Oxygen deprivation and hydrogen sulfide toxicity are considered potent kill mechanisms during the mass extinction just before the Permian–Triassic boundary (~251.9 million years ago). However, the mechanism that drove vast stretches of the ocean to an anoxic state is unclear. Here, we present palaeoredox and phosphorus speciation data for a marine bathymetric transect from Svalbard. This shows that, before the extinction, enhanced weathering driven by Siberian Traps volcanism increased the influx of phosphorus, thus enhancing marine primary productivity and oxygen depletion in proximal shelf settings. However, this non-sulfidic state efficiently sequestered phosphorus in the sediment in association with iron minerals, thus restricting the intensity and spatial extent of oxygen-depleted waters. The collapse of vegetation on land immediately before the marine extinction changed the relative weathering influx of iron and sulfate. The resulting transition to euxinic (sulfidic) conditions led to enhanced remobilization of bioavailable phosphorus, initiating a feedback that caused the spread of anoxic waters across large portions of the shelf. This reconciles a lag of >0.3 million years between the onset of enhanced weathering and the development of widespread, but geographically variable, ocean anoxia, with major implications for extinction selectivity.

在二叠纪-三叠纪界线之前（约2.519亿年前），大规模灭绝期间，氧气剥夺和硫化氢毒性被认为是有效的杀灭机制。但是，将大片海洋带入缺氧状态的机制尚不清楚。在这里，我们介绍了来自斯瓦尔巴特群岛的一个海洋测深样带的古氧化还原和磷形态数据。这表明，在灭绝之前，由西伯利亚圈套火山带动的风化作用增强了磷的涌入，从而增强了近海陆架环境中的海洋初级生产力和氧气消耗。但是，这种非硫化状态有效地将沉积物中的磷与铁矿物质结合起来，从而限制了缺氧水的强度和空间范围。在海洋灭绝之前，陆地上植被的崩溃改变了铁和硫酸盐的相对风化涌入。由此导致的向富氧（硫化物）条件的转变导致增强了生物利用磷的迁移，从而引发了一种反馈，导致缺氧水在架子的大部分区域扩散。这使气候变暖的开始与广泛但地理上可变的海洋缺氧的发展之间的滞后时间缩短了30万年，这对灭绝选择性具有重要意义。引发引起缺氧水在架子的大部分区域扩散的反馈。这使气候变暖的开始与广泛但地理上可变的海洋缺氧的发展之间的滞后时间缩短了30万年，这对灭绝选择性具有重要意义。引发引起缺氧水在架子的大部分区域扩散的反馈。这使气候变暖的开始与广泛但地理上可变的海洋缺氧的发展之间的滞后时间缩短了30万年，这对灭绝选择性具有重要意义。