Fossilized pollen provides a glimpse at the end of the Permian extinction

Amazing stuff!

"Chemical clues in fossilized pollen grains suggest the world’s greatest mass extinction was a sunny affair ... As the Permian period gave way to the Triassic period about 250 million years ago, massive volcanic eruptions in present-day Siberia triggered a cataclysmic combination of greenhouse gas emissions, widespread mercury pollution, and a host of other atmospheric disturbances. Yet the full picture remains murky, including the possibility that damage to the ozone layer may have cooked many of the species already struggling to survive concurrent calamities ...

To investigate, Fraser and his colleagues turned their attention to tiny grains of fossilized pollen from southern Tibet. This collection contains around 800 pollen grains that come from the ancient relatives of ferns and conifers—plant types which survived the extinction event—and date back to time points spanning the Permian-Triassic boundary period. The tough outer coating of the pollen grains not only helped them stand the test of time in the fossil record, but also preserved traces of para-coumaric acid and ferulic acid. These phenolic compounds absorb ultraviolet B light, which helped shield the pollen from harmful solar radiation. Using Fourier transform infrared microspectroscopy, the researchers found that the abundance of UVB-absorbing compounds in their pollen-based chronology spiked around the same time as mercury and other signs of violent volcanic activity did. ..."

From the abstract:

"Land plants can adjust the concentration of protective ultraviolet B (UV-B)–absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to ambient UV-B flux. To infer changes in UV-B radiation flux at Earth’s surface during the end-Permian mass extinction, we analyze UAC abundances in ca. 800 pollen grains from an independently dated Permian-Triassic boundary section in Tibet. Our data reveal an excursion in UACs that coincide with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon and mercury cycle perturbations, and ozone layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling ecological driver for the terrestrial mass extinction."

Fossilized pollen provides a glimpse of Earth’s broiling past UV-absorbing phenolic compounds preserved in pollen grains point to powerful radiation during the Permian extinction

Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction (open access)

Phenolic compounds preserved in the tough outer coating of Alisporites tenuicorpus pollen grains provide a glimpse of scorching solar radiation during Earth’s largest mass extinction.