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By Root 827 0

than warmer oceans, another acidification hot spot occurs in the Arctic, where melting sea ice in addition leaves more of the sea surface in contact with the atmosphere and therefore able to absorb carbon dioxide today than previously. In the summer of 2008 researchers on board the Canadian Coast Guard’s heavy icebreaker the Louis S. St-Laurent found rapidly acidifying waters in the Canada Basin, an area of frigid seas north of the Canadian and Alaskan coasts. By measuring the salinity and chemical properties of the seawater they sampled, the scientists were able to conclude that this rising acidity was “a direct consequence of the recent extensive melting of sea ice” in the area.9 This suggests that the climate change and ocean acidification boundaries are linked not only in their cause but also in their effects.

LIFE IN THE ACID BATH

Marine biologists are today some of the most worried people on the planet. Coral reefs, probably the world’s most important oceanic habitat, are already in decline almost everywhere because of global warming, overfishing, and other human impacts. But ocean acidification, unless rapidly addressed, will kill them completely. Reefs are entirely made of calcium carbonate, and that makes them extremely vulnerable to more acidic oceans. Past a certain tipping point, reefs will not just die—they will begin to physically dissolve in the corrosive water around them, and eventually disappear completely.

Already today there is evidence that acidification is beginning to have an effect on corals, even in protected areas like Australia’s Great Barrier Reef. In January 2009 Australian marine biologists reported a 14 percent decline in calcification rates measured over 69 different locations up and down the Barrier Reef over the 15 years between 1990 and 2005. Because corals, like trees, lay down growth rings, the scientists were also able to note that these changes were unprecedented within at least 400 years—ruling out natural oceanic fluctuations and other recurring cycles.10 Similar multiyear declines in coral growth have also been observed in the Caribbean Sea11 and the Andaman Sea off Thailand,12 likely also attributable to acidification, higher temperatures, or both. Once again, the interaction between the climate and acidification boundaries is evident: Laboratory studies with corals in tanks have shown that while hotter and more acidic waters are both bad for reefs, the combination of the two is particularly deadly.13

A natural laboratory for the impact of rising oceanic acidity can be found off Italy’s western Mediterranean coast, where volcanic CO2 bubbles out of vents in the sea floor. Scientists scuba diving around these vents have noted that calcareous corals are unable to survive in the area, while other animals with chalky skeletons—like sea snails—show damage to their shells.14 In the eastern tropical Pacific, scientists have found that coral reefs in naturally more acidic seas are degraded and unstable.15 The outlook is grim: Even though some specific coral species seem to be resilient to acidification,16 tropical reefs globally may start dissolving as early as mid-century if atmospheric carbon dioxide concentrations are allowed to double by that time from their preindustrial level.17

The entire marine ecosystem is at risk from acidification, from the tropics to the poles. In the Arctic, bottom-dwelling organisms like mussels and clams—vital food for diving seabirds, bearded seals, gray whales, and walrus—may already be suffering the impacts of rising acidity.18 The acidification hot spot on the western U.S. continental shelf could put at risk the giant kelp forests that are important centers of marine biodiversity, and affect lobsters, sea urchins, snails, mussels, and hundreds of other ocean-dwelling animals and plants.19 This and other upwelling zones that are experiencing the earliest effects of ocean acidification also tend to support flourishing fisheries—from the Peru Current to Alaska’s billion-dollar pollock fishery. Once again, the planetary boundaries interact in a worrying