Science. – Fossil pollen reveals role of ultraviolet radiation in the largest extinction event – Publimetro México

Madrid, 6 (Europe Press)

The presence of these compounds indicates that this “sunscreen” played an essential role in the mass extinction event at the end of the Permian period, reveals new research published in the journal Science Advances.

The mass extinction event at the end of the Permian (250 million years ago) is the most severe of the five major mass extinction events, with the loss of approximately 80% of marine and terrestrial species. This catastrophic loss of biodiversity was the result of a paleoclimate emergency caused by volcanic activity on a continental scale that covers much of present-day Siberia.

Volcanic activity released massive amounts of carbon into the atmosphere that was trapped inside the Earth, causing widespread global warming.

Along with this global warming occurred the collapse of the Earth’s ozone layer. Support for this theory comes from the abundance of deformed spores and pollen grains attesting to the influx of mutagenic ultraviolet light.

Plants need sunlight for photosynthesis, but they need to protect themselves, especially their pollen, from the harmful effects of UV-B radiation. “To do this, plants load the outer walls of pollen grains with compounds that act like sunscreen to protect vulnerable cells and ensure successful reproduction. Without ‘sunscreen’ compounds, forests would have become sterile, leading to collapse,” explains Professor Barry Lomax of the University of Virginia. Nottingham (UK).

“We developed a method for detecting these phenolic compounds in fossil pollen grains (type Alisporites) retrieved from southern Tibet and detected much higher concentrations in those grains than during the late Permian mass extinction and peak phase of volcanic activity,” says Prof. LIU Feng from the Institute. Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS), who led the team.

The researchers found an increase in ultraviolet-B absorbent compounds (UACs) that coincided with an increase in mercury concentration and a decrease in carbon isotopes in late Permian sediments, suggesting a close temporal link between large-scale volcanic eruptions, and global carbon. Mercury cycle disturbances and ozone layer disruption.

Elevated levels of UV-B radiation have had long-term and far-reaching effects on the entire Earth system. Recent modeling studies have shown that higher UV-B stress reduces plant biomass and terrestrial carbon storage, exacerbating global warming.

In addition, the high concentration of phenolic compounds makes plant tissues less digestible, making the harsh environment more difficult for herbivores.

Dr. Wes Fraser concludes, “Volcanoes on such a catastrophic scale affect every aspect of the Earth system, from direct chemical changes in the atmosphere, through changes in rates of carbon sequestration, to reducing the amount of nutritious food sources available to our animals.” from Oxford Brookes University in the United Kingdom.