More than 250 million years ago, life on Earth almost disappeared.
In an event known as the Permian-Triassic extinction, about 95% of all species on the planet were wiped out. This was not the only extinction event in Earth’s long history, but it is one that has been particularly puzzling to scientists.
“Usually a mass extinction event happens (a meteorite hits or there’s a big volcanic eruption) and things disappear, but then they recover relatively quickly,” says Clément Bataille, associate professor in the department of earth and environmental sciences University of Ottawa environment. “What happened in this case is that for six million years after this mass extinction, nothing recovered.”
For decades, researchers have been trying to figure out why it took so long for life to return to Earth after the catastrophic Permian-Triassic extinction. Now, new research by Bataille and colleagues suggests that this prolonged recovery was due to the extinction of important microorganisms.
Looking for answers
Bataille, along with University of North Carolina professor Xiao-Ming Liu and doctoral student Cheng Cao (now a postdoctoral fellow at Nanjing University), set out to find answers to this question more than six years ago. Their findings appeared last month in the journal Nature Geoscience, in a paper co-authored with six other researchers from the United States, China and Denmark, along with an accompanying editorial highlighting the significance of their findings.
Bataille uses isotopes in his research to track things like the migration of existing animals. By doing this, it is easier to understand how pollution can be traced back to its sources.
Initially, the team believed that the answer to their questions might be found in a process called weathering. The Earth has maintained its habitability by regulating the amount of carbon dioxide that ends up in the air through the process of weathering.
‘The results were very surprising. I got these results six years ago, but we didn’t have the framework to explain them.”
— Prof. Clément Bataille, Earth scientist, University of Ottawa
“When we started the study, we wanted to say, OK, maybe something happened with this weathering process that was affecting the climate,” Batatille said.
However, when they looked at the mass extinction, Bataille and the other researchers realized that there had to be something else causing the isotope values to be so low.
“The results were very surprising. I got these results six years ago, but we didn’t have the framework to explain the results,” says Bataille, adding that his team had to wait for the field to evolve before they could confirm the results. your suspicions
They found that the opposite reaction was happening, creating reverse weathering. This happens when the carbon is released into the atmosphere and not trapped by the rock, which explains why the isotope values decreased.
Bataille explains that our oceans today have very little or no silicon because tiny microorganisms, known as diatoms, use almost all the silicon in the oceans to make their shells.
“In the past, this microorganism had not yet evolved and there were some other microorganisms capable of making silicone shells called radiolaris,” said Bataille. “But they (the radiolarians) disappeared at the time of this great mass extinction: they were one of the first microorganisms to disappear.”
With this microorganism gone, silicon continued to accumulate and began to form into clay.
“Instead of trapping a molecule of CO2 in the ocean, it’s actually releasing a molecule of CO2,” Bataille said.
Earth was unable to return to a normal state of self-regulation, which may explain why it took so long for life to return to the planet. This process is similar to the greenhouse effect, in which CO2 is released into the atmosphere and warms the planet.
“Just because that microorganism disappeared, a small microorganism or a small group of microorganisms that were able to block everything and basically keep the old cycles in check, they’re no longer there,” Bataille said.
Research by Bataille and his colleagues can fill many gaps in knowledge about the era, says Hana Jurikova, a researcher at the University of St. Andrews in Scotland, which studies the co-evolution of climate, environment and life on Earth. Jurikova also wrote an accompanying editorial for the study. “It definitely drives us forward,” says Jurikova. “They’ve done the work that hadn’t been done and that was needed.”
This research does two important things to advance the field, he says.
“When I saw this (study), I was really excited, because I feel like it was a really important record that we’ve been missing for a long time.”
— Hana Jurikova, researcher, University of St. Andrews, Scotland
First, it provides scientists with a new lithium isotope record spanning the entire Permian period, something that is not easy to produce. “You have to be very careful when choosing your samples and examining them and also making sure that all your laboratory methods are really robust,” says Jurikova. “So when I saw this (studio), I was really excited, because I feel like it was a really important record that we’ve been missing for a long time.”
This is also the first evidence to suggest that the process of reverse weathering was happening in the Permian period, says Jurikova.
Now, it will be up to the researchers to continue to build on and test the findings of this study. “I think it’s really exciting evidence that has yet to be proven and we hope that further studies will prove it and follow it up,” says Jurikova.
Small but mighty
One important thing this study does is show how interconnected the entire planet is, says Bataille. Even small and seemingly insignificant life forms like diatoms can greatly influence the climate and habitability of the entire planet.
“I mean, we wouldn’t be here, we wouldn’t be able to breathe our oxygen if it wasn’t for the trees or the cyanobacteria that evolved millions or billions of years ago. Our oceans can’t be habitable without these little diatoms that we have today, and we don’t think about them, but they actually regulate all these biochemical cycles,” he says.
Attention is paid to the larger organisms that go extinct, Bataille says, but the tiny microorganisms that are crucial to our own survival are often overlooked in conservation conversations. This research is just one more example of why it’s important to take care of our planet and pay attention to small organisms that can have massive impacts, he says.
While the research of Bataille and his colleagues furthers our understanding of Earth, it also helps us better understand how extraterrestrial planets work. “There are many reasons to look at past climates, and one of them is simply to understand the habitability of planets,” says Bataille.
By having an understanding of the history of habitability on our own planet, we can more easily determine habitability elsewhere in the universe, Bataille says.
By using powerful new tools like the James Webb Space Telescope, scientists can look at the atmospheric composition of other planets and compare them to Earth’s atmosphere at different times in history. If a planet’s atmosphere is composed primarily of CO2, we can estimate that it acts similarly to Earth when its atmosphere was composed mostly of CO2, Bataille says.
“So that atmosphere tells you a lot about where the planet is in terms of habitability, because there is a very clear sequence of events in the history of our planets that lead to life, that lead to habitability,” he says
What follows
Bataille started on this project as a postdoctoral researcher in 2016, and since then his research interests have changed.
He’s still using isotopes to understand life on our planet in the distant past, but now he’s tracing animal migration patterns millions of years ago. This new research can help us better understand the extinction of animals, says Bataille.
“I think it’s a good insight into the independence that teachers have,” Bataille says, adding that she’s able to work on topics that interest her but also have relevance to important discussions about conservation and climate.