Coupled increases in pelagic fish productivity and export productivity during the Paleocene-Eocene Thermal Maximum
In the authors' words
Ocean productivity is sensitive to climate change, and its decline in recent decades has profoundly impacted the biosphere. Yet its long-term trajectory under global warming remains a topic lacking consensus. To address this question, we use paired ichthyolith and marine barite accumulation rates to investigate marine productivity and associated biological responses during the Paleocene-Eocene Thermal Maximum. We find a widespread increase in pelagic fish productivity, particularly in the Pacific and North Atlantic, that closely tracks export productivity in trend and spatial pattern, suggesting this increase was fueled by enhanced carbon export from the surface ocean. Model simulations support the observed trend, demonstrating that under elevated pCO2 conditions, the effects of enhanced nutrient supply can outweigh the suppressive effects of ocean stratification on export productivity. Our findings highlight that the long-term response of marine productivity to sustained greenhouse warming may differ fundamentally from the short-term declines observed in the modern ocean. Increased productivity and fish abundance in the open ocean during extreme warming 56 million years ago contrasted with the short-term declines observed today, highlighting that marine ecosystems may respond differently to prolonged global warming.
Appeared: Friday, September 25. Nature Communications. Peer-reviewed journal.