Ocean Iron Fertilization Could Stimulate Toxic Algae Blooms in Open Ocean

bubbles in water photo

photo: Sherrie Thai/Creative Commons

There's no doubt that geoengineering brings out passionate emotions both pro and con, as recent debate on TreeHugger about the sort of-moratorium on some research coming out of the Convention on Biological Diversity amply illustrates. Backing up the caution side (which I admit I'm firmly a part of) is a new piece of research coming from UC Santa Cruz, and published in Proceedings of the National Academy of Sciences, which shows that a toxin-producing algae normally thought limited to coastal waters (and perhaps partial inspiration for The Birds) can be stimulated to grow rapidly in the open ocean when iron from natural or artificial sources is present. Science Codex sums up the nut of it:

Blooms of diatoms in the genus Pseudo-nitschia, which produce a neurotoxin called domoic acid, are a regular occurrence in coastal waters. During large blooms, the algal toxin enters the food chain, forcing the closure of some fisheries (such as shellfish and sardines) and poisoning marine mammals and birds that feed on contaminated fish. But until now, blooms of these algae in the open ocean have attracted little attention from researchers.

Study lead author, Mary Silver says that normally pseudo-nitschia don't have much effect, but "these species are incredibly responsive to iron, often becoming dominant in algal blooms that result from iron fertilization. Any iron input might cause a bloom of the cells that make the toxin." Silver adds that natural deposits of iron in the open ocean (from volcanic eruptions, dust storms, etc) have occurred for millions of years, but are sporadic occurrences.

"To do iron enrichment on a large scale could be dangerous," Silver notes, "because, if it causes blooms of pseudo-nitschia, the toxin will get into the food chain, as it does in the coastal zone."

Old Samples From Iron Fertilization Experiments Showed Toxins
How did Silver and colleagues reach this conclusion (and warning)? By examining pseudo-nitschia cells found in samples collected from the Gulf of Alaska in 2007, which ended up showing the presence of domoic acid. This prompted a reexamination of old samples from ocean iron fertilization experiments from 1995 and 2002--which, despite the age of the samples and the assumption that is would have broken down, still contained the toxin.

Kenneth Coale, report co-author and director of Moss Landing Marine Laboratories, says that these results mean, "we should redouble our efforts to reduce carbon emissions," as this work "definitely reveals a wrinkle in plans [to use ocean iron fertilization to reduce atmospheric carbon dioxide levels]."

Breaking an Ecosystem Easier Than Fixing One
Obviously the efficacy of any particular geoengineering method can't be determined by one study--and there a examples both proving both its worth or lack thereof, as well as ones like this showing potential unintended consequences--and more research would be needed to determine that. But since, as Coale aptly puts it, "It is much easier to break an ecosystem than it is to fix one," the scale at which such research is conducted, so as to minimize potential side effects to the wider ecosystem, is not a trivial concern.

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More on Geoengineering:
Geoengineering Unable to Fully Stop 21st Century Sea Level Rise: Report
Royal Society Says Geoengineering Humanity's Last Hope - But Emissions Reductions Must Be Top Priority
UN, Biodiversity Experts Want to Ban Geoengineering Research
Why the UN Moratorium on Geoengineering Is a Good Thing, Maybe
More on Ocean Iron Fertilization:
Iron Fertilization Experiment Proves Geo-engineering Unpredictable
15-20 Times Less Carbon Sequestered by Ocean Iron Fertilization Than Some Estimates Claim: New Report
Volcano-Stimulated Rebound of 2010 Salmon Run Challenges Anti-Science Environmentalism

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