It’s been called climate change’s ‘evil twin.’ As carbon dioxide builds up in the atmosphere, it dissolves in the ocean, creating carbonic acid that is disrupting the pH balance of the ocean. Voila, ocean acidificatoin. It’s estimated that the ocean is now 30% more acidic than it was 150 years ago. That could spell trouble for animals like corals and clams that build skeletons and shells out of calcium carbonate, because acidic conditions limit the amount of calcium carbonate in the water. It’s a problem that the National Academy of Science says has received too little attention.
Scott Doney – an ocean acidification researcher at Woods Hole Oceanographic Institution – has said that New England is the most vulnerable region in the country when it comes to the impacts of ocean acidification. At a conference in early 2009, he said that ocean acidification could start affecting shellfish within 20 years.
Turns out, that timeline may be too generous. Scientists from the School of Marine and Atmospheric Sciences at Stony Brook University say two important New England shellfish – quahogs and bay scallops – are already feeling the burn. The researchers simulated future scenarios with carbon dioxide levels double (or more) current levels and saw dramatic effects – severe shell defects, higher death rates, and slower growth. Numerous other studies have documented similar impacts. What was novel about this study is the fact that the team also simulated pre-industrial acid levels and found that the shellfish developed more quickly and had survival rates that were almost double those of shellfish grown in modern water conditions. ArsTechnica’s Nobel Intent blog says that’s probably a conservative estimate of differences in survival, since the lab conditions don’t include pollution or predators.
The authors helpfully point out that they’ve eliminated predation in their lab conditions. If the animals were subject to being eaten, the weaker shells that form at higher CO2 levels would almost certainly increase the mortality.
Overall, they suggest that population crashes in bivalves have been ascribed to a number of stresses, like overfishing and pollution, but it’s possible that ocean acidification has also been at work in these cases. Given that the Earth has experienced higher CO2 levels in the past, why are they being hit so hard now? According to the paper, it’s actually been over 24 million years since levels are likely to have been this high, and many shellfish have diversified more recently than that; any changes in CO2 in the intervening time have also been far more gradual than the current pace.
Many scientists have expressed concern about the ability of marine life to keep up with the pace of changes in ocean chemistry and temperatures. News that some animals are already struggling to survive just adds urgency to those worries.
Heather Goldstone, CLIMATIDE, 22 September 2010. Article.
