Ocean carbon cycling since the middle Miocene: testing the metabolic hypothesis

中新世中期以来的海洋碳循环：检验代谢假说

• 批准号: NE/N001621/1
• 负责人: Paul Pearson
• 金额: $ 76.59万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN001621%2F1
• 关键词: Ocean; carbon; cycling; since; middle

Respiration - the process by which organic matter (food) is broken down to provide energy, releasing carbon dioxide - is strongly temperature-dependent. For every ten degrees increase in temperature, it occurs about 2 and a half times faster. We are respiring organisms but we don't notice this because our body temperatures are regulated, but cold-blooded creatures do, and so too do the most important respirers of all in terms of global processes - the bacteria and other microbes. This is why we put food in the fridge, and why a tropical swamp is a much more biologically active place than a temperate bog. Recently there has been a dawning realization among Earth System scientists that this marked temperature-dependency of microbial metabolism must be taken into account if we are to understand some of the big global feedbacks involved in climate change, and hence we should incorporate it into Earth System computer models.One important process that helps regulate the amount of CO2 in the atmosphere occurs in the ocean, and is called the 'biological pump'. Algae photosynthesize in the photic zone at the surface, forming the base of the food chain. Most of this organic matter gets eaten up and respired in the surface layer and the CO2 is returned to the atmosphere, but a substantial proportion sinks to deeper water. Most of it does, eventually, also get broken down by bacteria, but here the CO2 released is isolated from the surface. Some of the organic matter can reach the sea floor where it can be incorporated into sediments, forming the hydrocarbon source rocks of the future. The rain of organic matter sinking to the deep sea and sediments produces a compensatory 'pump' of CO2 from the atmosphere to the ocean. Now imagine we turn up the temperature in the water column as a result of climate change. This is good news for the bacteria which use up the sinking organic matter more efficiently. Less carbon gets removed from the surface ocean hence CO2 accumulates in the atmosphere until a new balance is restored. Because CO2 is an important greenhouse gas, contributing to global warming when it is in the atmosphere, this process could theoretically accentuate the warming process, or work the other way round on a cooling planet. It is important that we understand how important this feedback is in the real world, and what knock-on effects it may have in other parts of the Earth System. We have devised a way of studying it in the Earth's past, using fossil sediments from the sea floor. We plan to take a series of sediment samples spanning the last 15 million years across the oceans to investigate the efficiency of the biological pump. The planet has cooled markedly over this period so we predict major changes to the functioning of ocean ecosystems and the biological pump. We will study the chemical composition of fossil shells of foraminifera (microscopic protists that occur in large numbers) that lived distributed through the water column. By using a combination of geochemical techniques we can establish the temperature profile, pH profile, and strength of the biological pump.To explore the data we will use a specially modified version of a state-of-the-art Earth System Model that will take into account temperature-dependency of metabolic processes. We will then use the model to investigate its impact on a range of globally important factors such as patterns of organic carbon burial and atmospheric carbon dioxide, and investigate how important these factors are for future climate change.We predict that global cooling over the last 15 million years has produced improved oxygenation and food supply in deep planktonic niches (the so-called 'twilight zone' of the ocean) and that this would have spurred evolutionary innovation at depth. We will test this idea by studying plankton abundance patterns at depth in time and space and investigating whether there has been enhanced evolution in this environment.

