Sea Butterflies Defend Their Homes Against an Acidic Ocean

We all know that carbon dioxide (CO2) is produced from burning fossil fuels, and that it contributes to global warming. But have you heard about the “evil twin” of global warming, also caused by CO2–ocean acidification? The ocean absorbs about 30% of the CO2 that humans emit each year. As CO2 dissolves into the ocean, it forms carbonic acid, effectively making the ocean acidic. Animals that use a substance called calcium carbonate to build their shells and skeletons are vulnerable to acidic conditions, as their hard parts may dissolve. Microscopic swimming snails called pteropods or sea butterflies are common in the Southern Ocean. With incredibly delicate shells thinner than a human hair, pteropods are often considered to be the organisms most vulnerable to ocean acidification. Using microscopes and X-rays, we took extremely detailed images of these tiny shells and found that pteropods have a couple of clever tactics to defend their “homes” against ocean acidification.

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