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全球重要组成部分。在系统发育上不同，它们在生理策略上表现出很大的差异，以便在复杂和动态的群落中最大限度地利用资源。基于叶绿素荧光的光合作用效率测量被广泛用于评估浮游植物种群的生理状态，为支持种群增长、季节演替和竞争的资源利用提供关键信息。光合作用效率通常是通过使用荧光法(脉冲调幅(PAM)荧光法或快速重复频率荧光法(FRRF))在“大量”自然种群样本中监测的。然而，这些方法有一个重大缺陷，因为它们没有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。这些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已识别细胞的光合作用效率。然而，这种方法在自然浮游植物种群中受到严重限制，因为在典型的微观视野中可以分析的细胞数量(通常是几十个细胞)。Mesolens是一种高度复杂的独特显微镜，可以产生无像差的广域低放大倍率(X4)图像，但具有x40物镜的分辨率和光收集特性，允许同时对数千个细胞进行成像，每个细胞都具有亚细胞分辨率。我们建议调整我们现有的中层进行混合自然种群的单细胞PAM成像，提供一个新的工具来获得关于浮游植物光合作用性能的前所未有的物种或群体特定信息。结合一种新的方法集中活性浮游植物细胞进行原位生理学研究，我们的目标是提供更好的浮游植物演替和竞争的机制理解。学习地点将包括：1)。西海峡天文台L4每周新鲜样本将允许对季节性演替进行详细研究。2)。将这种设备安装在新投入使用的塔拉国际极地冰站上是一个令人兴奋的机会，该冰站计划在25年内进行每年一次的北极南北冰川漂移。我们预计，该项目取得的技术发展将在一系列沿海、海洋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.