二叠纪-三叠纪大灭绝期间的海洋损失是有史以来最严重的。所有群体都受到严重影响,尤其是在底栖动物中(例如腕足类,珊瑚,苔藓虫,有孔虫,ostracods)。浮游生物种群发生了根本性的变化,真核藻类被固氮细菌取代,绿硫细菌,还原硫酸盐的细菌和Prasinophytes。边界剖面的详细研究,尤其是那些在中国南方的人,已经将危机解决到横跨二叠纪-三叠纪边界的55公里区间。许多损失发生在此间隔的开始和结束时,绘制了两阶段灭绝的图片。许多地球化学研究支持了对灭绝的了解,这些研究允许研究各种拟议的灭绝机制。在全球大多数部分都可以看到从含氧到缺氧-缺氧条件的转变,尽管强度和时间显示出区域可变性。海洋通风减少与温度迅速上升同时发生,许多灭绝情景将损失归因于缺氧和高温。其他杀死机制包括海洋酸化,地球化学代理人对此提供了相互矛盾的支持,更不可能,淤积(在大量陆源沉积物下埋葬),缺乏实质性沉积学证据。二叠纪末期灾难性变化的最终驱动因素很可能是西伯利亚陷阱爆发及其相关的二氧化碳排放,并带来变暖等后果,海洋停滞和酸化。西伯利亚火山活动引起的火山冬季事件也与危机有关,但是这些事件的短期性质(<几十年)和危机期间迅速变暖的压倒性证据使这成为不太可能的原因。最后,虽然灭绝在赤道纬度地区得到了很好的研究,在北半球纬度发现了不同的历史,包括较早的危机,值得进一步研究,以充分了解二叠纪-三叠纪灭绝的过程和原因。
The marine losses during the Permo-Triassic mass extinction were the worst ever experienced. All groups were badly affected, especially amongst the benthos (e.g. brachiopods, corals, bryozoans, foraminifers, ostracods). Planktonic populations underwent a fundamental change with eukaryotic algae being replaced by nitrogen-fixing bacteria, green-sulphur bacteria, sulphate-reducing bacteria and prasinophytes. Detailed studies of boundary sections, especially those in South China, have resolved the crisis to a ∼55 kyr interval straddling the Permo-Triassic boundary. Many of the losses occur at the beginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has been supported by numerous geochemical studies that allow diverse proposed extinction mechanisms to be studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections globally, although the intensity and timing shows regional variability. Decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attribute the losses to both anoxia and high temperatures. Other kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation (burial under a massive influx of terrigenous sediment) which lacks substantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the Permian was likely Siberian Trap eruptions and their associated carbon dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Siberian volcanism have also been linked to the crisis, but the short-term nature of these episodes (
纬度多样性梯度(LDG)被认为是最普遍的,当今生物多样性的全球格局。然而,控制机制已被证明是困难的,因为许多潜在的驱动因素共同在空间中。地质记录为了解驱动LDG的机制提供了一个独特的机会,为深层生物地理动力学提供了一个直接窗口。在这里,我们使用了一个包含52,318次海洋化石的综合数据库,以表明在二叠纪-三叠纪大灭绝期间,LDG的形状发生了很大变化,从显示出明显的热带峰到平坦的LDG。平坦的LDG持续了整个三叠纪早期(〜5My),然后在中三叠纪恢复为现代形状。全球普遍存在的极端环境,尤其是戏剧性的变暖,可能通过起源和极地迁移导致低纬度地区的选择性灭绝和高纬度地区的多样性积累,这些加在一起构成了早三叠纪的平坦LDG。
The latitudinal diversity gradient (LDG) is recognized as one of the most pervasive, global patterns of present-day biodiversity. However, the controlling mechanisms have proved difficult to identify because many potential drivers covary in space. The geological record presents a unique opportunity for understanding the mechanisms which drive the LDG by providing a direct window to deep-time biogeographic dynamics. Here we used a comprehensive database containing 52,318 occurrences of marine fossils to show that the shape of the LDG changed greatly during the Permian-Triassic mass extinction from showing a significant tropical peak to a flattened LDG. The flat LDG lasted for the entire Early Triassic (∼5 My) before reverting to a modern-like shape in the Middle Triassic. The environmental extremes that prevailed globally, especially the dramatic warming, likely induced selective extinction in low latitudes and accumulation of diversity in high latitudes through origination and poleward migration, which combined together account for the flat LDG of the Early Triassic.