End-Permian Marine Mass Extinction Caused by Increased Temperatures, Oxygen Loss: Study

Some 252 million years ago, intense volcanic activity belched massive volumes of greenhouse gasses into the atmosphere and triggered rapid changes to the climate, which resulted in the end-Permian mass extinction, the largest mass extinction event in Earth’s history. Nearly 96% of all marine species were wiped out during the extinction even, followed by millions of years when life had to multiply and diversify once more. According to a new study published in the journal Science, the extinction in the oceans was caused by global warming that left marine animals unable to breathe; as temperatures rose and the metabolism of the animals sped up, the warmer waters could not hold enough oxygen for them to survive.

Schematic illustration of temperature-dependent hypoxia as a driver of the end-Permian marine mass extinction. Greenhouse gas forcing in a model of Earth’s climate at the end of the Permian drives ocean warming (contours) and oxygen loss that match geochemical proxy data. Ocean warming raises the organismal oxygen demand amid declining supply. The resulting loss of aerobic habitat for diverse physiologies induces a mass extinction in model animal types (line) whose geographic signature — increased severity outside of the tropics — is consistent with reconstructions from the marine fossil record (circles). Image credit: J. Penn / C. Deutsch / E. Haeckel / W. Kaveney / H. Fjeld / J. White.

“This is the first time that we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, which then allows us to make predictions about the causes of extinction in the future,” said study lead author Justin Penn, a doctoral student at the University of Washington.

Penn and his colleagues from the University of Washington and Stanford University investigated the roles of rapid greenhouse warming and the accompanying loss of oxygen in the ocean, the two best-supported aspects of end-Permian environmental change.

They simulated the dynamics of the ancient extinction using an Earth system model coupled with data representing a diverse collection of living species to simulate the effects of end-Permian ocean warming and deoxidation on habitat loss and animal survival.

The results revealed distinct patterns of extinction — animals that lived in higher latitudes were more prone to extinction.

As waters warmed and oxygen became scarce, their low tolerance for hypoxic environments meant they had nowhere to run.

Tropical marine animals, pre-adapted to low-oxygen and high temperatures, were better-equipped to survive the environmental changes.

“The signature of that kill mechanism, climate warming and oxygen loss, is this geographic pattern that’s predicted by the model and then discovered in the fossils,” Penn said.

“The agreement between the two indicates this mechanism of climate warming and oxygen loss was a primary cause of the extinction.”

According to the team, the situation in the late Permian — increasing greenhouse gases in the atmosphere that create warmer temperatures on Earth — is similar to today.

“Under a business-as-usual emissions scenarios, by 2100 warming in the upper ocean will have approached 20% of warming in the late Permian, and by the year 2300 it will reach between 35 and 50%,” Penn said.

“This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change.”

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Justin L. Penn et al. 2018. Temperature-dependent hypoxia explains biogeography and severity of end-Permian marine mass extinction. Science 362 (6419): eaat1327; doi: 10.1126/science.aat1327