The pelagic record of ocean acidification since the beginning of industrialisation

地球上的海洋正在吸收人为化石燃料和生物质燃烧释放的相当大一部分二氧化碳。因此，海水的酸碱度正在下降；这一过程被称为海洋酸化。令人担忧的是，这些变化将通过影响栖息地的物种范围以及骨骼和贝壳的钙化，对海洋生物群产生深远的影响。按照目前的二氧化碳吸收速度，海洋表面的平均pH值将低于海洋生物在过去数百万年中的任何时候所经历的pH值。最脆弱的生态系统在极地地区，因此我们将重点放在北大西洋北部。在这里，海水对碳酸盐矿物具有腐蚀性，因此在这些水域中钙化的生物对任何酸化都特别敏感。我们选择了具有代表性的海洋浮游生物群体，它们生活在海洋顶部米的表面(有孔虫和鞭毛虫)，因此生活在自19世纪末工业时期开始以来已经被0.1PH值下降改变的栖息地。有孔虫和球虫是单细胞生物体。我们之所以选择这些群体，是因为它们是1)关键的碳酸盐生产者，因此对全球碳循环做出贡献，以及2)浮游生态系统的重要组成部分。我们如何测试海水的pH值和碳酸盐离子在过去150年中的变化是否影响了具有碳酸盐骨架的生物？科学文献中已经提出了这些钙化剂的变化建议，因此重要的是在同一地点使用更多的物种和不同的生物群来测试这些结果，以评估可能的生态系统影响。该项目将专注于高分辨率沉积物岩心，这将使我们能够以十年分辨率研究海洋浮游生物。我们将能够确定这两个生态系统在过去1000年中的自然变异性，并量化过去150年中的OA变化。我们将对有孔虫和有孔虫进行比较。我们期待着可能的差异，因为前者是浮游动物，在繁殖之前寿命更长，并将海水包裹成钙化。相反，后者是浮游植物，因此钙化和光合作用将受到地表水化学变化的影响，它们每天分开，而不是每两周到每月一次，它们在内部的小泡中钙化。将确定两组动物的钙化变化，确定它们的重量(仅有孔虫)和厚度。随着有孔虫通过增加洞穴而增长，我们可以分析整个生活史，看看大小可能的变化是否与发育时间的变化有关。我们已经使用详细的扫描电子分析和形态计量学，确定了这些变化，不仅针对传统的“地质物种”，而且针对更微妙的“形态类型”，它们已被认为具有特定的环境适应能力，并可能对OA有不同的反应。所有这些工作都将在确定年代的材料的框架内进行，对沉积变化进行分析(筛选)，以确定结果的可比性。环境信息还将有助于解释这些数据。这些结果将确定海洋食物链的基础和全球碳循环的主要贡献者是否已经由于海洋酸化而改变了它们的钙化。需要所有这些信息来改进对海洋生态系统对海洋酸化的脆弱性、它们有多大可能适应和支持向海洋生物资源政策制定者和管理人员提供关于海洋酸化对海洋生态系统的风险的可能大小和时间尺度的有效建议的预测。

The planet's oceans are absorbing a substantial fraction of the CO2 released by anthropogenic fossil fuel and biomass burning. As a consequence the pH of seawater is dropping; a process called ocean acidification. The concern is that these changes will have a profound impact on marine biota by affecting both species range of habitat and the calcification of their skeletons and shells. At the current rate of CO2 uptake, the average surface ocean pH will be lower than that experienced by marine organisms at any time over the last several million years. The most vulnerable ecosystems are in the polar regions and hence we will focus on the northern North Atlantic. Here seawater is corrosive to carbonate minerals and so organisms that calcify in these waters will be particularly sensitive to any acidification. We have selected representative groups of marine plankton that live at the surface in the top metres of the ocean (foraminifers and coccolithophores) and hence in habitats already altered by the 0.1 pH drop since the start of the industrial period in the late 19th Century. Foraminifers and coccolithophores are single-celled organisms. We have selected these groups because they are 1) key carbonate producers and hence contribute to global carbon cycle, and 2) significant components of the planktic ecosystem. How can we test if the seawater pH and carbonate ion changes over the last 150 years have influenced organisms with carbonate skeletons? Changes have already been suggested in the scientific literature for these calcifiers and so it is important to test these results using a larger number of species and different groups of organisms at the same location to assess possible ecosystem impacts. The project will focus on high resolution sediment cores which will allow us to study marine plankton at decadal resolution. We will be able to determine both, natural variability within these ecosystems over the last 1000 years and quantify OA changes over the last 150 years. We will compare and contrast foraminifers and coccolithophores. We are expecting possible differences as the former are zooplankton, live much longer before reproducing and encapsulate sea water to calcify. The contrast, the latter are phytoplankton and hence calcification and photosynthesis will be influenced by the changes in surface water chemistry, they divide daily instead of bi-weekly to monthly and they calcify in an internal vesicle. Changes in calcification will be determined for both groups, determining their weight (just foraminifers) and thickness. As foraminifers grow by adding chambers, we can analyse the entire life history and see if possible changes in size are related to changes in timing of development. We has, using detailed scanning electron analysis and morphometics, determine these changes not just for the traditional 'geological species' but for more subtle 'morphotypes' which have been recognised to have specific environmental adaptation and potentially different reactions to OA. All of this work will be done in a framework of well dated material, analysed for sedimentological alterations (winnowing) to ascertain the comparability of the results. Environmental information will additionally help to interpret the data. These results will determine if the base of the marine food chain and the major contributors to the global carbon cycle, have already altered their calcification due to ocean acidification. All this information is needed to improve predictions of how vulnerable marine ecosystems are to ocean acidification, how likely they are able to adapt and support effective advice to policy makers and managers of marine bioresources on the possible size and timescale of risks of ocean acidification to marine ecosystems.