What many people do not realize is that nearly a third of carbon dioxide emitted by humans is dissolved in the oceans. Some of that forms carbonic acid, which makes the ocean more corrosive.
In a troubling new discovery, scientists studying ocean waters off California, Oregon and Washington have found the first evidence that increasing acidity in the ocean is dissolving the shells of a key species of tiny sea creature at the base of the food chain. The animals, a type of free-floating marine snail known as pteropods, are an important food source for salmon, herring, mackerel and other fish in the Pacific Ocean. Those fish are eaten not only by millions of people every year, but also by a wide variety of other sea creatures, from whales to dolphins to sea lions.
If the trend continues, climate change scientists say, it will imperil the entire ocean environment.
“These are alarm bells,” said Nina Bednarsek, a scientist with the National Oceanic and Atmospheric Administration in Seattle who helped lead the research. “This study makes us understand that we have made an impact on the ocean environment to the extent where we can actually see the shells dissolving right now.”
Scientists from NOAA and Oregon State University found that in waters near the West Coast shoreline, 53 percent of the tiny floating snails had shells that were severely dissolving—double the estimate from 200 years ago. Until now, the impact on marine species from increasing ocean acidity because of climate change has been something that was tested in tanks in labs, but which was not considered an immediate concern such as forest fires and droughts.
The new study, published in the Proceedings of the Royal Society B, a scientific journal based in England, changes that. “The pteropods are like the canary in the coal mine. If this is affecting them, it is affecting everything in the ocean at some level,” said one of the nation’s top marine biologists, Steve Palumbi, director of Stanford University’s Hopkins Marine Station in Pacific Grove.
The vast majority of the world’s scientists—including those at NOAA, NASA, the National Academy of Sciences and the World Meteorological Organization—say the Earth’s temperature is rising because of humans burning fossil fuels like oil and coal.
But what many people do not realize is that nearly a third of carbon dioxide emitted by humans is dissolved in the oceans. Some of that forms carbonic acid, which makes the ocean more corrosive.
Over the past 200 years, the ocean’s acidity has risen by roughly 30 percent. At the present rate, it is on track to rise by 70 percent by 2050 from preindustrial levels. More acidic water can harm oysters, clams, corals and other species that have calcium carbonate shells. Generally speaking, increasing the acidity by 50 percent from current levels is enough to kill some marine species, tests in labs have shown.
If people reduce emissions of fossil fuels, cutting carbon dioxide levels in the decades ahead, the damage to the oceans can still be limited. “But if we keep on the emissions profile we have now, by 2100 the oceans will be so harmed it’s hard to imagine them coming back from that in anything less than thousands of years,” Palumbi said.
“We are in a century of choice,” he said. “We can choose the way we want it to go.”
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