Ocean Acid Levels Rose 252 Million Years Ago to Cause Biggest Mass Extinction

A new study has found that the largest extinction of ocean life was due to acidification, fate that could repeat given the current level of greenhouse gas emissions.

According to Nature, the 'Great Dying' happened at the end of Permian period about 252 million years ago. The extinction event, which wiped out over 90 percent of the marine life and nearly two-thirds of land animals, happened over a 60,000-year period. Researchers warned that the Great Dying could possibly be the worst case scenario of rate of carbon emissions in the modern day, which has caused detectable acidification of oceans.

"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. 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," said Matthew Clarkson, School of Geosciences at University of Edinburgh.

The team arrived at its findings after examining boron in rocks. Two isotopes of boron are found in oceans. Acidity affects relative amounts of the isotopes. Scientists used boron isotope levels as markers to understand water pH dropped by 0.7 units over 10,000 years. In comparison, ocean levels have dropped by 0.1 pH units due to fossil fuel emissions.

Boron analysis also showed that the extinction happened in two phases and it was during the second phase that the pH levels dropped significantly, which scientists have attributed to massive volcanic eruptions in Siberia.