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Strategies to lock CO2 in oceans could have toxic results

March 15, 2010 -- Fertilizing regions of the world's oceans with iron, a strategy designed to lock away excess carbon dioxide and curb climate change, could poison ocean waters with a neurotoxin harmful to marine life and human health, according to a new study. William Cochlan, a senior research scientist at SF State's Romberg Tiburon Center for Environmental Studies, was part of the team that published the findings today in the journal Proceedings of the National Academy of Sciences.

A photograph of Senior Research Scientist William Cochlan and four colleagues on board the research vessel Thomas G. Thompson  on the rough seas of the subarctic northeast Pacific Ocean. They are conducting iron enrichment experiments and the image shows them with large bottles containing ocean water samples.

Senior Research Scientist William Cochlan (second from right) and colleagues conduct iron-enrichment experiments using deckboard incubators aboard the research vessel Thomas G. Thompson in the subarctic northeast Pacific Ocean. Credit: William Cochlan

Adding minute quantities of iron to ocean waters is believed to trigger the growth of microscopic algal blooms, which consume vast amounts of carbon dioxide, removing it from the atmosphere and storing it in the deep sea for centuries. During the past two decades, debate on such geo-engineering strategies has largely focused on their effectiveness as a means to store carbon dioxide and slow global warming, rather than the ecological impact on marine life and birds. Very little research has examined exactly what kind of microalgae will bloom after fertilization and whether they will be toxic or harmless.

Cochlan and his colleagues report that iron enrichment would likely favor the growth of Pseudo-nitzchia, a group of phytoplankton species that produce a potent neurotoxin that causes the human illness Amnesic Shellfish Poisoning. The naturally occurring biotoxin, called domoic acid, could put human health at risk if accumulated in shellfish, and can damage marine mammals and seabirds that feed on small fish that feed on plankton. In coastal systems, such toxic blooms contaminate organisms such as shellfish and could cause economic losses through the closure of commercial fisheries.

"Such large-scale manipulations of the marine environment have provided a wealth of scientific information and have greatly increased our understanding of the important linkages between atmospheric and oceanic systems," Cochlan said. "But as far as an effective mechanism to mitigate climatic change -- we as oceanographers cannot support such large-scale commercial efforts since we have virtually no knowledge of how they will impact natural marine ecosystems in the long-term."

Based on ship-based experiments conducted in the subarctic Pacific Ocean near the Gulf of Alaska, the researchers found that iron enrichment increased the concentration of the toxin produced by each Pseudo-nitzchia single-celled organism. The scientists also found that in water samples enriched with iron, the population of the toxic algae Pseudo-nitzchia doubled in nine days relative to control samples, suggesting that the addition of iron creates conditions that give the toxic species an advantage over non-toxic species, increasing the chances of an ecologically harmful outcome.

In addition to Cochlan's participation, Brian Bill, SF State graduate student in marine biology, conducted his dissertation research on these toxic phytoplankton samples and performed sensitive biotoxin measurements while at sea. His work was funded by the National Marine Fisheries Service Advanced Studies program. Bill plans to graduate this year and is already employed by the National Oceanic and Atmospheric Administration NOAA) at the Northwest Fisheries Science Center in Seattle.

"Iron enrichment stimulates toxic diatom production in High Nitrate Low Chlorophyll areas" was published today in the Online Early Edition of the Proceedings of the National Academy of Sciences. The study was funded by the National Science Foundation, the U.S. Department of Energy and the NOAA.

The research was led by Charles Trick of University of Western Ontario in collaboration with SF State researchers William P. Cochlan and Brian D. Bill, as well as Mark L. Wells and Lisa D. Pickell of the University of Maine and Vera L. Trainer of NOAA's Northwest Fisheries Science Center.

-- Elaine Bible


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