The evolution of modern marine ecosystems: environmental controls on their structure and function

目前，我们的海洋生态系统受到一系列环境变化的威胁，包括全球气温上升和海洋环流模式的变化。最令人担忧的是，最近的调查显示，海洋的大部分地区正在耗尽氧气，形成了海洋动物无法生存的所谓“死亡区”。随着这些死亡区继续扩大，大量海洋物种可能会灭绝。虽然这些环境变化是当今科学家非常关注的问题，但这并不是海洋生态系统第一次面临这样的威胁。化石记录告诉我们，在过去的许多时候，全球气温上升，海洋环流减缓，缺氧的死亡区在全球海洋中扩大。了解海洋生态系统如何受到过去环境变化的影响，特别是试图找出它们如何应对不断上升的温度和不断减少的氧气，可能有助于我们预测现代生态系统今天将如何应对，以及如何最好地应对当前的危机。现代海洋生态系统经历了数百万年的进化。我们今天看到的在海洋中游泳或生活在海底的动物群体——鱼类、贝类、海胆、海星、珊瑚和浮游生物——大多是在2.5亿年前影响地球生命的最大灭绝事件之后出现的。这一事件消灭了一系列之前成功的动物群体，大多数幸存者都是现代海洋生物的祖先。这次主要的灭绝事件发生在二叠纪晚期，与全球气温上升、海洋环流变化和缺氧死区扩大有关——这些都是当今现代生态系统面临的同样威胁。在晚二叠纪和中生代之后，随着早期现代生态系统的出现和进化，它们受到了一系列类似的环境灾难的打击，全球变暖和死区扩大的组合也很相似。所有这些事件都导致了大范围的灭绝。我们将首次研究全球变暖、海洋环流的变化和缺氧死亡区的扩大对这些早期现代海洋生态系统的影响。我们将首次确定这些生态系统的结构是如何随着时间的推移而变化的，特别是它们在应对不断变化的环境条件时的功能如何。此外，我们将评估海洋生态系统对温度、海洋环流和可用氧变化所带来的灭绝和崩溃的抵抗力是否有所改善。我们将进行这些详细的研究，以首次发现从海底到海洋表面的海洋生态系统的结构和功能如何响应环境变化。为了解决这些问题，我们将在两个不同的尺度上进行一系列相关的研究：(a)海洋生态系统对全球温度和大气二氧化碳和氧气水平长期变化的响应的全球尺度分析；(b)局地尺度、高分辨率分析生态系统对溶解温度、氧浓度和海洋环流等局地环境变化的响应。局部规模的分析将包括对英国、欧洲、美国和北极地区的实地考察，这些地点已知包含我们研究期间四个关键事件的详细记录。全球范围的分析将包括对出版的信息和博物馆收藏的所有已知的存在于中生代的海洋分类群的生态学研究。我们多学科研究的结果将代表我们对温度、海洋环流和溶解氧水平等环境变化对现代海洋生态系统的结构、功能和早期进化的作用的理解发生了一步变化。

Currently, our marine ecosystems are threatened by a number of environmental changes, including rising global temperatures and changes in ocean circulation patterns. Most worryingly of all, recent surveys have shown that large parts of the ocean are running out of oxygen, creating so-called 'dead zones' where no marine animals can live. As these dead zones continue to expand significant numbers of marine species may become extinct. Although these environmental changes are of great concern to scientists today, it is not the first time that marine ecosystems have faced such threats. The fossil record shows us that at many times in the past global temperatures have risen, ocean circulation has slowed down, and oxygen-starved dead zones have expanded throughout the world's oceans. Understanding how marine ecosystems have been affected by past environmental change, and in particular trying to find out how they coped with increasing temperatures and decreasing amounts of oxygen, may help us predict how modern ecosystems will respond today and how best to manage the present crisis. Modern marine ecosystems took millions of years to evolve. The animal groups that we see today swimming in the oceans or living on the seafloor - the fish, shellfish, sea urchins, starfish, corals and plankton - mostly appeared in the aftermath of the biggest extinction event to have affected life on Earth around 250 million years ago. This event wiped out a whole range of previously successful groups of animals, and most of the survivors were the ancestors of modern sea creatures. This major extinction event, which took place in the late Permian period, was associated with rising global temperatures, changes in ocean circulation and expansion of oxygen-poor dead zones - the very same threats facing modern ecosystems today. As early modern-style ecosystems appeared and evolved after the Late Permian and through the Mesozoic, they were struck by a succession of similar environmental catastrophes, with similar combinations of global warming and expanding dead zones. All of these events caused widespread extinction. We will undertake the first study of the effect that global warming, changes in ocean circulation, and expansion of the oxygen-starved dead zones had on these early modern marine ecosystems. We will determine, for the first time, how the structure of these ecosystems changed through time, and in particular how well they functioned, in response to changing environmental conditions. Furthermore, we will evaluate whether there been an improvement in the resistance of marine ecosystems to extinction and collapse brought on by changes in temperature, ocean circulation and available oxygen. We will undertake these detailed studies to discover for the first time how the structure and function of marine ecosystems, from the seafloor to the ocean surface, responded to environmental changes. In order to address these questions, we will undertake a series of linked studies at two contrasting scales: (a) global-scale analyses of marine ecosystem response to long-term changes in global temperature and atmospheric carbon dioxide and oxygen levels; and (b) local-scale, high-resolution analyses of ecosystem response to local environmental changes in dissolved temperature, oxygen concentration, and ocean circulation. Local-scale analyses will involve field expeditions to sites in UK, Europe, America and the Arctic that are known to contain a detailed record through four key events in our study interval. Global-scale analyses will involve ecological study of published information and museum collections of all known marine taxa that existed through the Mesozoic. The results from our multidisciplinary study will represent a step-change in our understanding of the role(s) that environmental changes in temperature, ocean circulation and levels of dissolved oxygen had on the structure, function and early evolution of modern marine ecosystems.