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Ocean Acidification Triggered Greatest Mass Extinction Ever

Apr 10, 2015 03:25 PM EDT

It's no secret that ocean acidification caused by climate change is currently wreaking havoc on our oceans, but a new study shows that acidic oceans also triggered the greatest mass extinction ever on Earth.

Thanks to extreme volcanic activity about 252 million years ago, the world's oceans changed so drastically that it wiped out more than 90 percent of marine species, and more than two-thirds of the animals living on land.

The event occurred when Earth's oceans absorbed huge amounts of carbon dioxide (CO2) from volcanic eruptions, which thus changed the chemical composition of the oceans - making them more acidic.

While global ecosystems were already unstable - with increased temperatures and widespread loss of oxygen in the oceans - it was highly acidic oceans that pushed both marine and land-based species over the edge, researchers say. This resulted in what is known as the Permian-Triassic Boundary extinction, which took place over a 60,000-year period. Acidification of the oceans lasted for around 10,000 years.

The findings, published in the journal Science, are helping scientists better understand the threat that modern marine life face today in the midst of climate change, which is driving harmful ocean acidification.

It's true that during the greatest extinction of all time, the amount of carbon added to the atmosphere was probably greater than today's fossil fuel reserves, note the University of Edinburgh researchers.

However, the carbon was released at a rate similar to modern emissions, and this fast rate of release was a critical factor driving ocean acidification.

Oceans can absorb some CO2 but the large volume released - at such a fast rate - changed the chemistry of the oceans, according to the study. What's more, the mass extinction of both marine and land-based animals demonstrates that extreme change took place in all of Earth's ecosystems. (Scroll to read on...)

To find out more about this ancient mass extinction, the research team analyzed rocks unearthed in the United Arab Emirates (UAE) - which were on the ocean floor at the time and contain a detailed record of changing oceanic conditions during the event. Then, they used this data to develop a climate model.

What they found, for the first time, is that highly acidic oceans were to blame for the Permian-Triassic Boundary extinction.

"Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now," Dr. Matthew Clarkson, who coordinated the study, said in a statement. "This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions."

Ocean acidification today is already causing all sorts of damage to marine life, robbing sharks of their predatory senses, making calcifiers struggle to survive, and diminishing corals in the Great Barrier Reef.

In fact, the Great Barrier Reef's growth rate has plummeted 40 percent since the mid-1970s, and scientists worry that this iconic ecosystem, a World Heritage Site, may completely collapse under climate change.

And ocean acidification doesn't just pose a threat to marine life, but to US coastal communities that depend on these species as well. So while that 2 degrees climate goal that we've been reaching for is supposed to prevent catastrophic consequences for life on Earth, some have deemed it "utterly inadequate."

Where does that leave us? The bottom line is, if we want to prevent another mass extinction event from occurring, we have to act fast.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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