The marine calcium (Ca) cycle is controlled by rates of continental weathering, seawater pH, and carbonate deposition on the seafloor and is linked to atmospheric CO₂, climate change, and marine biotic evolution. Here, we provide the first continuous seawater Ca isotope profile from conodont apatite in South China for the latest Permian to early Middle Triassic, revealing major fluctuations in the Early Triassic calcium cycle. Three episodes of decreasing conodont δ^44/40Ca (by 0.16–0.23‰) occurred around the Permian-Triassic, Smithian-Spathian, and Olenekian-Anisian boundaries. The first episode, coincident with a negative excursion of carbonate carbon isotopes, global warming, oceanic anoxia, enhanced weathering, and sea-level fall, was likely caused by a combination of volcanic CO₂ release, ocean acidification, a reduced skeletal carbonate sink, and enhanced weathering of shelf carbonates. The latter two episodes, coincident with positive excursions of carbon isotopes, global cooling, and oceanic anoxia, possibly resulted from upwelling-driven shelf acidification and reduced skeletal carbonate burial. All three events were associated with marine biotic diversity losses, demonstrating a link between the calcium cycle and mass extinctions.

海洋钙（Ca）循环受大陆风化，海水pH值和海底碳酸盐沉积速率的控制，并与大气CO ₂，气候变化和海洋生物演化有关。在这里，我们提供了华南牙形磷灰石从二叠纪到中三叠世早期的第一个连续海水Ca同位素分布，揭示了三叠纪早期钙循环的主要波动。在二叠纪—三叠纪，史密斯一—斯巴第，奥列尼克—阿尼西斯边界周围，发生了三个减少牙^{形体δ44/40} Ca（0.16-0.23‰）的事件。第一次发生可能与碳酸盐碳同位素的负偏移，全球变暖，海洋缺氧，风化加剧和海平面下降同时发生，可能是由于火山二氧化碳的综合作用所致。₂释放，海洋酸化，减少的骨架碳酸盐汇和增强的陆架碳酸盐的风化作用。后两种情况，与碳同位素，全球变冷和海洋缺氧的正漂移相吻合，可能是由上升流驱动的架子酸化和骨骼碳酸盐埋葬减少所致。所有这三个事件都与海洋生物多样性的丧失有关，表明了钙循环与生物灭绝之间的联系。