20 Million Years After The Cambrian Explosion, A Poisonous Gas Wave Wiped Out Nearly Half Of All Sea Life On Earth, According To Recent Research
Twenty million years after the Cambrian explosion, something lethal wiped out almost half of all sea life in the world.
For years, it was believed that the mass death event was caused by low-oxygen conditions triggered by the boom in the population of Cambrian life.
When the plants and animals died, their decomposing organic matter floated down to the seafloor and sucked oxygen out of the water.
But now, scientists have figured out the real culprit. According to a study published in the Geophysical Research Letters, the sudden die-off may have been caused by a poisonous wave of chemical gas called hydrogen sulfide.
A geochemist at Northwest University in Xi’an, China, named Chao Chang, led a team of researchers to the Yangtze Platform, a plateau in southern China that used to be underwater.
They were in search of molybdenum, a chemical element that allowed them to get a clearer picture of ocean conditions millions of years ago.
“Molybdenum (Mo) isotopes can be used to track global marine redox states in ancient oceans. Herein, new Mo isotope data revealed transitory expansion of sulfidic waterbodies in the global ocean at the major mass extinction levels,” wrote the study’s authors.
High concentrations of molybdenum can be associated with higher amounts of hydrogen sulfide. After analyzing the samples taken from the ancient mass extinction period, they found that the samples contained high levels of molybdenum, indicating that there must’ve been hydrogen sulfide in the water.
It is still unclear as to what exactly prompted the spread of the toxic gas, but the prevailing theory is that the deficit in oxygen was a result of a bunch of organic matter sinking to the ocean floor, providing a feast for trillions of microbes.
Andrei Armiagov – stock.adobe.com – illustrative purposes only, not the actual sea turtle
As the microbes munched away, they also might’ve consumed sulfate, which naturally occurs in seawater.
But since there were so many microbes ingesting sulfate and then releasing it as hydrogen sulfide, they managed to fill the water with the gas, making conditions harmful to a vast number of sea creatures.
“Sulfidic waters enriched in [hydrogen sulfide] are lethal for marine animals. Therefore, expanded sulfidic waterbodies in the global ocean could have served as a major driver for the mass extinction event,” concluded the study’s authors.
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