Special conditions of the Gulf of Mexico softened the mass extinction of marine fauna at the end of the Paleocene

(ORDO NEWS) — Fifty-five million years ago, as a result of a powerful, albeit short-term global warming, the oceans became more acidic than today, which led to the mass extinction of marine animals. However, in the Gulf of Mexico, things were much better, and the reason for this was the unique geology of this place.

Fifty-five million years ago, on the border of the Paleocene and Eocene, life on planet Earth, still recovering from the effects of the previous mass extinction, suffered another nuisance – the Paleocene-Eocene thermal maximum.

Volcanic activity led to a sharp (over the course of only 50 thousand years) release of 12 trillion tons of carbon into the ocean and atmosphere, as a result of which the temperature on the planet immediately increased by five to ten degrees Celsius.

Special conditions of the Gulf of Mexico softened the mass extinction of marine fauna at the end of the Paleocene 1 1
The mouth of the Mississippi River, which flows into the Gulf of Mexico: if geological processes had not turned the rivers of North America to the south, marine life in the bay would have been hard

The consequences of warming were especially noticeable on the World Ocean: currents and salinity levels changed, polar ice melted, and water was strongly acidified due to the dissolution of carbon dioxide in it.

Some animals were able to adapt to such changes, but others, such as foraminifera, failed the “strength test” and became victims of a mass extinction that wiped out up to 50 percent of their species diversity.

Not everywhere the effects of the extinction were felt the same way, and some places in the world’s oceans, such as the Gulf of Mexico, suffered relatively little. A group of American scientists decided to find out the reason. To do this, they studied samples of ancient deposits collected during the drilling of oil and gas wells.

All of the samples contained fossils of radiolarians, planktonic microorganisms whose skeletons are usually made of silica. Judging by their abundance, during the thermal maximum, these crumbs flourished in the waters of the bay, while many other parts of the Atlantic Ocean became almost uninhabitable.

Probably, their survival was affected by river runoff, because the Mississippi, one of the world’s most full-flowing rivers, flows into the Gulf of Mexico.

But this was not always the case: about 20 million years before the start of warming, the Rocky Mountains began to rise, which redirected the riverbeds towards the Gulf of Mexico.

With rising global temperatures, mountain glaciers began to melt, as a result, the runoff of nutrients increased, and in the mouths of the rivers, the bay was literally chock-full of food for microscopic plankton.

Probably, the influx of fresh water weakened the acidification of the sea, and due to the continued connection with the Atlantic Ocean, the salinity level did not fall below critical values.

Special conditions of the Gulf of Mexico softened the mass extinction of marine fauna at the end of the Paleocene 2 1
Some types of radiolarians: the abundance of these microorganisms indicates an excess of nutrients and normal salinity of the water

Of particular interest to the question of how marine life survived ancient global warming is the current climate situation. Considering that humanity emits about 10 billion tons of carbon into the environment per year, we can reach the level of the Paleocene-Eocene thermal maximum in just a thousand years.

Perhaps the inhabitants of unique places like the Gulf of Mexico will be able to survive another test. But the inhabitants of the rest of the oceans may not be so lucky.


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