the seeds for a scientifically dubious, but profitable business.

Prosperity or bankruptcy?
To justify the fertilization project in the equatorial Pacific Ocean, Planetectos cites a 2003 NASA and US Weather Service report that showed a 6% decrease in CO2-consuming phytoplankton populations. However, later studies concluded exactly the opposite. David Antoine and his colleagues from the marine laboratory in Villefranche in France reanalyzed the same data and found a 37% increase in the chlorophyll level (and hence also in the phytoplankton population). This increase is consistent with field measurements conducted over almost 20 years at a research station in the tropical North Pacific, showing a 50% increase in the phytoplankton population.

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