Oxygen depletion constitutes a major threat to lake ecosystems and the services they provide. Most of the world’s lakes are located >45° N, where accelerated climate warming and elevated carbon loads might severely increase the risk of hypoxia, but this has not been systematically examined. Here analysis of 2.6 million water quality observations from 8,288 lakes shows that between 1960 and 2022, most northern lakes experienced rapid deoxygenation strongly linked to climate-driven prolongation of summer stratification. Oxygen levels deteriorated most in small lakes (<10 ha) owing to their greater volumetric oxygen demand and surface warming rates, while the largest lakes gained oxygen under minimal stratification changes and improved aeration at spring overturns. Seasonal oxygen consumption rates declined, despite widespread browning. Proliferating anoxia enhanced seasonal internal loading of C, P and N but depleted P long-term, indicating that deoxygenation can exhaust redox-sensitive fractions of sediment nutrient reservoirs.

氧气耗尽对湖泊生态系统及其提供的服务构成重大威胁。世界上大多数湖泊位于北纬 45°以上，气候变暖加速和碳负荷升高可能会严重增加缺氧风险，但这一点尚未得到系统研究。对 8,288 个湖泊的 260 万个水质观测结果的分析表明，1960 年至 2022 年间，大多数北方湖泊经历了快速脱氧，这与气候驱动的夏季分层的延长密切相关。小湖泊（<10公顷）的氧气水平恶化最为严重，因为它们的需氧量较大，地表变暖速度也较大，而最大的湖泊则在最小的分层变化和春季翻转时通气改善的情况下获得了氧气。尽管褐变现象普遍存在，但季节性耗氧量却有所下降。增殖性缺氧增强了碳、磷和氮的季节性内部负荷，但长期消耗了磷，这表明脱氧可以耗尽沉积物营养库中氧化还原敏感的部分。