Biodiversity suffered several crises leading up to the final famous catastrophe that killed nearly 90% of the marine species on a global scale at the end of the Permian. Earlier episodes of water with a decreased oxygen content shoaling towards the surface may have killed marine organisms during the Late Permian reports a paper in Nature Communications this week. This suggests that the ocean environments experienced a long period of deterioration before the final extinction.

Shen and colleagues report on a sulphur isotope signal from sedimentary rocks in South China which suggests the incursion of usually deep low oxygen, high sulphur water near the surface. This water would have resulted in the loss of marine and bioturbating organisms causing significant biodiversity loss.