Most people have heard of the extinction of the dinosaurs and many other animals that occurred approximately 65 million years ago. However, while cataclysmic, the loss of species was nothing compared to the Permian extinction, also known as the Great Dying, that occurred 250 million years ago. Incredibly, within a span of 200,000 years, roughly 95% of all marine animals and almost as many terrestrial animals went extinct. Even animals that were previously found in abundance or widely dispersed disappeared. What triggered the massive death of so many animals has been the subject of much speculation. Recent data, however, suggest that a combination of factors may be to blame.
As reported in The New York Times (Science: April 30, 2012), scientists studying thousands of marine fossils from the Permian period have concluded that cause of death was at the cellular level. Animals that could not maintain cellular homeostasis died. Scientists learned that marine animals had to cope quite quickly with too little oxygen and too much carbon dioxide in the water, and increased water temperature and acidity. Each factor amplified the effects of the others. Most marine animals could not adapt, leading to dramatic changes in marine fauna. For example, trilobites and most corals disappeared. Snails and bivalves (such as clams and scallops), which could cope with the changes, became the dominant organisms.
What triggered the event is not known, but researchers suspect a huge, sudden infusion of carbon. Most likely the massive volcanic explosions that formed the Siberian Traps in northern Russia released catastrophic amounts of carbon gas into the atmosphere and caused the resultant changes in the oceans. Unfortunately for us, the parallels between what happened 250 million years ago and what is happening in our oceans today are eerily similar. The concentration of carbon-based gases in the atmosphere is increasing rapidly. Ocean water temperatures and pH are rising. Large oxygen depleted areas can be found in most oceans. While the oceans of today are different from those of the Permian era and may be more resilient to the effects of a carbon infusion, worrisome signs abound. Corals, as they were 250,000 million years ago, may be most susceptible to the changes. Evidently, the effect of current human activity on the oceans is not too dissimilar from that of ancient massive volcanoes.
Noted by WVR, MD
*This filler excerpt can be found in the July 2012 Pediatrics print journal p. 107, or via online here.
