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Science & Technology

March 31, 2008
Volume 86, Number 13
pp. 30-33

Fertilizing The Ocean With Iron

Large-scale experiments will determine whether plankton can battle climate change

Rachel Petkewich

THE PRIVATELY OWNED research ship Weatherbird II set sail from Florida in November on a controversial mission: to spread tons of iron over the ocean with the aim of triggering oversized blooms of phytoplankton.

In theory, the chlorophyll-containing marine organisms would snare CO2 from the atmosphere and convert it to biomass, which would then settle in the deep ocean. As an added incentive, entrepreneurs could sell carbon offset credits to individuals or companies that want to balance out their CO2 emissions.

Icebreaker Researchers from India, Germany, and other countries plan to use the RV Polarstern to do a large-scale experiment in the Scotia Sea next year.

But the ship and its crew were called back from the Portuguese island of Madeira last month even before their first experiment could commence. Planktos, the Foster City, Calif., company operating the ship, lost its investors.

The company announced via its website that it had "been forced to indefinitely postpone its ocean fertilization efforts once intended to restore marine plant life and generate ecological offsets for the global carbon credit market" because of "a highly effective disinformation campaign waged by antioffset crusaders."

Saving the world, it seems, is not as simple as tossing some iron into the ocean.

As countries search for ways to deal with human-induced climate change, hundreds of start-up companies like Planktos have devised plans to clean carbon out of the air and make money on credits. The purchases fund projects that reduce emissions of greenhouse gases, such as planting trees or creating plankton "forests."

Fertilizing the ocean with iron is not a new idea for controlling atmospheric CO2, but the discussion has taken on new dimensions now that profit-seeking firms have entered the picture. Environmental groups worried about the long-term effects oppose artificially stimulating blooms. Ocean scientists say more study is necessary to determine whether ocean iron fertilization is even viable.

To address these concerns, academic researchers, with public and private funding, are planning two larger scale studies for next year. In the meantime, the countries that are party to the London convention, the leading global marine environmental protection treaty, are planning to meet in Ecuador in May to continue discussing how to regulate adding iron to the ocean.

Planktos may have folded, but a couple of ocean iron fertilization companies still live. The front-runner is San Francisco-based Climos, which is run by a high-powered mother-and-son team. Dan Whaley, an entrepreneur who launched the travel site GetThere.com, started Climos in 2006. Last year, his mother, Margaret Leinen, an oceanographer with a long career in academic research and administration, left her position as assistant director for geosciences at the National Science Foundation to become chief science officer of Climos.

Leinen says she had spent much of the previous year reviewing papers for the Intergovernmental Panel on Climate Change working groups and wanted to take action. Climos says it will make sure the science works before selling offsets. "We do not think you should presell credits with the anticipation that you will sequester carbon," Leinen says.

Ocean scientists have been thinking about iron's role in oceans, plankton growth, and climate for a long time. The success of sequestration via iron fertilization of the ocean ultimately depends on whether that carbon stays sunk in the deep ocean.

Data from NASA SeaWIFS Project
Testing The Waters Several groups conducted 12 small-scale iron fertilization experiments (white dots) in various parts of the ocean between 1993 and 2005.

Phytoplankton already fix 50 billion tons of carbon per year and naturally grow when iron-containing dust drifts into ocean waters. Blooms form in stages at the surface of the ocean and die off.

Single-celled phytoplankton are the first organisms to develop in a bloom. To grow, they need light and trace nutrients such as iron, which transports electrons during photosynthesis. Larger species of phytoplankton such as diatoms can emerge and make the bloom bigger. Ocean scientists say diatoms generally sink. The smaller phytoplankton are eaten by zooplankton. Their fecal material, sometimes aggregated with organic matter, can sink into the deep ocean.

Circa the 1930s, scientists suggested that iron deficiency could account for areas of the Antarctic Ocean with scarce phytoplankton. Iron available for phytoplankton growth is scarce in the ocean because of its low solubility in oxygenated seawater.

DECADES LATER, oceanographer John H. Martin, then-director of Moss Landing Marine Laboratories in Moss Landing, Calif., who is credited with calling attention to the idea that iron plays a large role in the biogeochemistry of the ocean, observed that iron concentrations were likely higher in the ocean during glacial periods, when levels of atmospheric CO2 were lower.

