Reef coral calcification and climate dynamics during the Eocene greenhouse (EOCENE)

始新世温室（EOCENE）期间的珊瑚礁珊瑚钙化和气候动态

• 批准号: 468545550
• 负责人: Professor Dr. Thomas Brachert
• 金额: --
• 依托单位: Institut für Geologie, Mineralogie und Geophysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/468545550?language=en
• 关键词: Reef; coral; calcification; climate; dynamics

Globally rising ocean temperatures and ocean acidification pose a threat to tropical shallow-water coral reefs. Yet, the acclimation potential of reef corals is largely unknown. Remarkably, no analogue data of heat stress and bleaching exist from warm periods of the geological past, such as the Eocene defined by SPP2299. Here, we propose a study on reef corals from the globally hot middle and late Eocene (45 – 35 Ma; this project EOCENE). Our project has three principal research objectives, consistent with themes A and B of the SPP: (1) Produce multi-year time-series of SSTs and evaporation/precipitation at monthly resolution and document the operation of the coral – zooxanthella symbiosis. (2) Generate parallel physical calcification records and geochemical fingerprints of calcification performance, to explore the expression of and possible resistance to thermal and other stressors. (3) Determine whether events of partial mortality of the coral colonies occurring on quasi-decadal time-scales were due to bleaching events that happened during heatwaves. The results will be compared to findings from later warm periods in the Cenozoic (e.g. mid Pliocene), to place our results within the broader framework of climatic, oceanographic and (bio)geographic changes through the Cenozoic. To meet the project goals, we will study corals from France and England (Paris Basin) that are extremely unusual in their near-pristine, unaltered preservation. Fieldwork will serve to reconstruct growth habitats and to put specimens into a geochronological context. For the first time, classical X-radiography (densitometry) and geochemical proxies for conditions at the habitat and calcification fluid scales will be applied to corals of Eocene age. For further synergies, we started the Bochum-Berlin-Leipzig initiative. In this frame, STRESS will investigate the proxy documentation of bleaching events and DIAGENESIS will study preservation potentials of proxy data during incipient diagenesis. Dissemination of our findings to the broader public will be ensured through contribution to a documentary for public TV (Arte-TV/ZDF). Besides providing important constraints on Eocene mid-latitude climate, we will gain a unique insight into the early evolutionary stages of the light-enhanced calcification system in taxa that dominate today’s coral reefs (e.g. Porites) and the first analytical evidence for heat stress in coral ecosystems and bleaching in the geological past. This deep-time perspective from a world of climatic extremes will provide an alternative view on the mechanisms underlying coral resistance to the dual stress of future ocean warming and acidification. Moreover, insights into coral calcification will directly contribute to a long-running discussion on deep-sea carbonate dissolution at the onset of the Middle Eocene Climate Optimum having been a result of global calcification fluxes being partitioned more toward reef ecosystems on flooded continental shelves.

全球海洋温度上升和海洋酸化对热带浅水珊瑚礁构成威胁。然而，珊瑚礁的适应潜力在很大程度上尚不清楚。值得注意的是，地质历史温暖时期（例如 SPP2299 定义的始新世）不存在热应激和白化的模拟数据。在这里，我们提议对全球炎热的始新世中晚期（45 – 35 Ma；本项目始新世）的珊瑚礁进行研究。我们的项目有三个主要研究目标，与 SPP 的主题 A 和 B 一致：(1) 以月度分辨率生成海表温度和蒸发/降水的多年时间序列，并记录珊瑚 - 虫黄藻共生的运作情况。 （2）生成并行的物理钙化记录和钙化性能的地球化学指纹，探索对热和其他应激源的表达和可能的抵抗力。 (3)确定准十年时间尺度上发生的珊瑚群部分死亡事件是否是由于热浪期间发生的白化事件造成的。结果将与新生代后期温暖时期（例如上新世中期）的发现进行比较，将我们的结果置于整个新生代气候、海洋和（生物）地理变化的更广泛框架内。为了实现项目目标，我们将研究来自法国和英国（巴黎盆地）的珊瑚，这些珊瑚在近乎原始、未改变的保存方面极为不寻常。实地工作将有助于重建生长栖息地并将标本放入地质年代学背景中。经典的 X 射线照相（光密度测量）和地球化学代表栖息地条件和钙化流体尺度将首次应用于始新世珊瑚。为了进一步发挥协同作用，我们启动了波鸿-柏林-莱比锡倡议。在此框架中，STRESS 将研究漂白事件的代理记录，DIAGENESIS 将研究早期成岩作用期间代理数据的保存潜力。我们将通过制作公共电视纪录片（Arte-TV/ZDF）来确保向更广泛的公众传播我们的研究结果。除了提供对始新世中纬度气候的重要限制之外，我们还将获得对主导当今珊瑚礁（例如滨珊瑚）的类群光增强钙化系统的早期进化阶段的独特见解，以及珊瑚生态系统热应激和地质过去白化的第一个分析证据。这种来自极端气候世界的深度视角将为珊瑚抵抗未来海洋变暖和酸化双重压力的潜在机制提供另一种观点。此外，对珊瑚钙化的深入了解将直接有助于关于中始新世气候最适宜期开始时深海碳酸盐溶解的长期讨论，这是由于全球钙化通量更多地分配到被淹没的大陆架上的珊瑚礁生态系统的结果。