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Life Returned Shortly After Mass Extinction, But Long-Term Biodiversity Suffered

December 22, 2012
Image Caption: Ammonoids peaked earlier after the vast mass extinction. Credit: University of Zurich

redOrbit Staff & Wire Reports – Your Universe Online

While it has long been assumed plant and animal life took a long time to recover following the largest mass extinction to date, researchers from the University of Zurich have discovered new evidence to suggest they may have bounced back sooner than previously believed.

The mass extinction in question took place at the end of the Permian geological period some 252 million years ago, and scientists had long believed it took roughly five million years for complex ecological communities to become re-established.

However, new research headed up by Hugo Bucher, a paleontologist at the institution, suggests some types of marine animals, including ammonoids and conodonts, had “already peaked” during the Early Triassic Period — approximately three to four million years earlier, the university announced on Friday.

Bucher and his colleagues created a model to study what the climate would have been like in the years following the mass extinction. They discovered the climate immediately afterwards was cooler. That was followed by a warming period, followed by another cooler period.

“The warmer climate, coupled with a high CO2 level in the atmosphere, initially gave rise to new, short-lived species,” the university explained. “In the longer term, however, this climate change had an adverse effect on biodiversity and caused species to become extinct.

Their work, which involved a chart of the temperature curves as well as fluctuations in atmospheric carbon dioxide levels, is detailed in the latest edition of the journal Nature Geoscience.

“For their climate reconstruction, Bucher and his colleagues analyzed the composition of the oxygen isotopes in conodonts, the remains of chordates that once lived in the sea,” the German institute said.

The researchers discovered the climate at the beginning of the Triassic Period was cool, which was followed by a “brief” period of extremely warm temperatures, then a return to the cooler conditions at the end of the Early Triassic Period, sometime between 247.9 and 245.9 million years ago. They then took this climatic information and applied it to see what impact it would have on the plant and animal life developing at that time.

“Biodiversity increased most in the cooler phases,” Bucher said. “The subsequent extremely warm phase, however, led to great changes in the marine fauna and a major ecological shift in the flora.”

According to the university, the researchers discovered the decline in biodiversity during the warmer times “correlates with strong fluctuations in the carbon isotope composition of the atmosphere.” Those fluctuations, as it turns out, were linked to CO2 gas-producing volcanic eruptions at the Siberian Large Igneous Province.

“Through the climatic changes, conodont and ammonoid faunae were initially able to recover very quickly during the Early Triassic as unusually short-lived species emerged. However, the removal of excess CO2 by primary producers such as algae and terrestrial plants had adverse effects in the long run: The removal of these vast amounts of organic matter used up the majority of the oxygen in the water,” the university said.

Many marine lifeforms ultimately died out due to that lack of oxygen, the researchers reported.

“Our studies reveal that greater climatic changes can lead to both the emergence and extinction of species. Thus, it is important to consider both extinction rates and the rate at which new species emerged,” Bucher concluded.


Source: redOrbit Staff & Wire Reports - Your Universe Online