Pouring iron into oceans may combat global warming by feeding carbon dioxide-gobbling algae, but those algal blooms could become fountains of neurotoxin.
According to a small-scale test, iron-enriched waters favor the growth of Pseudonitzschia, an algae that pumps out brain-damaging domoic acid.
"The toxin per cell increases, and there's an increased success against other species," said oceanographer William Cochlan of San Francisco State University, co-author of the study, published March 15 in the Proceedings of the National Academy of Sciences. Pseudonitzschia "is out there in the most pristine environments. They produce low levels of toxin, so they're not harmful. But if you add iron, and these cells proliferate, and produce more toxin per cell, then you have a problem."
Oceanic iron fertilization is one of many proposed, planet-scale engineering solutions to climate change. Others include shrouding Earth in sun-reflecting aerosol particles, manufacturing CO2-absorbing artificial trees, and pumping CO2 into underground reservoirs.
Critics say these geoengineering schemes are untested, unpredictable and could have disastrous consequences -- if, that is, they even work. Proponents say geoengineering should at least be considered, if only as a last-ditch tactic. Both generally agree that more research is needed.
Iron-fertilization research, however, is caught in a catch-22. It's impossible to know large-scale effects without large-scale testing, but large-scale testing is limited by concerns about the effects.
The United Nations has declared a moratorium on oceanic iron-fertilization studies, and the International Maritime Organization has also limited research. But some companies and countries are pushing for restrictions to be lifted. In the case of a joint Indian-German expedition that fertilized 115 square miles of ocean in 2009, the restrictions have already been ignored.
The new report falls squarely into the middle of this fight.
"There's an absolute need for remedies involving carbon sequestration, but they have to have a scientific foundation. At this point, iron fertilization doesn't have that," said Cochlan.
Cochlan's team, led by University of Western Ontario phytoplankton specialist Charles Trick, added iron to tanks of water taken from the Gulf of Alaska, in an area where earlier researchers had conducted iron fertilization experiments.
They found that Pseudonitzschia, a common genus of algae, thrived on the iron. Pseudonitzschia at first accounted for a small fraction of algae and plankton in the water, but soon made up 80 percent of some tank populations.
Pseudonitzschia appears to benefit from its ability to produce domoic acid, which binds with iron and can then be reabsorbed by the algae. But unfortunately for other organisms, domoic acid is a potent toxin.
Cochlan, who previously studied a massive 2004 Pseudonitzschia bloom off the coasts of British Columbia and Washington, said the ecological consequences of an iron-fertilization-fed bloom could be profound, killing large numbers of animals and creating a steady injection of domoic acid into marine food chains, where it could accumulate in fish consumed by people. In humans, domoic acid produces permanent, short-term memory loss, and can even be fatal.
"Eventually, the toxicity subsides when the cells die. But doing a sustained iron enrichment experiment would mean that you'd want to keep these blooms going continuously," said Cochlan.
The researchers warned against drawing absolute conclusions from a small-scale study. But even if preliminary, the findings do suggest that researchers who've suggested that Pseudonitzschia could only bloom along coastlines, and not on the open sea, were wrong.
Later this month, scientists and policy experts will meet in Asilomar, California to discuss geoengineering risks and regulation. The meeting is organized by the Climate Response Fund, a nonprofit supporter of geoengineering research. Its director is Margaret Leinen, the former chief science officer of Climos, a San Francisco iron-fertilization company founded in 2005. Climos originally planned to sell fertilization-based carbon offsets, but after being criticized for jumping ahead of science has re-purposed itself as a research contractor.
"If domoic acid is produced by artificially stimulated ocean iron-fertilization blooms, it is likely produced during natural ones as well," Climos said in a statement March 15. "We need to understand exactly how deep-ocean phytoplankton respond to iron, be it naturally or artificially supplied, whether and in what situations domoic acid is produced, and how the ecosystem is or is not already adapted to this."
A key difference between natural and artificial iron supply is location, Cochlan said. There have not been any Pseudonitzschia blooms in the open ocean where iron fertilization is being considered.
"You're going to change the base of the food web," he said. "Going ahead with experiments like these without knowing what's up the chain is foolhardy."
Image: A 2004 Pseudonitzschia bloom off the Washington coast/NASA
See Also:
- U.N. Says 'No,' Climate Hackers Say, 'Yes We Can'
- Ocean Fertilization Works -- Unless It Doesn't
- Scientists Rank Global Cooling Hacks
- Report From Antarctica: Geoengineering the High Seas
- Geoengineering Quick-Fix Would Wreak Ozone Havoc
Citation: "Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas." By Charles G. Trick, Brian D. Bill, William P. Cochlan, Mark L. Wells, Vera L. Trainer, and LisaD. Pickell. Proceedings of the National Academy of Sciences, Vol. 107 No. 11, March 16, 2010.
Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.
