Marine productivity changes during the end-Permian crisis and Early Triassic recovery

The latest Permian mass extinction (LPME) coincided with major changes in the composition of marine plankton communities, yet little is known about concurrent changes in primary productivity. Earlier studies have inferred both decreased and increased productivity in marine ecosystems immediately following the end-Permian crisis. Here, we assess secular and regional patterns of productivity variation during the crisis through an analysis of the burial fluxes of three elemental proxies: total organic carbon (TOC), phosphorus (P), and biogenic barium (Babio). Primary productivity rates appear to have increased from the pre-crisis Late Permian through the Early Triassic in many parts of the world, although the South China Craton is unusual in exhibiting a pronounced decline at that time. Most of the 14 Permian–Triassic study sections show concurrent increases in sediment bulk accumulation rates, suggesting two possible influences linked to subaerial weathering rate changes: (1) intensified chemical weathering, resulting in an increased riverine flux of nutrients that stimulated marine productivity, and (2) intensified physical weathering, leading to higher fluxes of particulate detrital sediment to continental shelves, thus enhancing the preservation of organic matter in marine sediments. An additional factor, especially in the South China region, may have been the intensified recycling of bacterioplankton-derived organic matter in the ocean-surface layer, reducing the export flux rather than primary productivity per se. The ecosystem stresses imposed by elevated fluxes of nutrients and particulate sediment, as well as by locally reduced export fluxes of organic matter, may have been important factors in the ~ 2- to 5-million-year-long delay in the recovery of Early Triassic marine ecosystems.