Perils of Ocean Acidification
By Dr Arvind kUmar
The findings of a recemtly published research, undertaken by a group of researchers from the United States and four other countries, reinforce warnings from many climate scientists that the world’s oceans, a vital source of fish food protein, may be turning acidic faster today from human CO₂ emissions than they did during four major episodes of animal and plant extinctions in the last 300 million years, when natural surges of CO₂, probably from catastrophic volcanic eruptions or meteor strikes, sent global temperatures soaring. The researchers reviewed existing evidence on the impact of changes in the atmospheric concentration of carbon dioxide (CO₂), the main global warming gas, from decades of research on fossilized remains and other evidence from Earth’s geologic record. The scientific findings suggest that acidification is now happening at least 10 times more quickly than during PETM, raising “the possibility that we are entering an unknown territory of marine ecosystem change.”
Increasingly acidic oceans and seas harm a range of marine life, from reef and shell-building organisms to the tiny snails favoured by salmon. Barbel Honisch, a paleoceanographer at Columbia University’s Lamont-Doherty Earth Observatory, who was a lead author of the recent review of the scientific evidence, says: “We know that life during past ocean acidification events was not wiped out (and that) new species evolved to replace those that died off, but if industrial carbon emissions continue at the current pace, we may lose organisms we care about — coral reefs, oysters, salmon.” Of the vast amounts of CO₂ released into the atmosphere, about one quarter of the excess CO₂ is absorbed by land plants and another quarter by the oceans. The excess CO₂ from the atmosphere reacts with seawater to form carbonic acid. Over time, this mild acid is neutralized by fossilized carbonate shells on the sea floor. But if CO₂ goes into the oceans too quickly, as it is now, it can deplete the carbonate ions that corals, mollusks and some plankton in the seafood chain need for reef and shell-building.
