Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany.
University of Exeter, Camborne School of Mines, College of Engineering, Mathematics and Physical Sciences, Penryn, Cornwall, United Kingdom.
PLoS One. 2020 Dec 9;15(12):e0242331. doi: 10.1371/journal.pone.0242331. eCollection 2020.
The Toarcian Oceanic Anoxic Event (TOAE; Early Jurassic, ca. 182 Ma ago) represents one of the major environmental disturbances of the Mesozoic and is associated with global warming, widespread anoxia, and a severe perturbation of the global carbon cycle. Warming-related dysoxia-anoxia has long been considered the main cause of elevated marine extinction rates, although extinctions have been recorded also in environments without evidence for deoxygenation. We addressed the role of warming and disturbance of the carbon cycle in an oxygenated habitat in the Iberian Basin, Spain, by correlating high resolution quantitative faunal occurrences of early Toarcian benthic marine invertebrates with geochemical proxy data (δ18O and δ13C). We find that temperature, as derived from the δ18O record of shells, is significantly correlated with taxonomic and functional diversity and ecological composition, whereas we find no evidence to link carbon cycle variations to the faunal patterns. The local faunal assemblages before and after the TOAE are taxonomically and ecologically distinct. Most ecological change occurred at the onset of the TOAE, synchronous with an increase in water temperatures, and involved declines in multiple diversity metrics, abundance, and biomass. The TOAE interval experienced a complete turnover of brachiopods and a predominance of opportunistic species, which underscores the generality of this pattern recorded elsewhere in the western Tethys Ocean. Ecological instability during the TOAE is indicated by distinct fluctuations in diversity and in the relative abundance of individual modes of life. Local recovery to ecologically stable and diverse post-TOAE faunal assemblages occurred rapidly at the end of the TOAE, synchronous with decreasing water temperatures. Because oxygen-depleted conditions prevailed in many other regions during the TOAE, this study demonstrates that multiple mechanisms can be operating simultaneously with different relative contributions in different parts of the ocean.
早侏罗世托阿尔阶大洋缺氧事件（TOAE；约 1.82 亿年前）是中生代主要的环境干扰事件之一，与全球变暖、广泛缺氧以及全球碳循环的严重扰动有关。长期以来，人们一直认为与升温有关的缺氧是导致海洋灭绝率升高的主要原因，尽管在没有缺氧证据的环境中也记录了灭绝事件。我们通过将早托阿尔阶底栖海洋无脊椎动物的高分辨率定量动物群出现与地球化学示踪剂数据（δ18O 和 δ13C）相关联，来解决含氧生境中变暖与碳循环扰动的作用问题，该生境位于西班牙伊比利亚盆地。我们发现，壳层的 δ18O 记录所推断的温度与分类和功能多样性以及生态组成呈显著相关，而我们没有发现将碳循环变化与动物群模式联系起来的证据。TOAE 前后的局部动物群在分类和生态上是不同的。大多数生态变化发生在 TOAE 的开始，与水温的增加同步，涉及到多个多样性指标、丰度和生物量的下降。TOAE 期间经历了腕足动物的完全更替和机会主义物种的优势，这突显了在西特提斯洋其他地方记录的这种模式的普遍性。TOAE 期间的生态不稳定性表现为多样性和个别生活方式的相对丰度的明显波动。在 TOAE 结束时，水温下降，快速恢复到具有生态稳定性和多样性的 TOAE 后动物群组合。由于在 TOAE 期间许多其他地区缺氧条件普遍存在，因此这项研究表明，多个机制可以同时作用，在海洋的不同区域具有不同的相对贡献。
