End-Permian Mass Extinction Revealed: Sulfide Stress and Temperature Advantage for Bivalves Over Brachiopods

A Shortwave episode examines the greatest loss of animal diversity in Earth's history, the end-Permian mass extinction. Stanford paleophysiology researcher Kemi Ashiniwa describes how massive volcanic activity in the Siberian traps released greenhouse gases, altering ocean chemistry and depleting oxygen. Through lab experiments comparing clams (bivalves) and brachiopods under low-oxygen, sulfide-rich, and variable-temperature conditions, the study finds brachiopods struggle with warming and sulfide, while bivalves cope with heat and toxic sulfide better. The research highlights the importance of interacting climate factors and how ancient natural experiments inform today’s climate challenges and biodiversity.

Introduction: The Great Dying and the Research Question

Shortwave explores the Permian-Triassic mass extinction, known as the Great Dying, about 251.9 million years ago, when volcanic activity in the area of today’s Siberian traps released massive greenhouse gases. This caused global warming and ocean deoxygenation, leading to the collapse of most species on land and in the sea. The central question is why certain groups survived while others disappeared, focusing on marine filter feeders, especially bivalves (clams) versus brachiopods (their distant shelled cousins).

"It's not just temperature that matters. It's not just oxygen that matters. All of these things together because their combined effects are so much worse." - Kemi Ashiniwa, paleophysiology graduate student, Stanford University