Environment / Ocean

The bleak prognosis for marine species—and ultimately humans—in an environment of unchecked ocean acidification has prompted scientists to suggest a number of mitigation strategies.

1  One proposal, first suggested in the late 1980s by oceanographer John Martin of the Moss Landing Marine Laboratories in California, involves seeding ocean surfaces with iron to promote phytoplankton blooms that will soak up carbon dioxide, eventually exporting it into the deep ocean. The plan has the added theoretical benefit of reducing atmospheric carbon. The first part of the process, the phytoplankton bloom, has already been demonstrated in small-scale tests in the South Pacific and the equatorial Pacific Ocean. But no one has ever shown that a carbon drawdown will persist over time, making many scientists fear that the effort could send the ocean’s biochemical systems careering in unforeseen directions.

2  A second tactic under consideration at places like the Carnegie Institution of Washington and the University of California at Santa Cruz is to neutralize the seas—possibly with limestone from, say, the White Cliffs of Dover. But there are problems here as well: The scale of the mining and transportation effort to harvest these minerals would be enormous and extremely expensive. Moreover, it would itself involve the expenditure of large amounts of energy and thus the emission of additional carbon dioxide into the atmosphere.

3  Last year a team of scientists led by Kurt Zenz House, a doctoral candidate at Harvard University, proposed something they call engineered weathering, inspired by a natural process in which slightly acidic freshwater is neutralized by exposure to alkalizing minerals. Under House’s proposal, hydrochloric acid would be harvested from the ocean by a specialized electrochemical treatment and then exposed to silicates, resulting in a net alkalizing shift.

When it comes to saving the seas, of course, the kind of technological fixes suggested here would be measures of last resort. Bärbel Hönisch, a marine biologist and geochemist at Columbia University’s Lamont-Doherty Earth Observatory, points out that “none of these strategies has been tested over the long term, and the potential effects on the ecosystem are uncertain.” In the end, she adds, the best solution might be the most obvious one: Dramatically reduce our carbon emissions.

Carl Brenner