The National High Magnetic Field Laboratory tests rock samples for thallium isotopes. Credit: Stephen Bilenky/National High Magnetic Field LaboratoryMany of the life forms on Earth were dying two hundred fifty-two millions years ago.More than 96 percent and 70% of planet's terrestrial species were extinct in an event that marked end to the Permian Period. It was the most significant extinction in Earth history.Researchers at Florida State University have discovered that the extinction coincided a sudden increase and subsequent decrease in ocean oxygen content. Nature Geoscience published their findings.Sean Newby, a FSU graduate research assistant, said that there has been previous work that indicates the environment is becoming less oxygenated. However, it has been hypothesized that this gradual change will occur. "We were shocked to see this rapid oxygenation event coincide with the beginning of the extinction, and then a return back to reducing conditions."Scientists had previously observed a gradual decline in oxygen during the extinction. However, the sudden increase at the start of the extinction was new. Researchers believe that oxygenation took place over just a few tens or thousands of years. This is a short period compared to the many millions of years of Earth's geological past.Newby stated that the geological record shows that it was almost instantaneous. You can then compare this to modern, human-induced global warming, which is causing huge, rapid changes in fractions of a second compared to the mass extinction.Although the exact cause of the ocean oxygenation spike is not known, the researchers believe that the continuous eruption of at most several hundred thousand years of an enormous volcanic region caused a short cooling and the subsequent spike and crash in marine oxygenation.Although ancient marine oxygen levels showed a declining trend before the eruption and continued to decline afterward, it was the abrupt shift back and forth in the earth's atmosphere and the long-term deficiency of oxygen that proved to be more harmful to life than the gradual decrease. The volcanic eruption released carbon dioxide, which caused the Earth's atmosphere heat up and lowered oxygen levels in the oceans. This made the oceans more inhospitable over millions of years.It is not possible to measure atmospheric or marine oxygen levels in the past. The research team measured thallium Isotopes instead, which provided indirect information that helped to understand marine oxygen levels in the past.Researchers plan to examine other ancient extinctions to determine if there were similar dramatic swings of oxygen with any of those mass-extinctions. This could have modern-day consequences as climate change and increased nutrients discharge reduce the amount of oxygen in the ocean."It's more than just the loss of oxygen within the modern ocean," stated Jeremy Owens, associate professor in Department of Earth, Ocean and Atmospheric Science and co-author of the paper. "The loss oxygen is important because organisms currently living in the ocean are adapted to high oxygen. However, if there's low oxygen, there may be organisms that can adapt. Any rapid fluctuations in either direction will cause an impact."This work was done by researchers from Florida State University, Western Carolina University, and the University of Cincinnati.Continue reading Volcanic activity and declining ocean oxygen caused mass extinctions of ancient organisms.More information: Transient ocean oxygenation at end-Permian mass extinction onset shown by thallium isotopes, www.nature.com/articles/s41561-021-00802-4 Journal information: Nature Geoscience Transient ocean oxygenation at end-Permian mass extinction onset shown by thallium isotopes, DOI: 10.1038/s41561-021-00802-4
