Fossils Reveal How Ocean Acidification Can Cause Mass Extinction

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66 million years ago life on Earth was devastated by a cataclysmic mass-extinction event after an asteroid some 6 miles wide smashed into the planet’s surface. The impact of the rogue planetoid wiped out about 75 percent of global species, including the dinosaurs.

Now, researchers as part of a Yale-led study are hypothesizing that this event may have also caused a devastating rise of acidity levels in the ocean which is a problem we also face today.

Known as the K-T extinction, the event marks the end of the Cretaceous Period and start of the Tertiary Period. As well as starting a catastrophic chain of events that included tsunamis and earthquakes, the asteroid expelled a massive amount of sulphur-rich bedrock into the atmosphere which could have caused violent acid rains.

This would have directly led to the acidification of the planet’s seas. “Before the impact event, we could not detect any increasing acidification of the oceans,” said the study's lead author, Michael Henehan, a scientist at GFZ German Research Centre for Geosciences in Potsdam, Germany.

According to the paper, published in the Proceedings of the National Academy of Sciences, the after-effects of the impact radically altered the chemical make-up of the ocean which in turn made the acidic seas uninhabitable to the tiny creatures such as plankton. These diverse organisms provide a crucial source of food to many other aquatic organisms and species, thus, the severe disruption to the marine food chain caused by K-T asteroid may have played a significant part in the scale of the mass extinction.

While the sudden intensification of the ocean’s acid levels would have lasted less than 1000 years – less than a heartbeat of geological time – this would have been, “long enough to kill off entire ecosystems,” says Pincelli Hull, co-author of the paper and professor of geology at Yale. While this may all make for stimulating reading for some, it comes with an ominous warning for many as today’s oceans are also undergoing a process of acidification.

There may still be some way to go for current acidification levels to reach the same magnitudes as the K-T extinction, but it is, “moving toward that scale, but it’s not quite there yet,” says Hull. However, the combination of ocean acidification, extreme climate events, and environmental disaster could accelerate the chances of a major ecological collapse on the planetary scale.

You should think of [ocean acidification] as the straw that broke the camel’s back. It’s dark, it’s really cold after the impact — and the ocean has acidified.

Pincelli Hull

To reach their hypothesis the research team examined a plethora of tiny plankton fossils, known as foraminifera, found in clay samples taken from an underground cave in the Netherlands – the tiny fossils measure between 150 and 212 microns. Analyzing the chemical composition of the samples, dated before and after the K-T event, produced an enormous amount of data regarding the changing conditions in the marine ecosystem. “It was a herculean effort to get these measurements,” Hull said.

One impact of the study is that it offers researchers the ability to understand the Earth’s atmosphere before, during and immediately after the K-T extinction. Moreover, it may serve as an early-warning system for us today as current acidity levels in the oceans are climbing.

Acidification in the seas today is the result of rising carbon emissions. Around 25 percent of CO2 released by the burning of fossil fuels dissolves into the ocean. This data, released by the NOAA Ocean Acidification Program, outlines the harmful consequences of excess carbon dioxide in the atmosphere and refers to ocean acidification as “climate change’s evil twin.”

So, even though the K-T extinction and death of the dinosaurs may seem mythological in relation to today’s planetary events, the role ocean acidification played in this apocalyptic episode should not be ignored.

One UN report states that the climate crisis has warmed the Earth’s oceans, making them more acidic and led to mass die-offs in some species and could lead to the extinction of many more.

David J. Cross, M.A

Written by

David J. Cross, M.A

David is an academic researcher and interdisciplinary artist. David's current research explores how science and technology, particularly the internet and artificial intelligence, can be put into practice to influence a new shift towards utopianism and the reemergent theory of the commons.

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