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Quantifying phytoplankton evolution through Cretaceous Oceanic Anoxic Event 2

通过白垩纪海洋缺氧事件 2 量化浮游植物的进化

基本信息

批准号：
NE/G004986/1
负责人：
Paul Bown
金额：
$ 33.25万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FG004986%2F1
关键词：
Quantifying phytoplankton evolution through Cretaceous

项目摘要

The geological record contains fossil shells and shell chemistry that allow us to reconstruct ancient Earth environments. This shows us that Earth has seen a wide range of different climates, including times when it was much colder or warmer than it is now. This research project aims to better understand how life responds to these changing climates by using the geological record of a specific warming event. We are especially interested in finding out what drives biological evolution and how much of a part climate plays in this. It is important to understand how life responds to changing environments, because our modern climate is warming rapidly and we need to find out what the impact of these changes will be. Will we see more extinction? Will life in the oceans become less abundant and so provide less food and absorb less carbon dioxide (which would make climate become warmer even faster)? To answer these questions, we will study a climate-warming event that occurred 93 million years ago, in the Cretaceous, when dinosaurs dominated on land. This greenhouse climate interval saw subtropical forests on Antarctica, crocodile-like animals in the Arctic, no ice-caps and sea-levels that were 70m higher than today. This event is known as Oceanic Anoxic Event 2 (OAE2) because it was first recognised by abundant black shale sediments that indicate that the ocean floors had little or no oxygen, allowing the accumulation of large amounts of carbon from plants and animals. As well as all that carbon burial, this event also saw rapid and extreme climate warming with increases of 6-9C within a few tens of thousands of years. Peak temperatures were at least 36C, compared with modern annual mean temperatures that rarely exceed 30C. So this looks like an ideal event for studying the response of life to warming, but there are some problems. The black shales that occurred during this event do not preserve the fossils that we use to measure evolution. The best fossils for this purpose are the shells of microscopic, single-celled plankton, which are produced in their billions and which are normally preserved in sea-floor sediments, worldwide. However, these shells are made from calcium carbonate and in black shales the shells are usually dissolved away because of acidic fluids in the sediment. To overcome this problem, we have searched the world to find rocks in which the fossils are preserved perfectly. We have found two such places where unusual conditions have preserved plankton fossils of the correct age very well, one in Tanzania (eastern Africa) and one in Morocco (NW Africa). Because these rocks are rich in clay and have never been buried deep in the Earth, the fossils have been protected from damage, and though they are over 90 million years old, they look like modern examples. We will use these fossils to collect information that will tell us how the plankton responded through the OAE2 climate warming. We particularly want to find out whether the rate of evolutionary change increased as the environment changed, and whether more species evolved or became extinct. We will also use these fossils to investigate whether certain types of species were more affected than others. For example, were warm-water-loving species more affected than cool-water types, or were species that produced heavier, thicker shells more affected than types that formed small, delicate shells? By looking at these details of evolution, we can find out which kinds of environmental change were most influential, for example, was it water temperature, food supply, or ocean chemistry (acidification) changes. More broadly, these records of plankton evolution will help us understand how these warm climate events operated and how Earth returned to more normal conditions. With a better understanding of how life responded to these past climate events, we will be better able to make predictions of how Earth's biosphere will respond through the coming decades.

地质记录包含化石贝壳和贝壳化学，使我们能够重建古代地球环境。这向我们表明，地球经历过各种不同的气候，包括比现在更冷或更热的时期。该研究项目旨在通过使用特定变暖事件的地质记录来更好地了解生命如何应对这些变化的气候。我们特别感兴趣的是找出是什么推动了生物进化，以及气候在其中扮演了多大的角色。了解生命如何应对不断变化的环境非常重要，因为我们的现代气候正在迅速变暖，我们需要了解这些变化将产生什么影响。我们会看到更多的灭绝吗？海洋中的生命是否会变得不那么丰富，从而提供更少的食物和吸收更少的二氧化碳（这将使气候变得更快）？为了回答这些问题，我们将研究9300万年前发生在白垩纪的一次气候变暖事件，当时恐龙在陆地上占主导地位。在这段温室气候期间，南极洲有亚热带森林，北极有鳄鱼般的动物，没有冰盖，海平面比今天高出70米。这一事件被称为海洋缺氧事件2（OAE 2），因为它首先被大量的黑色页岩沉积物所识别，这表明海底几乎没有氧气，允许从植物和动物中积累大量的碳。除了所有的碳埋葬，这一事件也见证了快速和极端的气候变暖，在数万年内增加了6- 9摄氏度。峰值温度至少为36摄氏度，而现代年平均温度很少超过30摄氏度。所以这看起来像是研究生命对变暖的反应的理想事件，但也有一些问题。在这一事件中出现的黑色页岩并没有保存我们用来衡量进化的化石。最好的化石是微观的单细胞浮游生物的外壳，它们以数十亿计产生，通常保存在世界各地的海底沉积物中。然而，这些贝壳是由碳酸钙组成的，在黑色页岩中，由于沉积物中的酸性流体，贝壳通常会溶解掉。为了克服这个问题，我们在世界各地寻找化石保存完好的岩石。我们已经发现了两个这样的地方，在那里不寻常的条件下，浮游生物化石的正确年龄保存得很好，一个在坦桑尼亚（东非），一个在摩洛哥（西北非洲）。由于这些岩石富含粘土，而且从未被深埋在地球中，因此这些化石受到了保护，没有受到破坏，尽管它们有9000多万年的历史，但它们看起来像现代的例子。我们将利用这些化石来收集信息，这些信息将告诉我们浮游生物如何通过OAE 2气候变暖做出反应。我们特别想知道进化的速度是否随着环境的变化而增加，以及更多的物种是进化还是灭绝。我们还将利用这些化石来研究某些类型的物种是否比其他物种受到更大的影响。例如，是喜暖水的物种比冷水类型更受影响，还是产生更重，更厚的壳的物种比形成小，精致的壳的类型更受影响？通过观察这些进化的细节，我们可以找出哪些类型的环境变化最具影响力，例如，是水温，食物供应还是海洋化学（酸化）变化。更广泛地说，这些浮游生物进化的记录将帮助我们了解这些温暖的气候事件是如何运作的，以及地球是如何恢复到更正常的状态的。随着对生命如何应对这些过去气候事件的更好理解，我们将能够更好地预测地球生物圈在未来几十年将如何应对。