Separation of continents and lack of oxygen in the oceans

2024-09-04 23:10:48

In the Mesozoic era, the ocean was not full of life as we see it today, because there were several periods when its waters had no oxygen, which led to multiple mass extinctions. A recent study, published in Geology of Naturemay have found the trigger that caused this catastrophic chain of events.

The team was looking for evidence to support the theory that plate tectonics might play a role. This is because the Mesozoic, which lasted between 185 and 85 million years ago, was also the time when the supercontinent Gondwana broke up.

The researchers, who are from the University of Southampton (England), found evidence that, with the separation, multiple pulses of phosphorus were released from basalt (volcanic rock), at the bottom of the sea and on a continent.

On closer inspection, such pulses coincided with periods of oxygen scarcity in the oceans, known as oceanic anoxic events (OAEs), however, they needed to understand if the two were connected.

Gondwana may have helped eliminate oxygen in ancient oceans (Image: University of Southampton)

To test the theory, the researchers used a computer model, called the Earth System Model, to simulate the effect of phosphorus pulses on ocean chemistry. Then, they found that it recreated the sequence of OAEs.

Then, they had to understand how the abundance of phosphorus led to a lack of oxygen and, accordingly, changed the way marine life developed.

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Oceans in the past and the impact of phosphorus on the end of oxygen

• Phosphorus is one of the essential elements for life. It is involved in the formation of DNA and cell membranes, as well as being a key component of the cells’ main energy source, ATP;
• However, although the growth and productivity of marine organisms increased due to the phosphorus pulses, the productivity lost much more organic matter into the ocean;
• the decomposition of organic matter consumes oxygen, which, on this kind of scale, has a devastating effect.

“This process led to areas of the ocean becoming anoxic, or lacking oxygen, creating ‘dead zones’ where most marine life was lost,” explained study co-author Benjamin Mills, professor with Earth System Evolution at the University of Leeds (England), in confirmation.

Such an OAE was “like hitting a reset button on the planet’s ecosystems,” lead author Professor Tom Gernon said, adding that the separation of continents during evolution could have “major consequences.”

The oceans in the Mesozoic Era were much less welcoming (Image: Shutterstock)

The discoveries not only provide a deep understanding of how the close coupling between the solid Earth and the surface affected life in the past, but can also give scientists clues about the consequences of this coexistence in our future , even more so because of the oceans, right now. , they suffered a drop in their oxygen content.

“It’s amazing because a chain of events within Earth can affect the surface, often with devastating effects,” Gernon said. “The study of geological events provides valuable insights that will help us understand how the Earth may respond to future climate and environmental stresses,” he said.