Unravelling the fate of coccolithophores (marine microplankton) during times of rapid environmental change

全球气候系统有许多相互作用的组成部分，具有内在的复杂性。理解当前全球变化的最具挑战性的任务之一是对所涉及的组成部分和过程进行梳理和量化。虽然通过将地球主要作为一个物理或化学系统来处理，已经成功地模拟了若干过程，但对生物圈（例如海洋生态系统）的全球变化的定量描述却远远落后。然而，对未来气候变化的任何评估都需要了解自然变异的全部情况。因此，拟议的研究项目旨在从根本上了解环境变化如何影响海洋生态系统，特别是颗石藻，这是单细胞海洋浮游植物的一个主要群体。颗石藻特别令人感兴趣，因为它们在海洋碳循环中发挥着重要作用，既作为初级生产者，又作为影响海洋二氧化碳水平的方解石生产者。据估计，它们贡献了海洋中46%的颗粒有机碳固定，以及约50%的深海碳酸盐生产。然而，目前对快速气候变化如何影响颗石藻的生产、多样性和进化知之甚少。因此，拟议的研究项目旨在确定颗石藻如何受到快速环境变化的影响，如过去200年人为污染（例如二氧化碳水平增加），厄尔尼诺南方涛动（ENSO）和敏感地记录这些快速气候变化的关键地点的季风（例如，加州湾、卡里亚科盆地和阿拉伯海）。特别是，将使用沉积物捕获器和浮游生物样本分析关键物种（如Emiliania huxleyi、Gephyrocapsa oceanica和Florisphaera profunda）的颗石藻通量、组合组成和形态变化对环境变化的响应。所获得的数据将随后被用来重建，以及检查全新世气候变化的影响，每年层积沉积物积累在关键地点的颗石藻。最近开发的最适合于对层状沉积物进行超高分辨率分析的技术和代用品的应用保证了高质量的数据;以这种方式获得的知识对于评估未来全球变化对海洋生态系统的影响至关重要。

The global climate system has many interacting components and is inherently complex. One of the most challenging tasks in understanding current global change is the untangling and quantification of the involved components and processes. While several processes have been successfully modeled by treating the Earth mainly as a physical or chemical system, the quantitative characterization of global change in the biosphere, for example in the marine ecosystem, is lagging far behind. However, any assessment of future climate change requires knowledge of the full range of natural variability. Therefore, the proposed research project is designed towards gaining a fundamental understanding of how environmental change affects the marine ecosystem, especially coccolithophores, a major group of single celled marine phytoplankton. Coccolithophores are of particular interest because they play an important part in the marine carbon cycle both as primary producers and calcite producers that affect the CO2 levels of the ocean. They are estimated to contribute 46% of the particulate organic carbon fixation in the ocean, and about 50% of the deep sea carbonate production. However, little is currently known on how rapid climate variability affects the production, diversity and evolution of coccolithophores. Thus, the proposed research project aims to determine how coccolithophores are affected by rapid environmental changes such as anthropogenic pollution during the last 200 years (e.g. increasing CO2 levels), the El Niño Southern Oscillation (ENSO) and Monsoons from key localities that sensitively record these rapid climate changes (e.g., the Gulf of California, the Cariaco Basin, and the Arabian Sea). In particular, the response of coccolithophores flux, assemblage composition and morphological variations of key species such as Emiliania huxleyi, Gephyrocapsa oceanica and Florisphaera profunda to environmental change will be analysed using sediment trap and plankton samples. The obtained data will be subsequently used to reconstruct as well as examine the impact of climate changes during the Holocene on coccolithophores from annually laminated sediments accumulated at the key localities. The application of recently developed techniques and proxies most suitable for ultra high resolution analysis of laminated sediments guarantees high quality data; the knowledge obtained in this way will be essential in assessing the impact of future global change on the marine ecosystem.