The oxygenation of the oceans took place thanks to the evolution of the first animals. This is the new thesis of some British researchers ready to revolutionize traditional theory
He is about to end up run over, his mother saves him
THEoxygenation of the oceans it took place thanks to the evolution of the first animals. It is the new thesis of some British researchers ready to revolutionize traditional theory, which says that it was an increase in atmospheric oxygen concentrations that led to oxygenation of the sea, thus triggering the evolution of animals.
Research conducted at the British University of Exeter, UK, e published in the journal Nature Geoscience, has therefore completely overturned the causal relationship between the appearance of the first animals and the increase in oxygen on Earth, whose levels up to 750 and 500 million years ago were very low.
Scientists examined thewas Neoproterozoic (which is the last of the three geological eras into which the Proterozoic is divided and which extends from 1000 million to 542 million years ago), considered a time of turbulent environmental change. Wide fluctuations in the carbon cycle from that time they have been associated with at least two great glaciations. There have also been huge changes in the state of the oceans and in the midst of this major environmental shift, increasingly complex life forms have evolved.
“For over 1,5 billion years before the first animals evolved, there were relatively high levels of oxygen in ocean surface waters, it was the dark depths of the ocean that were left without oxygen. We argue that the evolution of the first animals may have played a key role in the diffusion of oxygenation of the deep oceans, which in turn facilitated the evolution of more complex and more mobile animal forms ", explains Timothy M. Lenton, first signer of the article.
According to the Exeter scholars, the diffusion of sponges, filtering animals, would have reduced the quantities of finished organic residues at greater depths, where, on the other hand, the demand for oxygen was lowered, leading to an increase in its levels.
“The study - concluded Simon Poulton, co-author of the survey - provides a plausible mechanism for the oxygenation of the ocean without the need for a previous increase in atmospheric oxygen. And then he asks a question about the correctness of this long-accepted assumption. We currently do not know the answer to this question, which is ultimately the key to understanding how our planet evolved to its current habitable state. To have it, geochemists need to find new ways to decipher the oxygen levels on the early Earth ”.
Germana Carillo
Foto Credit: Nicholas J. Butterfield
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- World Oceans Day 2013
