Patterns of reef coral calcification in an upwelling zone (Oman)

上升流区珊瑚礁钙化的模式（阿曼）

• 批准号: 390998412
• 负责人: Professor Dr. Thomas Brachert
• 金额: --
• 依托单位: Abteilung Geologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/390998412?language=en
• 关键词: Patterns; reef; coral; calcification; upwelling

Skeletal calcification of corals in tropical shallow-water coral reefs is increasingly threatened by globally rising sea surface temperatures (SST), lowering of ocean pH, and anthropogenic eutrophication. Except for few culture experiments, the contribution of a single stressor such as high SST, low pH or eutrophy to net calcification of reef corals is not known from the natural environment. The coral reefs of Oman are a natural laboratory to the study of environmental controls on skeletal calcification of future reefs because anthropogenic disturbances are negligible and pronounced spatial gradients of environmental stresses exists between the Arabian Sea upwelling-zone (low SST, low pH) and the Gulf of Oman (high SST, high pH).In an ongoing project funded by the DFG we studied patterns of skeletal calcification of corals (Porites) from Oman. According to our data, corals affected by summer upwelling of the Arabian Sea have diminished skeletal bulk density due to low seawater pH, but enhanced extension rate due to high nutrient availability. On the other hand, corals from the Gulf of Oman have high density because of high aragonite super-saturation and inconspicuous extension. They are protected from bleaching because they benefit during summer from cool-water filaments derived from the upwelling zone. The findings support hypotheses predicting regions of upwelling to represent refuges for coral reefs during future and past warm periods. Important for the success of the project were improvements of the sampling method and calibration of coral-internal age models that allow us for the first time to separate the effects of different (sub-) seasonal stresses on the overall calcification balance. However, delays of the project through unexpected logistical problems with permits by Omani authorities, a laboratory conversion at Mainz University and the general shutdown of laboratory facilities due to the Corona pandemic brought us one year behind schedule. New research questions that came up during the ongoing project and the delays led us to submit a renewal proposal. Within the additional work time, we will complete all planned analytics of the materials already available to us and follow three additional research aims: (1) dating of selected corals (230Th/U) for an even better documentation of high-frequency variations of upwelling, (2) reconstructing the carbonate chemistry of the calcification fluid (B/Ca-δ10B) in order to better understand internal regulation mechanisms vs. external seawater effects on calcification performance, and (3) extracting short cores from massive Porites at an environmental logging station (pH, SST) installed during the project for calibration purposes of proxy data and calcification records.

热带浅水珊瑚礁中珊瑚的骨骼钙化越来越受到全球海洋表面温度（SST）上升，海洋pH值下降和人为富营养化的威胁。除了少数的培养实验，单一的压力，如高SST，低pH值或富营养化的净钙化的礁珊瑚的贡献是未知的从自然环境。阿曼的珊瑚礁是研究环境对未来珊瑚礁骨骼钙化的控制的天然实验室，因为人为干扰可以忽略不计，而且阿拉伯海上升带和上升带之间存在明显的环境应力空间梯度。（低SST，低pH值）和阿曼湾在DFG资助的一个正在进行的项目中，我们研究了阿曼珊瑚（滨珊瑚）骨骼钙化的模式。根据我们的数据，受阿拉伯海夏季上升流影响的珊瑚由于海水pH值低而减少了骨骼体积密度，但由于营养物质的高可用性而提高了扩展速率。另一方面，阿曼湾的珊瑚密度高，因为文石超饱和度高，伸展不明显。它们受到保护，免受漂白，因为它们在夏季受益于来自上升流区的冷水丝。这些发现支持了预测上升流区域在未来和过去温暖时期代表珊瑚礁避难所的假设。对该项目的成功至关重要的是改进了采样方法和校准珊瑚内部年龄模型，使我们能够首次分离不同（亚）季节应力对整体钙化平衡的影响。然而，由于阿曼当局的许可证出现意外的后勤问题，美因茨大学的实验室转换以及Corona大流行病导致实验室设施普遍关闭，项目延迟，使我们比计划晚了一年。在正在进行的项目中出现的新研究问题和延迟导致我们提交了一份更新提案。在额外的工作时间内，我们将完成对现有材料的所有计划分析，并遵循三个额外的研究目标：（1）对选定的珊瑚（230 Th/U）进行测年，以便更好地记录上升流的高频变化，（2）重建钙化流体的碳酸盐化学（B/Ca-δ 10 B），以便更好地了解内部调节机制与外部海水对钙化性能的影响，以及（3）在环境测井站从块状滨珊瑚中提取短岩心（pH，SST），用于校准代理数据和钙化记录。