October 9, 2013 — Like other aspects of climate science, ocean acidification (OA) science has drawn the fire of skeptics. Some have used the findings of OA researchers to argue either that the science isn’t settled or that OA isn’t necessarily such a bad thing
By way of background, sufficiently acidic seawater can either prevent organisms from forming their protective shells, or actually dissolve shells once they’re formed. Creatures that build their shells from calcium carbonate are the most vulnerable. But variations in shell structure—such as a matrix of carbonate and organic material, or an organic outer layer—seem to reduce the impact. With all that variability in the response of marine organisms, it isn’t hard to cherry-pick the data.
In particular, climate change deniers cite a study by Justin Ries of the University of North Carolina at Chapel Hill. Ries measured changes in shell calcification in a number of species, including mollusks (clams, oysters, scallops), echinoderms (sea urchins), and crustaceans (crabs, lobsters, shrimp). Although calcification declined in most of his test subjects, in the crustaceans it actually increased, and was greatest at the highest carbon dioxide concentration tested, 2856 parts per million—well beyond current ocean levels of about 400 ppm, and way beyond anything in even the direst forecasts. (The higher the CO2 concentration, the lower the pH and the greater the acidity.)
Researchers at the Monterey Bay Aquarium Research Institute (MBARI) have been studying the impacts of increased CO2 in the deep marine environment for over a decade. This “benthic respirometer” on the floor of Monterey Canyon has chambers in which a variety of deep sea organisms are exposed to differing levels of CO2 to see how they respond.
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