Other research suggested that atmospheric CO2 could have been lowered during certain periods by the ocean's biological pump, a collection of biological processes that transport carbon from the ocean's surface to the deep ocean.

By the late 1980s, scientists agreed that increased amounts of CO2 in the atmosphere were linked to climate change. Martin then proposed the "iron hypothesis," a pioneering notion that adding iron to the ocean would essentially activate the biological pump by fueling phytoplankton blooms to remove CO2 from the air.

Martin's off-the-cuff quip—"Give me half a tanker of iron, and I'll give you an ice age"—has been widely quoted. His enthusiasm caught the attention of the National Research Council, which released a report estimating that phytoplankton blooms could sequester a whopping 2 gigatons of carbon for less than $1 billion annually. Recommendations issued from two NRC workshops in the late 1980s called for an international iron enrichment experiment.

Martin died in 1993, just months before the first experiment. By 2005, ocean scientists had conducted a dozen small-scale field experiments to test the iron hypothesis. Each study was conducted in the open ocean, which is hundreds of nautical miles from coasts, and required between 1 and 3 metric tons of iron that was dispensed from a tanker as liquid iron sulfate and dispersed in 100-km2 patches. (Sulfate is one of the most abundant natural ions in the ocean.)

Through these experiments, researchers verified that iron can stimulate growth of phytoplankton, which can in turn "affect the biogeochemical cycles of carbon, nitrogen, silicon, and sulfur and ultimately influence the Earth climate system" (Science 2007, 315, 612). But the question remains: Will fertilizing the ocean with iron ultimately drive carbon deep into the ocean, where it will remain sequestered for 100 years or more?

Last September, dozens of scientists, businesspeople, and regulatory officials spent two days at the Woods Hole Oceanographic Institution (WHOI) debating the efficacy and safety of large-scale fertilization. They concluded that large-scale experiments are needed to answer scientific questions and inform policy and business decisions.

Sixteen of those scientists outlined the essentials for such experiments (Science 2008, 319, 161). They pointed to measuring the subsurface ocean to verify the fate of fixed carbon, characterizing changes to oxygen distribution, and observing how non-CO2 greenhouse gases such as methane and nitrous oxide cycle. The long-range effects of the experiments need to be modeled and monitored. Finally, they noted that newer models show that oceans with high nutrient levels "would be unlikely to sequester more than several hundred million tons per year." Unlike earlier estimates, this figure suggests that ocean iron fertilization alone cannot address the world's growing carbon problem. So scientists must ask how ocean iron fertilization stacks up against doing nothing, they say.

"We are already geoengineering the world by doing nothing," says Ken Buesseler, a biogeochemist at WHOI who supports large-scale experiments.

Ocean researchers are currently planning two large-scale experiments for 2009 to learn the fate of organic matter produced by iron fertilization. Victor Smetacek, a professor of biological oceanography at the Alfred Wegener Institute for Polar & Marine Research (AWI) in Germany, and chemical oceanographer S. W. A. Naqvi of the National Institute of Oceanography in Goa, India, are leading an expedition in collaboration with scientists from Italy, Spain, France, and Chile called Lohafex. (Loha is Hindi for iron). It is slated to sail January through March in the Scotia Sea, which is located in the Southern Ocean between the southeastern tip of South America and Antarctica.

Although unpublished results from the European Iron Fertilization Experiment led by Smetacek in February and March 2004 revealed that organic matter did sink to depths of a few kilometers in the subpolar South Atlantic Ocean, the upcoming expedition aims to analyze the conditions under which such material is exported into the deep ocean instead of staying near the surface, Naqvi says.

Chain Gang Single-celled phytoplankton range from slightly less than 1 μm to nearly 1 mm in length and sometimes form chains, like these diatoms.

They plan to fertilize the core of a 2,000-km2 ocean eddy with up to 20 metric tons of ferrous sulfate, Naqvi says. They will then monitor the patch's characteristics for about seven weeks, making standard oceanographic measurements such as temperature and nutrient levels. Sediment traps, as well as measurements of a natural thorium isotope used to track sinking carbon, will indicate how much carbon material falls from the surface. They will also track production of phytoplankton and sinking algal cells, as well as zooplankton and krill.

