Study Finds That Geoengineering Technique of Ocean Iron Fertilization Can Stimulate Toxic Diatom Blooms
In a new collaborative study published in the Proceedings of the National Academy of Science (PNAS), oceanographers and students from Canada and the United States have demonstrated that ocean iron enrichment—a proposed geo-engineering technique designed to remove carbon dioxide from the atmosphere and curb climate change—sharply increases the chances of developing toxic diatom blooms.
Adding iron to large regions of iron-deficient but otherwise nutrient-rich, ocean waters stimulates massive blooms of phytoplankton (photosynthetic, microscopic plant-like organisms), thereby increasing carbon dioxide uptake and removal from surface waters as these cells die and sink, or are eaten by zooplankton and then sink as fecal pellets, and sequestering the excess carbon flux into the deep sea for many years to come.
The phytoplankton species of concern belong to the pennate diatom genus Pseudo-nitzschia, a group of 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.
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.
It is an indication that we are not the masters of nature when it comes to large-scale ecological manipulations. Any positive carbon sequestration must be balanced against the evident and unforeseen environmental consequences.
—Charles Trick, University of Western Ontario
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.
The research was funded primarily by the National Science Foundation (Chemical Oceanography), the US Department of Energy (Ocean Carbon Sequestration), and the US National Oceanic and Atmospheric Administration.
Charles G. Tricka, Brian D. Bill, William P. Cochlan, Mark L. Wells, Vera L. Trainer, and Lisa D. Pickell (2010) Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas. PNAS doi: 10.1073/pnas.0910579107