Fish like it hot? Response of fish and shark communities to abrupt past global warming

5600万年前的古新世-始新世热盛期（PETM）是新生代一系列全球变暖事件中规模最大的一次。在这一事件中，海洋迅速升温超过5摄氏度，变得更加酸性，世界变得更加潮湿和多风暴，对陆地和海洋中的生命产生了深远的影响。PETM是由同位素轻碳（可能来自火山活动）注入大气驱动的，许多相关的环境变化与今天发生的相似。因此，PETM通常被认为是理解人类环境变化及其影响的最佳地质模拟。然而，虽然大量的研究已经调查了PETM生物和环境变化，很少有调查的反应和对海洋脊椎动物的长期影响。这至少部分是因为身体化石记录是不完整的，因为缺乏合适的沉积物和对可用序列的年龄控制非常差，以评估短期生物反应。然而，解决顶级营养消费者对现代人为变化的反应和恢复力是至关重要的，因为预测在未来世纪热带社区的生产力，多样性和身体大小的显着减少，对许多海洋生态系统和依赖这些资源的人口的关键影响。幸运的是，鱼化石（=鱼牙齿和鲨鱼的牙齿，一般小于1毫米的大小）是普遍存在于海洋沉积物中，是一个未得到充分利用，但强大的资源，产生相对连续和高度时空分辨率的记录鱼类和鲨鱼群落随着时间的推移。学生将利用这一新颖的档案汇编现有的记录，并在全球范围内的PETM鱼类和鲨鱼群落的生产力和多样性的变化产生多个新的记录。这些数据将与广泛的古环境数据集相结合。将解决的关键问题包括：-鲨鱼和鱼类群落如何在PETM期间发生变化？- 高纬度和低纬度地区的反应相似吗？温度是鱼类和鲨鱼群落变化的主要驱动力吗？突发性气候事件在塑造鱼类和鲨鱼进化中扮演什么角色？

The Palaeocene-Eocene Thermal Maximum (PETM) ~56 million years ago, is the largest of a series of abrupt Cenozoic global warming events. During this event, the oceans rapidly warmed by >5 degrees C and became more acidic, and the world became wetter and stormier with profound consequences for life on land and in the oceans. The PETM was driven by the injection of isotopically light carbon (likely from volcanism) into the atmosphere, and many of the associated environmental changes are similar to those occurring today. Therefore, the PETM is often considered the best geological analogue to understand anthropogenic environmental change and its impacts. However, whilst a large number of studies have investigated PETM biotic and environmental change, very few have investigated the response and long-term impact on marine vertebrates. This is, at least in part, because the body fossil record is patchy, because of a lack of suitable sediments and very poor age control on available sequences to assess short-term biological responses. Yet, resolving the response and resilience of top level trophic consumers to modern anthropogenic change is of vital importance because of predictions of significant reductions in tropical communities productivity, diversity and body size over the coming century with critical implications for many marine-ecosystems and human populations dependent on these resources. Fortunately, ichthyoliths (= fish teeth and shark denticles, generally <1 mm in size) are pervasive in marine sediments and are an underutilized but powerful resource for generating relatively continuous and highly temporally and spatially resolved records of fish and shark communities through time. The student will utilise this novel archive to compile existing records and generate multiple new records of changes in the productivity and diversity of fish and shark communities across the PETM globally. These data will be integrated with extensive palaeoenvironmental datasets. Key questions that will be addressed include: - How did shark and fish communities change across the PETM? - Did high vs low latitude communities respond similarly?- Was temperature the dominant driver of change in fish and shark communities?- What role do abrupt climate events play in shaping fish and shark evolution?