Recurring marine phosphorus spikes during major palaeozoic mass extinctions and climate change

Mass extinctions in the early Palaeozoic have been attributed to global climate change and ocean anoxia with elevated phosphorus (P) proposed as a key driver. However, this hypothesis has lacked geochemical support due to the absence of proxies that can reconstruct changes in marine P availability. Focusing on the Late Ordovician Mass Extinction (LOME) and the Late Devonian Mass Extinction (LDME), we present carbonate-associated phosphate (CAP) data from seven globally distributed sections, providing a proxy record for seawater P variation across these events. Our data reveal short-lived, globally coherent P pulses that coincided with both events. These transient P surges align with biodiversity loss, widespread anoxia, and seawater temperature declines, suggesting a link between P flux, ocean anoxia, and global climate shifts, as supported by biogeochemical model results. These findings provide an empirical connection between brief marine P pulses and ecological crises during the LOME and LDME.