For the past 15 years, scientists have been exploring a novel new way to combat global climate change. The technique, known as ocean iron fertilization (OIF), uses iron to spur the growth of oceanic algal blooms, which, theoretically, could draw tons of carbon from the atmosphere via photosynthesis. After a decade of experimenting, however, many scientists remain concerned about the practicality, efficacy, and ecological safety of large-scale deployment.

Understanding Ocean Iron Fertilization

Two decades ago, a scientist discovered that dumping iron, an important nutrient, into the right ocean waters could trigger vast algal blooms, which absorb large quantities of carbon dioxide from the atmosphere as they grow. Laboratory experiments suggest that for every ton of iron added, 30,000 to 110,000 tons of carbon could be drawn from the atmosphere. If applied to the entire Southern Ocean, these estimates indicate that OIF could remove up to 25 percent of annual anthropogenic CO2 emissions.

Experiments Lead Scientists to Doubt Efficacy and Safety

However, 12 small-scale ocean experiments conducted since 1993 have revealed less promising results. Once absorbed by the algae, only a minute fraction of carbon will descend to the ocean floor in the form of dead cells and fecal matter, where it will be sequestered in deep ocean sediments for millions of years. The rest will be quickly recycled back into the atmosphere when larger organisms consume the algae or will be transported by ocean currents to middle-depth waters, where the carbon will remain for a few decades at most. A few decades of sequestration might buy society enough time to initiate more fruitful strategies to mitigate climate change but certainly will not spell long-term relief.

Furthermore, scientists worry about the potential ecological implications of scaling up OIF. Overall, ocean ecosystems are poorly understood relative to their terrestrial counterparts, and tampering with the base of the food chain could yield undesirable consequences. Algae-choked surface waters could block sunlight to deeper waters, deplete surrounding waters of vital nutrients, warm surface waters and change circulation patterns. Scientists can only guess at how these changes might affect fish stocks and other marine mammal populations.

Locations of 12 Ocean Iron Fertilization Experiment Sites



Source: Woods Hole Oceanigraphic Institute

Potential Profits Drive Continued Research

Despite these concerns, research for OIF continues and is increasing in scale. Prospective experiments are emerging that will use 100 times more iron than has previously been tested. Proponents of these experiments argue that improved scientific understanding is needed to assess OIF's true potential, and by scaling up incrementally, they can detect and avoid undesirable side-effects. Private companies, rather than scientists, appear to be driving this growth. If emerging international carbon trading markets were to allow for iron fertilization offsets, OIF could have a potential value of $100 billion over the next century according to a recent economic analysis.

The high seas are not owned by any individual country and the international treaty governing ocean dumping and pollution has no enforcement power, so companies pursuing OIF, most notably Planktos and Climos, face few restrictions. However, even if these companies are able to yield modest carbon reductions from their projects, it remains clear that more solutions must be found to prevent dangerous levels of global warming.

RELATED LINKS:

Woods Hole Oceanographic Institute

"Will Ocean Fertilization Work?" (Article in Science)

"Ocean Iron Fertilization--Moving Forward in a Sea of Uncertainty" (Article in Science)

EarthTrends

Statistics and data on coastal and marine ecosystems

"Nutrient Overload: Unbalancing the global nitrogen cycle"

"Ocean Acidification, the Other Threat of Rising CO2 Emissions"