Extreme warming intensified lacustrine deoxygenation and methane cycling during the Paleocene-Eocene Thermal Maximum

Lakes are critical sentinels of climate change, yet their responses to rapid warming remain poorly understood. Here we present organic geochemical data of lacustrine sediments from eastern China during the Paleocene-Eocene Thermal Maximum (56 million years ago) to unravel environmental and biotic responses to rapid warming. Organic geochemical proxies indicate ≥7 °C continental warming in East Asia, triggering cascading effects including intensified stratification, bottom-water deoxygenation, eutrophication, and methanogenesis. These processes, evidenced by isotopic, productivity, and redox proxies, parallel modern lake responses to anthropogenic forcing. During the Paleocene-Eocene Thermal Maximum, elevated methane emissions from lacustrine systems likely amplified warming through positive carbon-cycle feedbacks. Our findings highlight lakes as one of potential dynamic amplifiers of carbon cycle perturbations, providing critical insights into freshwater ecosystem resilience in a warming world. This deep-time perspective underscores the vulnerability of modern lakes to cascading ecological disruptions, informing models of ecosystem resilience and carbon-climate interactions under sustained warming. Lakes in eastern China could potentially amplify carbon cycle perturbations during the Paleocene-Eocene Thermal Maximum, highlighting their vulnerability to ecological disruptions, according to analysis of organic geochemical data of lacustrine sediments.