SCIENCE – Microbes belching out poisonous gases exacerbated the largest extinction

Madrid, 20 (European Press)

A new study has found that tiny microbes that emit toxic fumes helped cause and prolong the largest mass extinction in Earth’s history.

In general, scientists believe that Siberian volcanoes that released greenhouse gases caused the mass extinction about 250 million years ago, at the end of the Permian period. The gases caused extreme warming, which in turn led to the extinction of 80% of all marine species, as well as many terrestrial species.

Until now, scientists have not been able to explain exactly how the heat caused these deaths. A new study led by the University of California Riverside, published in Nature Geoscience, shows that heat speeds up the metabolism of microbes, creating deadly conditions.

“After using the oxygen from the ocean to break down the organic matter, the microbes began to ‘breathe’ the sulfate and produced hydrogen sulfide, a gas that smells like rotten eggs and is toxic to animals,” said UC Riverside Earth system designer Dominic Hulse.

Being the photosynthesis agents in the ocean, the microbes and plants that make up the base of the food chain rot away, and other microbes consume oxygen quickly and leave little for larger organisms. In the absence of oxygen, the microbes consumed the sulfate and then expelled the toxic and wonderful hydrogen sulfide, or H2S, resulting in a more dangerous condition called euxinia. These conditions were maintained by the release of nutrients during decomposition, which encouraged the production of more organic matter that helped maintain this toxic, odorless cycle.

“Our research shows that the entire ocean was not a natural creature. These conditions started in the deepest parts of the water column,” said Hulse. “As temperatures rose, the euxinic areas became larger and more toxic and moved up the water column toward the shelf environment where most marine animals lived, poisoning them.”

Expansion of euxinic regions can be detected by chemical signatures in sediment samples.

Oxygen depletion is an ongoing problem today and will certainly get worse with future climate change. Euxinic water can be found in places like the 22-kilometer Dominguez Canal in Los Angeles County, where a warehouse fire in September 2021 unleashed ethanol. Ethanol killed the vegetation in the channel, which was decomposed and eaten by microbes. Then they produced hydrogen sulfide to toxic levels. Thousands of people living in the vicinity have reported vomiting, diarrhea, dizziness, insomnia, headaches, sneezing, and other symptoms.

Lessons from the ancient world can be important in understanding the processes that challenge modern oceans and waterways.

“It would be speculative to ride the ancient mass extinction event on the present planet,” said Hulse. “However, the study shows us that the ocean’s response to higher concentrations of carbon dioxide in the atmosphere may be an underestimate.”