The pelagic record of ocean acidification since the beginning of industrialisation

地球上的海洋正在吸收大量由人为化石燃料和生物质燃烧释放的二氧化碳。因此，海水的pH值正在下降；这个过程被称为海洋酸化。令人担忧的是，这些变化将通过影响物种的栖息地范围和骨骼和外壳的钙化，对海洋生物群产生深远的影响。按照目前二氧化碳吸收的速度，海洋表面的平均pH值将低于海洋生物在过去几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，因此我们将重点关注北大西洋北部。这里的海水对碳酸盐矿物具有腐蚀性，因此在这些海水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几米的表面（有孔虫和球石藻），因此，自19世纪末工业时期开始以来，pH值下降0.1已经改变了它们的栖息地。有孔虫和球石藻是单细胞生物。我们之所以选择这些群落，是因为它们是1)主要的碳酸盐生产者，因此对全球碳循环做出了贡献；2)浮游生态系统的重要组成部分。我们如何测试海水pH值和碳酸盐离子在过去150年的变化是否影响了碳酸盐骨架的生物？科学文献中已经提出了这些钙化剂的变化，因此，在同一地点使用更多的物种和不同的生物群体来测试这些结果，以评估可能的生态系统影响，这一点很重要。该项目将侧重于高分辨率沉积物岩心，这将使我们能够以年代际分辨率研究海洋浮游生物。我们将能够确定过去1000年这些生态系统内的自然变率，并量化过去150年的OA变化。我们将比较和对比有孔虫和球石藻。我们期待可能的差异，因为前者是浮游动物，在繁殖之前寿命更长，并将海水封装以钙化。相比之下，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，它们每天分裂，而不是每两周或每月，它们在内部囊泡中钙化。钙化的变化将决定两组，决定它们的重量（只是有孔虫）和厚度。当有孔虫通过增加腔体而成长时，我们可以分析整个生活史，看看可能的大小变化是否与发育时间的变化有关。我们使用详细的扫描电子分析和形态学，不仅确定了传统的“地质物种”的这些变化，还确定了更微妙的“形态”，这些“形态”已被认为具有特定的环境适应性和对OA的潜在不同反应。所有这些工作都将在年代确定的材料框架内完成，分析沉积学变化（筛选），以确定结果的可比性。环境信息也将有助于解释数据。这些结果将决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有多脆弱的预测，它们适应海洋酸化的可能性有多大，并就海洋酸化对海洋生态系统可能造成的风险的规模和时间尺度向政策制定者和海洋生物资源管理者提供有效建议。

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.