New approaches for understanding group-specific phytoplankton photosynthesis in mixed populations

海洋浮游植物是地球生物地球化学循环的重要组成部分。系统发育多样，为了在复杂和动态的群落中最大限度地利用资源，它们在生理策略上表现出广泛的差异。基于叶绿素荧光的光合效率测量被广泛用于评估浮游植物种群的生理状态，提供了支持种群增长、季节演替和竞争的资源利用的关键信息。光合作用效率通常通过使用荧光测定法（脉冲调幅（PAM）荧光测定法或快速重复率荧光测定法）在“散装”自然种群样本中进行监测。然而，这些方法有一个主要的缺点，即它们不能提供了解混合种群中群落动态所需的物种或群体特定光合作用的信息。这种限制可以通过使用基于显微镜的PAM成像方法来克服，这种方法可以监测单个鉴定细胞的光合效率。然而，这种方法在自然浮游植物种群中受到典型显微镜视野中可以分析的细胞数量（通常是几十个细胞）的严重限制。Mesolens是一种高度复杂的独特显微镜，可产生无像差的宽视场低放大（x4）图像，但具有x40物镜的分辨率和光收集特性，允许同时成像数千个细胞，每个细胞都具有亚细胞分辨率。我们建议对现有的中中生代进行调整，以进行混合自然种群的单细胞PAM成像，为获得前所未有的浮游植物光合性能的物种或群体特定信息提供新的工具。结合一种用于原位生理研究的浓缩活的浮游植物细胞的新方法，我们将为浮游植物的演替和竞争提供更好的机制理解。研究地点包括：1)。西海峡观测站L4每周的新鲜样本将允许详细研究季节演替。2）. 这是一个令人兴奋的机会，将这个设备放置在新投入使用的塔拉国际极地冰站上，该站计划在25年的时间里在北极冬季进行每年的冬季南北北极冰漂移。我们期望这个项目取得的技术发展将在一系列沿海、海洋学和淡水浮游植物研究中得到更广泛的应用。

The marine phytoplankton represent globally important components of the Earth's biogeochemical cycles. Phylogenetically diverse, they exhibit wide variations in physiological strategies in order to maximize resource utilization in complex and dynamic communities. Chlorophyll fluorescence-based photosynthetic efficiency measurements are widely used to assess the physiological status of phytoplankton populations, providing critical information on resource use that underpins population growth, seasonal succession and competition. Photosynthetic efficiency is normally monitored in "bulk" natural population samples by the use of fluorometry (pulse amplitude modulated (PAM) fluorometry or fast repetition rate fluorometry (FRRF)). However these approaches suffer a major drawback in that they do not provide information on species- or group-specific photosynthesis that that is needed to understand community dynamics in mixed populations. Such limitations can be overcome by the use of microscopy-based PAM imaging approaches that can monitor the photosynthetic efficiency of single identified cells. However, this approach is severely limited in natural phytoplankton populations by the number of cells (typically tens of cells) that can be analyzed in a typical microscopic field of view. The Mesolens is a highly sophisticated unique microscope that produces aberration-free wide field low magnification (x4) images but with the resolving power and light collecting properties of a x40 objective, allowing the simultaneous imaging of many thousands of cells, each with sub-cellular resolution. We propose to adapt our existing Mesolens to carry out single cell PAM imaging of mixed natural populations, providing a new tool to gain unprecedented species- or group- specific information on phytoplankton photosynthetic performance. Together with a novel method for concentrating viable phytoplankton cells for in situ physiological studies we will aim to provide better mechanistic understanding of phytoplankton succession and competition. Study sites will include: 1). The Western Channel Observatory station L4 Weekly fresh samples will allow detailed studies of seasonal succession. 2). An exciting opportunity to place this equipment on the newly commissioned Tara International Polar Ice Station that is planned to carry out annual winter north-south Arctic ice drifts through the Arctic winters over a 25 year period. We expect that the technological developments achieved with this project will have far broader application in a range of coastal, oceanographic and freshwater phytoplankton research.