Fossilized crinoids, marine invertebrates that lived during the Permian Period, found in western Australia. Scientists say the Great Dying, which wiped out 96 percent of all life in the oceans, was caused by global warming, which deprived the oceans of oxygen.John Cancalosi, via Getty Images
The New Your Times has a good article about the Permian Mass Extinction on Carl Zimmer's Matter blog. The story is in response to a new study published in Science. No real surprises as climate change was the driving force.
And we may be repeating the process, the scientists warn. If so, then climate change is “solidly in the category of a catastrophic extinction event,” said Curtis Deutsch, an earth scientist at the University of Washington and co-author of the new study, published in the journal Science.
Researchers have long known the general outlines of Permian-Triassic cataclysm. Just before the extinctions, volcanoes in what is now Siberia erupted on a tremendous scale. The magma and lava that they belched forth produced huge amounts of carbon dioxide.
Once in the atmosphere, the gas trapped heat. Researchers estimate that the surface of the ocean warmed by about 18 degrees Fahrenheit. Some researchers argue that the heat alone killed off many species.
Others believe that the warmth reduced oxygen in the ocean, asphyxiating the species living there. Rocks from the mass extinction appear to have formed when at least some of the ocean was lacking oxygen.
In previous research, Dr. Deutsch has explored how living animals adapt to temperature and oxygen levels in the seas. Animals with a fast metabolism need a lot of oxygen, for example, and so they can’t live in parts of the ocean where oxygen falls below a certain threshold.
Warm water makes the challenge even more difficult. Warmer water can’t hold as much dissolved oxygen as cold water. Even worse, warm water can also increase an animal’s metabolism, meaning it requires more oxygen just to stay alive.
