Image: Marina Montresor, SZN / AWI
The theory is simple: throwing some iron into the ocean causes phytoplankton growth to boom, then phytoplankton die, taking large quantities of CO2 to the bottom of the seabed. But that is not what happened in a recent highly controversial iron fertilization test conducted by the research ship Polarstern. According to the Alfred Wegener Institute press release, the iron fertilization experiment "has dampened hopes on the potential of the Southern Ocean to sequester significant amounts of carbon dioxide (CO2) and thus mitigate global warming." What happened? And is this the end of the road for iron fertilization, or is it one more set of data to plug into models for successful CO2 control?
Image: NASA (http://oceancolor.gsfc.nasa.gov) / AWI
Description of the image from AWI press release: "Satellite image of sea-surface chlorophyll concentrations with our bloom encircled. Note much larger natural bloom on the upper right and the generally higher values in the southeast than elsewhere."
The experiment started out following scientists' predictions. After the addition of the iron source to the swirling current, phytoplankton biomass doubled, as can be seen by the orange-reddish swirl in the NASA image above. But the growth was mainly a soft and tasty algae called Phaeocystis. Other little creatures, known as copepods, moved in quickly to gobble up the algae, soon followed by shrimp-like amphipods which lunched on the copepods. Ultimately, these amphipods end up in the bellies of squid and fin whales, so maybe iron fertilization could be a geo-engineering solution for supporting these top-of-the-food-chain species. But certainly, the experiment did not result in tons of CO2 safely sequestered on the ocean floor, proving the iron fertilization hypothesis not yet ripe for geo-engineering scale games with mother nature.
It turns out that iron is not the only limiting factor in phytoplankton blooms in the Southern Ocean. A natural deficiency in silica led to algae blooms dominated by the shell-free Phaeocystis. It is thought that the low silica concentrations are an effect of earlier algal blooms, fertilized by iron naturally entering the Southern Ocean (which inspired the location of these experiments).
Image: G. Mazzochi, SZN / AWI
Description of the image from AWI press release: "The smaller copepod species Clausocalanus laticeps with orange bands round its midriff."
So were the experiments a failure? Well, if there is one thing a scientist knows, it is that learning what is not true can be just as instrumental to a breakthrough as an experiment which fully supports the hypothesis tested. In this case, the data collected by Polarstern will fascinate researchers for years. For example,
- The results suggest that algae are much more instrumental in nutrient recycling than previously thought.
- Data collected on gases emitted during the algal bloom will help scientists understand whether CO2 captured by algae balances out the emissions of other gases which may be stronger contributors to global warming or cause other adverse environmental impacts.
- The complex effects of nutrient balances on phytoplankton growth can be better understood.
- Research techniques in high winds and heavy seas are futher developed.
Certainly, the results give cause for futher concern about our inability to control the natural law of unintended consequences. Hopefully this will serve to discourage desperate or heroic attempts at geo-engineering. But Polarstern never set out to fix global warming. They set out to learn more about the natural world around us. And in this the expedition can claim success. Interested scientists will look forward to pubication of the results of the expedition and further studies in scientific journals and workshops toward the end of 2009.
More on Polarstern and Iron Fertilization
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German Government Green Lights Ocean Iron Fertilization Test After Review
Anti-Science Environmentalism: Iron Seeding Experiment Protested...Again