Diatom Autecological Responses with Changes To Ice Cover (Diatom-ARCTIC)

近几十年来，随着全球变暖的极地放大，我们目睹了北极海冰的覆盖范围和季节性发生了前所未有的变化，北冰洋内淡水储量增加，远洋初级生产者对养分的需求也随着开放海洋年持续时间的增加而增加。这些过程有可能改变北极海冰藻华的物候、物种组成、生产力和营养价值，对海洋系统的营养功能和碳循环具有深远的影响。随着北极环境条件的不断变化，冰藻的栖息地将越来越受到破坏。冰藻华主要是硅藻，为水生食草动物提供了集中的食物来源，而浮游植物在水柱中的生长是有限的，可以贡献北极海洋年初级产量的一半。传统上，冰藻是作为一个单一的群落来研究的，不区分单个物种。然而，物种的组成在不同地区之间和整个春季的过程中可能会有很大的差异，这是当地环境强迫的一个功能。因此，目前估算北极海洋生产力和预测气候变暖对冰藻群落影响的方法可能是不准确的，因为它们忽略了海冰藻类对变化的冰生境条件的生态（物种特异性）反应。北极硅藻将标志着北极海冰藻类及其生产研究的新篇章。我们的项目超越了其他项目，将群落组成的实地观察结果和针对单一物种的创新实验室实验结果直接整合到预测性生物地球化学模型中。在现场采样期间，使用遥控车辆为我们提供了一个独特的机会来研究自然海冰中藻类物种形成的时空环境控制。北极硅藻野外观测将指导实验室实验，以确定单个硅藻物种在一系列关键生长条件下的光生理反应：光、盐度和养分有效性。额外的实验将表征藻类脂质组成作为生长条件的函数-量化食物资源质量作为物种组成的函数。此外，新的分析工具，如气相色谱-质谱和化合物特异性同位素分析将结合起来，以更好地分类冰藻类中存在的脂质类型。然后，现场和实验室结果将被纳入最先进的BFM-SI冰藻生物地球化学模型，以便根据直接观察到的生态反应准确模拟海冰的总产量和净产量。该模型将用于描述当代北极地区不同海冰生长栖息地的藻类生产力。通过将未来气候情景应用于该模型，我们还将预测未来几十年海冰栖息地在不断演变的北极发生变化时的冰藻生产力。我们的项目针对的是CAO项目第一阶段的一个主要研究缺口：海冰栖息地对北冰洋生态系统结构和生物地球化学功能的具体贡献。为此，硅藻北极将北极奖和DIAPOD的活动结合在一起，并将其联系起来，同时进一步建立英国和德国合作伙伴之间的新合作，为2019/20年的马赛克运动做准备。

Following the polar amplification of global warming in recent decades, we have witnessed unprecedented changes in the coverage and seasonality of Arctic sea ice, enhanced freshwater storage within the Arctic seas, and greater nutrient demand from pelagic primary producers as the annual duration of open-ocean increases. These processes have the potential to change the phenology, species composition, productivity, and nutritional value of Arctic sea ice algal blooms, with far-reaching implications for trophic functioning and carbon cycling in the marine system. As the environmental conditions of the Arctic continue to change, the habitat for ice algae will become increasingly disrupted. Ice algal blooms, which are predominantly species of diatom, provide a concentrated food source for aquatic grazers while phytoplankton growth in the water column is limited, and can contribute up to half of annual Arctic marine primary production. Conventionally ice algae have been studied as a single community, without discriminating between individual species. However, the composition of species can vary widely between regions, and over the course of the spring, as a function of local environmental forcing. Consequently, current approaches for estimating Arctic-wide marine productivity and predicting the impact of climate warming on ice algal communities are likely inaccurate because they overlook the autecological (species-specific) responses of sea ice algae to changing ice habitat conditions. Diatom-ARCTIC will mark a new chapter in the study of sea ice algae and their production in the Arctic. Our project goes beyond others by integrating the results derived from field observations of community composition, and innovative laboratory experiments targeted at single-species of ice algae, directly into a predictive biogeochemical model. The use of a Remotely-Operated Vehicle during in situ field sampling gives us a unique opportunity to examine the spatio-temporal environmental controls on algal speciation in natural sea ice. Diatom-ARCTIC field observations will steer laboratory experiments to identify photophysiological responses of individual diatom species over a range of key growth conditions: light, salinity and nutrient availability. Additional experiments will characterise algal lipid composition as a function of growth conditions - quantifying food resource quality as a function of species composition. Furthermore, novel analytical tools, such as gas chromatography mass spectrometry and compound specific isotope analysis will be combined to better catalogue the types of lipid present in ice algae. Field and laboratory results will then be incorporated into the state-of-the-art BFM-SI biogeochemical model for ice algae, to enable accurate simulations of gross and net production in sea ice based on directly observed autecological responses. The model will be used to characterise algal productivity in different sea ice growth habitats present in the contemporary Arctic. By applying future climate scenarios to the model, we will also forecast ice algal productivity over the coming decades as sea ice habitats transform in an evolving Arctic. Our project targets a major research gap in Phase I of the CAO programme: the specific contribution of sea ice habitats to ecosystem structure and biogeochemical functioning within the Arctic Ocean. In doing so, Diatom-ARCTIC brings together and links the activities of ARCTIC-Prize and DIAPOD, while further building new collaborations between UK and German partners leading up to the 2019/20 MOSAiC campaign.