Oceans

Ocean acidification and the worst mass extinction in geologic history

Most of us know that sixty-five million years ago (mya) the dinosaurs, along with an estimated seventy-five percent of all species on earth, became extinct. Lesser known, is the even more catastrophic event that took place 252 mya when as much as 96% of all marine species and over 70% of all terrestrial species disappeared forever. Scientists refer to this event as the “Permo-Triassic Boundary” (PTB) mass extinction because it occurred 252 mya at the boundary of the Permian and Triassic periods.

Even more unsettling than the fact that these extinction events occur at all, is that paleoclimatologists are unearthing new evidence to suggest that the coupled effect of climate change and ocean acidification is a very likely cause for the PTB mass extinction. Humanity as an urgent need to evaluate the connection between climate change, ocean acidification, and potential similar catastrophic events in the future.

Scientists have long debated exactly what caused the PTB mass extinction, but new evidence published in Science this past April indicates that ocean acidification played a major role. Paleoclimatologist, Mathew Clarkson and his colleagues, analyzed different forms of Boron, called Boron “isotopes”, to recreate how the pH of the ocean changed during the extinction. They discovered that an isotope of Boron associated with more acidic seawater became more abundant during the worst pulse of the extinction. Thus, they were able to infer that the ocean became much more acidic during the PTB mass extinction period.

Ocean acidification has been called “climate change’s evil twin” because the two phenomena are inextricably linked. When atmospheric CO­­ is dissolved in the ocean it causes the water to become more acidic, eventually making life impossible for a wide variety of organisms. However, the ocean, like our blood, is a naturally buffered solution, and it can resist changes in pH up until a certain point. Clarkson and his team used carbon isotope data and climate models to hypothesize what may have overwhelmed the ocean’s natural buffering capacity and acidified the oceans during the PTB mass extinction. They concluded that the most likely cause was a massive injection of carbon into the atmosphere from volcanic eruptions in Siberia believed to occur during that timeframe. Clarkson’s team estimates that these eruptions were responsible for releasing 2.4 trillion kilograms of carbon per year for 10,000 years. The resulting changes in the atmosphere and oceans were devastating.

Clarkson’s report shows that the worst extinction in geologic history coincides with a major ocean acidification event that was most likely triggered by a rapid injection of carbon into the atmosphere. It reminds us that the ocean is a buffered solution that can protect itself up until a certain point. If conditions such as rising levels of atmospheric carbon overwhelm the buffering capacity of the ocean, it can result in major changes in the pH of the ocean, and thus catastrophic events for life on Earth.

Featured Image by Toby Hudson via Wikipedia

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Categories: Oceans

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