Acidic oceans killed 90% marine species, over 67% terrestrial animals 252m years ago

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A new study, co-ordinated by the University of Edinburgh, has found that acidic oceans triggered greatest extinction of all time 252 million-years-ago which saw annihilation of 90 per cent of marine species and more than two-thirds of the terrestrial animals at the time.

Researchers have said that this acidification of oceans was a direct result of absorption of huge amounts of carbon dioxide from volcanic eruptions. This changed the chemical composition of the oceans, making them more acidic, with catastrophic consequences for life on Earth.

The findings of the latest study, published in the journal Science, are helping scientists understand the threat posed to marine life by modern-day ocean acidification. The amount of carbon added to the atmosphere that triggered the mass extinction was probably greater than today’s fossil fuel reserves.

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

The Permian-Triassic Boundary extinction took place over a 60,000 year period, researchers said. Acidification of the oceans lasted for around 10,000 years.

Ocean acidification was the driving force behind the deadliest phase of the extinction, which dealt a final blow to an already unstable ecosystem. Increased temperatures and widespread loss of oxygen in the oceans had already put the environment under pressure.

Previous Studies

Previous studies have provided similar conclusion for the mass extinction and one of them from MIT published back in 2013 said that rain as acidic as undiluted lemon juice may have played a part in killing off plants and organisms around the world during the most severe mass extinction in Earth’s history.

In the MIT study, researchers created global climate models of scenarios in which repeated bursts of volcanism spew gases, including sulfur, into the atmosphere. From their simulations, they found that sulfur emissions were significant enough to create widespread acid rain throughout the Northern Hemisphere, with pH levels reaching 2 — as acidic as undiluted lemon juice. They say such acidity may have been sufficient to disfigure plants and stunt their growth, contributing to their ultimate extinction.


Increased amounts of carbon dioxide in atmosphere and oceans have always been pegged as a warning sign for climate change and global warming and the latest research just strengthens the already established fact that increased CO2 concentrations have a negative impact on life on Earth.

A study in 2013 by U.S. Geological Survey established that acidification of the Arctic Ocean is occurring faster than projected and this could have important consequences for health of the Arctic ecosystem.

Ocean acidification is the process by which pH levels of seawater decrease due to greater amounts of carbon dioxide being absorbed by the oceans from the atmosphere. Currently oceans absorb about one-fourth of the greenhouse gas. Lower pH levels make water more acidic and lab studies have shown that more acidic water decrease calcification rates in many calcifying organisms, reducing their ability to build shells or skeletons. These changes, in species ranging from corals to shrimp, have the potential to impact species up and down the food web.