At the time of the Permian-Triassic boundary (roughly 252 million years ago), the largest mass extinction of the Phanerozoic occurred. Previous studies of this event have focused primarily on how it affected terrestrial vertebrates and marine invertebrates. A recent study has examined geological evidence of changes in the diversity and abundance of phytoplankton. Studying phytoplankton populations during this time has posed some difficulty in the past due to the fact that the fossil record of Permian-Triassic phytoplankton is not well preserved.

In the new study, sufficient material was gathered to evaluate changes in acritarch communities. ‘Acritarch’ refers to a large group of single-celled marine plankton of uncertain classification, and that could include the earliest known examples of eukaryotes. The team studied the diversity and abundance among eight genera and twenty-five species of these organisms in samples from southern China, and that represent the Upper Permian to the Lower Triassic. The results indicate that there were two extinction events across the Permian-Triassic boundary, the second of which was more severe.

The study, “Phytoplankton (acritarch) community changes during the Permian-Triassic transition in South China,” was published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. The work was supported by NASA Astrobiology through the Exobiology Program.