Ecological response to environmental change in the Boreal Realm and the origins of three mass extinction events

自从大约5.4亿年前地球上的寒武纪生命大爆发以来，生态系统遭受了反复的大灭绝。从那以后，至少发生了五次大灭绝，最近一次是著名的65Ma事件，那次事件使恐龙灭绝。生命已经显示出了惊人的适应性，因此，严重的环境压力导致了大规模的物种灭绝。我们生活在这样一个时代，人们越来越担心地球即将看到，或者已经在经历一场与地质历史上的大灭绝相媲美的现代大灭绝。2011年6月，国际自然保护联盟（IUCN）报告称，海洋环境压力的组合正在创造与之前每次大灭绝相关的条件。最大的威胁是气候变暖（主要来自温室气体）、海洋缺氧、海洋酸化和富营养化（这一过程会导致生物大量繁殖，但最终会破坏生态系统的稳定）。过去和现在这些威胁的不同之处在于，今天它们有人类的起源。在过去，它们可能是由灾难性的火山作用造成的，广泛分布的火山岩（被称为“大火成岩省”）与大多数物种灭绝有关。过去和现在变化的根本原因可能不同，但令人担忧的是，结果（灭绝）可能是相同的。我们可以从地球的过去中学到很多东西，并且可以在未来的情景和地质记录中的大规模灭绝之间找到相似之处。上述所有的环境压力都被认为是二叠纪末期（251Ma）有史以来最大的危机的原因，当时95%的物种消失了。类似的环境变化也与早期的中二叠世（260Ma）灭绝和随后的三叠纪末期（200Ma）的另一次灭绝有关。这6000万年的时间间隔见证了地球历史上一些最重要、最引人注目的事件，每一次灭绝都从根本上塑造了进化，从而塑造了我们的存在。在这个项目中，我将研究260-200Ma之间的三个事件中的每一个，特别关注北极海洋，一个被称为“北方王国”的地区。不仅人们对北方地区过去的物种灭绝知之甚少，这个地区未来的不确定性也很大。我的调查将从斯匹次卑尔根和西伯利亚的地质野外工作开始，这两个地区在二叠纪和三叠纪时期都位于北极。我将对三个灭绝间隔进行采样，我的第一个目标是计算出灭绝的时间和严重程度，以及哪些物种受到的影响最大。我将使用我的样品的显微镜载玻片来做这个。我将使用几种技术来评估哪些环境压力可能是造成这些危机的原因。这些技术包括钼和锶同位素的地球化学分析，在高倍显微镜下观察微小的黄铁矿斑点，以及使用一个非常强大的计算机模型，称为GENIE，所有这些都告诉我们过去的海洋。一个主要的挑战是将极地地区的岩石与热带地区的岩石联系起来，以便弄清楚极地海洋受到的影响是多还是少。我将根据岩石中的碳同位素制作一个“化学时钟”，这将使我能够将斯匹次卑尔根岛和俄罗斯的序列与其他地方的序列相匹配。该项目的主要目标是确定灭绝风险是否存在纬度变化。这可能会影响未来北方群落的命运，我的研究将为未来世界海洋的治理提供信息，因为我们希望防止当代的大规模灭绝。研究结果不仅对地质学家有用，而且对政策制定者也有帮助，这些政策制定者从世界自然保护联盟（IUCN）一直到联合国（un），最终的任务是为子孙后代保护我们的海洋。

Since the Cambrian Explosion of life on Earth, about 540 million years ago (Ma), ecosystems have been suffered repeated mass extinctions. There have been at least five major extinctions since then, most recently the famous event 65Ma, that wiped out the dinosaurs. Life has shown itself to be remarkably resilient, and it follows that mass extinctions result from serious environmental stress. We live in a time of growing concern that Earth is about to see, or already is going through, a modern mass extinction to rival those of the geological past. In June 2011, the International Union for Conservation of Nature (IUCN) reported that a combination of environmental stresses on the oceans is creating the conditions associated with every previous mass extinction. The greatest threats are warming (mainly from greenhouse gases), marine oxygen depletion, ocean acidification, and eutrophication (a process that leads to blooms in life but can ultimately destabilise ecosystems). The difference between these threats in the past and present is that today they have a human origin. In the past they may have resulted from catastrophic volcanism, with widespread volcanic rocks (known as "large igneous provinces") associated with most extinctions. The underlying cause of change may be different between past and present, but there is concern that the effect (extinction) may be the same. We can learn much from Earth's past, and parallels can be drawn between future scenarios, and mass extinctions in the geological record. All of the aforementioned environmental stresses have been suggested as causes of the biggest crisis of all time, at the close of the Permian (251Ma), when 95% of species disappeared. Similar environmental changes have also been implicated in an earlier extinction in the Middle Permian (260Ma), and another at the end of the subsequent Triassic period (200Ma). This 60 million year interval witnessed some of the most important and remarkable events in the history of the planet, each extinction fundamentally shaping evolution and therefore our very existence.In this project I will study each of the three events between 260-200Ma, paying particular attention to Polar north oceans, an area known as the "Boreal Realm". Not only are past extinctions poorly understood in the Boreal Realm, this region has greatest uncertainty in the future. My investigations will start with geological fieldwork in Spitsbergen and Siberia, both regions that in the Permian and Triassic, as now, were located in the Arctic. I will sample the three extinction intervals, and my first objective will be to work out when, and how severe the extinctions were, and which species were most affected. I will do this using microscope slides of my samples. I will use several techniques to evaluate which environmental stresses were the likely causes of these crises. These techniques include geochemical analyses of molybdenum and strontium isotopes, looking at tiny pyrite blobs under a high-power microscope, and using an extremely powerful computer model, known as GENIE, all of which tell us about past oceans. A major challenge is to correlate rocks from the Polar regions with those from the tropics, in order to work out whether the Polar oceans suffered more, or less. I will produce a "chemical clock" based on carbon isotopes in the rocks, which will allow me to match sequences in Spitsbergen and Russia with those from elsewhere.The main goal of this project is to identify whether there is a latitudinal variation to extinction risk. This might influence the fate of Boreal communities in the future, and my study will inform future governance of the world's oceans, as we look to prevent a contemporary mass extinction. The results will not only be useful for geologists, but also to policy makers that extend through groups such as IUCN, right up to the United Nations, that is ultimately charged with protecting our oceans for future generations.