The end of the ‘silent sea’

Man-made sounds and increasingly acidic oceans are driving whales and dolphins to distraction – sometimes fatally. Eric Reguly reports

December 13, 2008

ROME — Whale and dolphin strandings are almost always a mystery. As soon as the animals wash, or propel themselves, ashore, the blame game starts.

Were their navigational skills thrown off-kilter by chemical pollution? Were they in pursuit of food and made a fatal turn? Were they chased into the shallows by fishing boats? Did something scare them?

A new theory says man-made carbon dioxide emissions could be at fault.

Scientists have known for some time that carbon dioxide, the most common greenhouse gas, is making the oceans ever more acidic. They have also known that acidic seawater absorbs sound less readily, that is, it transmits sound farther. What they did not know until recently is that even fairly small changes in acidity levels can have a dramatic effect on seawater’s noise-transmission capability.

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