Reconstructing pelagic fish productivity and export productivity during the Paleocene-Eocene Thermal Maximum

Ocean productivity is highly sensitive to climate change, but its future trend remains largely unknown, complicating projections for marine ecosystems and fisheries. Past warm climate events offer valuable analogs for understanding the long-term effects of anthropogenic warming on ocean productivity. The Paleocene–Eocene Thermal Maximum (PETM, about 56 million years ago) is one of the most pronounced global warming events in the Cenozoic era, triggered by massive and rapid injections of isotopically light carbon into the ocean-atmosphere system. While previous studies have evaluated ocean productivity during the PETM, proxy records and model results remain contradictory, and the response of fish productivity is also poorly constrained. Here we present global records of ichthyolith accumulation rates (IAR) from deep-sea sediment cores across the PETM. Our new data show the temporal and spatial evolution of pelagic fish productivity as well as the resilience in fish communities. These IAR data are then compared with export productivity estimates derived from marine barite accumulation rates (BAR) from the same or proximal sites to explore their correlation. Using the Earth system model cGENIE, we further conduct sensitive simulations to investigate the roles of elevated atmospheric pCO₂, changes in nutrient supply (internal and external), and ocean circulation in driving carbon export during the PETM. Through combining multi–proxy and model–informed analyses, this study provides an integrated perspective on how ocean productivity and fish communities reacted to abrupt warming, offering a critical long-term context for understanding the future of ocean ecosystems.