What's the harm in boosting phytoplankton growth? Potentially plenty, say scientists. Enhancing the process with ammonia, as Ocean Technology Group proposes, could induce toxic algal blooms, actually decrease the CO2 uptake efficiency and produce nitrous oxide, an ozone-layer-attacking greenhouse gas, say Chisolm of MIT and others. The notion of adding iron to the oceans also gets mixed, though not all negative, science reviews.
Computer models show ocean fertilization, even practiced on a huge scale over an extended period of time, would not be enough to mitigate climate change," says Chisholm. Further, "Large-scale ocean manipulation will change the basic biogeochemical cycles, which in turn will result in other changes." These alterations may be end up being worse than the initial problem. Greater phytoplankton growth from fertilization in one area of the world's oceans, for instance, could mean, due to ocean currents, dangerous oxygen depletion in fishing grounds many thousands of miles from the fertilization site. Related atmospheric-circulation patterns could be affected, with unpredictable results.
Yet Another Idea
Ken Caldeira at Lawrence Livermore National Laboratory points out that high atmospheric CO2 acidifies the ocean, as does ocean fertilization. To avoid that, he and colleagues Kevin Knauss and Greg Rau propose an alternative. They suggest reacting carbon dioxide with crushed limestone and seawater, and then releasing that into the ocean. "But all options share the issues of having an effect on marine ecosystems," Caldeira cautions.
There are many unknowns, but one thing is clear: more research is needed to develop sound solutions--and soon. The recent monsoon-like rains and floods in Europe have raised awareness, if not alarm, about the necessity of undoing climate changes that human activities have wrought, points out Victor Smetacek of the Alfred-Wegener Institute for Marine and Polar Research in Germany. "It¿s clear that we do not have a choice in the matter," he adds.
Vivien Marx divides her time between Cambridge, Mass., and Cologne, Germany.