呼吸 - 分解有机物（食物）以提供能量并释放二氧化碳的过程 - 强烈依赖温度。对于温度的每10度升高，它发生的速度约为2秒半。我们正在呼吸生物，但我们不会注意到这一点，因为我们的体温受到调节，但是冷血的生物也可以，因此在全球过程中最重要的呼吸器也是如此 - 细菌和其他微生物。这就是为什么我们将食物放在冰箱中，以及为什么热带沼泽比温带沼泽更为活跃的地方。最近，地球系统科学家之间已经有一个意识到，如果我们要理解一些在气候变化中涉及的一些大全球反馈，那么必须考虑微生物代谢的明显温度依赖性，因此我们应该将其纳入地球系统计算机模型中。一种重要的过程，有助于调节海洋和泵的大气中的二氧化碳量。藻类光合作用在表面的光区域中，形成了食物链的底部。这种有机物的大部分在表面层被吞噬并呼吸，并且二氧化碳被返回到大气中，但很大一部分落在更深的水中。最终，其中大多数也会被细菌分解，但是在这里释放的二氧化碳是从表面隔离的。一些有机物可以到达可以将其掺入沉积物中的海底，从而形成未来的碳氢化合物岩石。有机物的雨水下沉到深海和沉积物中，从大气到海洋产生了二氧化碳的补偿性“泵”。现在，想象一下，由于气候变化，我们在水柱中的温度调高。对于细菌而言，这是一个好消息，这些细菌更有效地消耗了下沉的有机物。从表面海洋中除去碳较少，因此二氧化碳积累在大气中，直到恢复新的平衡为止。由于二氧化碳是重要的温室气体，在大气中有助于全球变暖，因此从理论上讲，这一过程可以突出变暖过程，或者以相反的方式在冷却星球上进行工作。重要的是，我们必须了解这种反馈在现实世界中的重要性，以及它在地球系统其他地区可能产生的敲门效应。我们已经设计了一种在地球地板上使用化石沉积物在地球过去研究它的方法。我们计划采用一系列跨越海洋的沉积物样品，以研究生物泵的效率。在此期间，地球已经明显冷却，因此我们预测海洋生态系统和生物泵功能的重大变化。我们将研究通过水柱分布的有孔虫（大量发生的微观生物）的化石壳的化学组成。通过使用地球化学技术的组合，我们可以建立生物泵的温度曲线，pH值和强度。探索数据，我们将使用特殊修改的最先进的地球系统模型的版本，该版本将考​​虑代谢过程的温度依赖性。 We will then use the model to investigate its impact on a range of globally important factors such as patterns of organic carbon burial and atmospheric carbon dioxide, and investigate how important these factors are for future climate change.We predict that global cooling over the last 15 million years has produced improved oxygenation and food supply in deep planktonic niches (the so-called 'twilight zone' of the ocean) and that this would have spurred evolutionary innovation at 深度。我们将通过研究时间和空间深度的浮游生物丰度模式来测试这一想法，并研究在这种环境下是否有增强的演变。

项目成果

Temperature dependency of metabolic rates in the upper ocean: A positive feedback to global climate change?

• DOI: 10.1016/j.gloplacha.2018.08.017
• 发表时间: 2018-11-01
• 期刊: GLOBAL AND PLANETARY CHANGE
• 影响因子: 3.9
• 作者: Boscolo-Galazzo, F.;Crichton, K. A.;Pearson, P. N.
• 通讯作者: Pearson, P. N.

Future-proofing the Cenozoic macroperforate planktonic foraminifera phylogeny of Aze & others (2011).

• DOI: 10.1371/journal.pone.0204625
• 发表时间: 2018
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Fordham BG;Aze T;Haller C;Zehady AK;Pearson PN;Ogg JG;Wade BS
• 通讯作者: Wade BS

Late Neogene evolution of modern deep-dwelling plankton

现代深栖浮游生物的新近纪晚期演化

• DOI: 10.5194/bg-2021-230
• 发表时间: 2021
• 作者: Boscolo-Galazzo F

Calibration of key temperature-dependent ocean microbial processes in the cGENIE.muffin Earth system model

• DOI: 10.5194/gmd-2019-344
• 发表时间: 2020-02
• 期刊: Geoscientific Model Development Discussions
• 作者: K. Crichton;Jamie D. Wilson;A. Ridgwell;P. Pearson

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

• DOI: 10.5194/cp-17-2223-2021
• 发表时间: 2021-10-21
• 期刊: CLIMATE OF THE PAST
• 影响因子: 4.3
• 作者: Crichton, Katherine A.;Ridgwell, Andy;Pearson, Paul N.
• 通讯作者: Pearson, Paul N.