Department of Earth and Planetary Sciences, University of California, Riverside, Riverside, CA, USA.
Biogéosciences, UMR 6282, UBFC/CNRS, Université Bourgogne Franche-Comté, Dijon, France.
Nature. 2022 Aug;608(7923):523-527. doi: 10.1038/s41586-022-05018-z. Epub 2022 Aug 17.
The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O]) in the ocean. In turn, [O] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO). Here, by contrast, we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O]. We further identify the presence of state transitions in the global ocean circulation, which lead to extensive deep-ocean anoxia developing in the early Phanerozoic even under modern pO. Our finding that ocean oxygenation oscillates over stable thousand-year (kyr) periods also provides a causal mechanism that might explain elevated rates of metazoan radiation and extinction during the early Palaeozoic Era. The absence, in our modelling, of any simple correlation between global climate and ocean ventilation, and the occurrence of profound variations in ocean oxygenation independent of atmospheric pO, presents a challenge to the interpretation of marine redox proxies, but also points to a hitherto unrecognized role for continental configuration in the evolution of the biosphere.
海洋动物的早期进化和许多灭绝历史被认为是由海洋中溶解氧浓度 ([O]) 的变化驱动的。反过来，[O] 广泛认为主要由大气氧 (pO) 的地质历史决定。相比之下，在这里，我们通过一系列地球系统模型实验表明，显生宙期间的大陆重新排列如何驱动海洋氧合作用的深刻变化，并导致上洋和底栖 [O] 之间在时间上的基本解耦。我们进一步确定了全球海洋环流中存在状态转变，这导致即使在现代 pO 下，早期显生宙也会出现广泛的深海缺氧。我们发现海洋氧合作用在稳定的千年 (kyr) 周期上振荡，这为解释古生代早期后生动物辐射和灭绝率的升高提供了一个因果机制。在我们的模型中，全球气候和海洋通风之间没有任何简单的相关性，以及海洋氧合作用的深刻变化独立于大气 pO，这对海洋氧化还原示踪剂的解释提出了挑战，但也指出了大陆配置在生物圈演化中迄今为止尚未被认识到的作用。