India's Council of Scientific & Industrial Research (CSIR) has provided the bulk of the funding for Lohafex. Additional ship costs, running at approximately $4 million for AWI's icebreaker RV Polarstern, will be shared equally between CSIR and AWI.

With an eye to eventually selling carbon credits, Climos is planning to bankroll a second experiment for academic scientists. They have raised $3.5 million from investors, but Leinin says they will need to raise more. She adds that the scientific details are still in the works, but they are actively considering sites in both the Atlantic and Pacific Ocean. She says new autonomous underwater vehicles are likely to be used to reduce costs for monitoring the large-scale experiments.

Commercialization, however, would mean fertilizing the ocean on a grander scale and additional uncertainty. If huge portions of the ocean were fertilized for a long time, the ocean's interconnectivity could also trigger changes in the ocean's pH and productivity, reduced oxygen content of the deeper ocean, or enhanced emissions of nitrogen oxide from the oceans into the atmosphere. Indirectly, ocean iron fertilization could affect the health of coastal ecosystems. "Ocean fertilization on a scale large enough to have a significant influence on atmospheric CO2 would have indirect effects that are very difficult to predict and some important ones that may not be possible to measure," says John J. Cullen, a professor of biological oceanography at Dalhousie University in Halifax, Nova Scotia.

Beyond the scientific uncertainty lie simultaneous debates about ethical use of the oceans and how that translates to regulations.

Environmental groups have concerns. Lisa Suatoni, a senior scientist with the Natural Resources Defense Council, says questionable efficacy, a host of largely unstudied potential side effects, and the challenges of verification make commercial-scale ocean iron fertilization a risky venture for carbon markets and marine ecosystems alike.

Regulators are struggling because large-scale ocean iron fertilization doesn't clearly fall under any existing laws. Some of the smaller scale experiments required specific permits, whereas the U.S. cruises, for example, were government-funded research and therefore did not have to go through a separate approval process.

The open ocean falls within the scope of international law, particularly the 1972 London convention, one of the first global agreements to protect the marine environment from human activities. In force since 1975, it regulates ocean dumping and guards against detrimental commercial use of the ocean. The 1996 London protocol, which was designed to modernize the convention and went into effect in 2006, incorporates a large number of additional restrictions on dumping. An amendment to the protocol that went in to effect in February allows storage of CO2 under the seabed. Permits and impact assessments are required prior to any authorized dumping activities under both agreements.

THE U.S. IS ONE of 82 states party to the London convention but is not one of the 33 parties to the London protocol. Climos has talked with the Environmental Protection Agency, which is the U.S. agency enforcing the London convention, about what could be involved with getting a permit for ocean iron fertilization projects.

At a November meeting of the London convention/protocol that addressed ocean iron fertilization, among other issues, the parties decided that because the iron would promote biological growth, ocean iron fertilization could have impacts on human and marine resources. The official statement declared that large-scale operations are currently not justified and urged states to use caution when considering proposals. The concern over large-scale operations would seem to refer to commercial ventures and the upcoming research expeditions, but the topic is still open for discussion, says David Freestone, a senior legal adviser for the World Bank. The parties will continue to address the issues in May at a meeting in Ecuador.

Other discussions about ethics are afoot. For example, Climos proposed a code of conduct for operating ocean iron fertilization projects, posted it on its website in September, and asked for feedback from the scientific community. The community suggested, for example, that the researchers ensure the iron sulfate is pure.

Climos' approach sits better with the scientific community than Planktos'. Cullen says that Planktos did not develop a relationship with the science community and that it had a history of unsubstantiated claims. But, he notes, Climos seeks guidance from scientists and adheres to ethical conduct, including a commitment to assessing secondary effects.

If ocean iron fertilization doesn't sequester carbon, Leinen says, "nobody on the commercial side will be doing it. If it does, I think it then brings up another set of questions that relates to the impacts." After all, Leinen adds, "we only have one ocean."

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