Mechanistic understanding of the role of diatoms in the success of the Arctic Calanus complex and implications for a warmer Arctic

螯虾属的桡足类（以下简称螯虾）是米粒大小的甲壳类动物，是螃蟹和龙虾的远亲，它们分布在整个北冰洋，消耗大量的微小藻类（浮游植物）。这些小动物是许多北极鱼类、海鸟和鲸鱼的主要食物来源。在早春的时候，它们以大量的季节性硅藻为食，硅藻是富含脂肪的浮游植物，在海冰下和开阔的海洋中都有大量繁殖。这使得卡拉努斯能够迅速获得足够的脂肪，在北极冬季食物短缺的几个月里生存下来。硅藻还能产生一种主要的海洋omega-3多不饱和脂肪酸，这是卡拉努斯在冰冻的北极水域成功生存和繁殖所必需的。卡蓝鲸季节性地迁移到更深的水域，以节省能量，减少在越冬过程中被捕食的损失，这一过程被称为滞育，完全由富含碳的脂肪（脂质）提供燃料。这个垂直的“脂质泵”将大量的碳转移到海洋内部，最终代表了大气二氧化碳（CO2）的减少，这是全球碳循环中的一个重要过程。预计整个21世纪持续的全球变暖将对北冰洋硅藻生产力的时间、规模和空间分布产生强烈影响。人们对卡拉努斯岛将如何应对这些变化知之甚少，因此很难理解更广泛的北极生态系统及其生物地球化学将如何受到气候变化的影响。该提案的总体目标是对北极的卡拉努斯将如何受到未来气候变化的影响进行预测性理解。我们将通过五个主要研究领域来实现这一目标：我们将综合北极地区过去的Calanus数据集以及卫星衍生的初级生产数据。这项工作将检验是否更小、更温和的物种已经越来越多地在北极定居。此外，它将考虑生命周期事件的时间在过去几十年中以及不同北极地区之间可能发生的变化。结果数据将用于验证建模工作。我们将进行实地实验，以研究气候驱动的浮游植物数量和omega-3含量的变化如何影响Calanus生命周期的关键特征，包括繁殖和滞育的脂质储存。尖端的技术将研究卡兰纳斯如何以及为什么在没有食物的情况下使用储存的脂肪进行繁殖。获得的新认识将用于制作卡拉努斯生命周期的数值模型，用于未来的预测。该研究项目将开发卡拉努斯的生命周期模型，并模拟北极大片地区目前的分布模式、生命周期事件的时间和储存的脂质（身体状况）的数量。这些预测将与历史数据进行比较。我们将研究Calanus的omega-3脂肪酸含量如何受到食物环境的影响，进而决定其滞育和繁殖成功的模式。不同种类的卡拉努斯的繁殖策略不同，这种方法为预测每个物种将如何受到影响提供了有力的手段，使我们能够在未来各种环境变化的情况下确定赢家和输家。该项目综合将利用该提案之前的所有要素，生成新的卡拉努斯的数值模型，以及食物环境如何影响它们的繁殖策略，从而影响它们在不断变化的北冰洋中的生存能力。这将使我们能够探索未来北冰洋的生产力和生物地球化学将如何变化。这些模型将与英国的地球系统模型相结合，后者直接为了解全球气候变化反馈的国际努力提供信息。

Copepod species of the genus Calanus (Calanus hereafter) are rice grain-sized crustaceans, distant relatives of crabs and lobsters, that occur throughout the Arctic Ocean consuming enormous quantities of microscopic algae (phytoplankton). These tiny animals represent the primary food source for many Arctic fish, seabirds and whales. During early spring they gorge on extensive seasonal blooms of diatoms, fat-rich phytoplankton that proliferate both beneath the sea ice and in the open ocean. This allows Calanus to rapidly obtain sufficient fat to survive during the many months of food scarcity during the Arctic winter. Diatoms also produce one of the main marine omega-3 polyunsaturated fatty acids that Calanus require to successfully survive and reproduce in the frozen Arctic waters. Calanus seasonally migrate into deeper waters to save energy and reduce their losses to predation in an overwintering process called diapause that is fuelled entirely by carbon-rich fat (lipids). This vertical 'lipid pump' transfers vast quantities of carbon into the ocean's interior and ultimately represents the draw-down of atmospheric carbon dioxide (CO2), an important process within the global carbon cycle. Continued global warming throughout the 21st century is expected to exert a strong influence on the timing, magnitude and spatial distribution of diatom productivity in the Arctic Ocean. Little is known about how Calanus will respond to these changes, making it difficult to understand how the wider Arctic ecosystem and its biogeochemistry will be affected by climate change. The overarching goal of this proposal is to develop a predictive understanding of how Calanus in the Arctic will be affected by future climate change. We will achieve this goal through five main areas of research:We will synthesise past datasets of Calanus in the Arctic alongside satellite-derived data on primary production. This undertaking will examine whether smaller, more temperate species have been increasingly colonising of Arctic. Furthermore, it will consider how the timing of life-cycle events may have changed over past decades and between different Arctic regions. The resulting data will be used to validate modelling efforts.We will conduct field based experiments to examine how climate-driven changes in the quantity and omega-3 content of phytoplankton will affect crucial features of the Calanus life-cycle, including reproduction and lipid storage for diapause. Cutting-edge techniques will investigate how and why Calanus use stored fats to reproduce in the absence of food. The new understanding gained will be used to produce numerical models of Calanus' life cycle for future forecasting.The research programme will develop life-cycle models of Calanus and simulate present day distribution patterns, the timing of life-cycle events, and the quantities of stored lipid (body condition), over large areas of the Arctic. These projections will be compared to historical data.We will investigate how the omega-3 fatty acid content of Calanus is affected by the food environment and in turn dictates patterns of their diapause- and reproductive success. Reproductive strategies differ between the different species of Calanus and this approach provides a powerful means by which to predict how each species will be impacted, allowing us to identify the winners and losers under various scenarios of future environmental changes. The project synthesis will draw upon previous all elements of the proposal to generate new numerical models of Calanus and how the food environment influences their reproductive strategy and hence capacity for survival in a changing Arctic Ocean. This will allow us to explore how the productivity and biogeochemistry of the Arctic Ocean will change in the future. These models will be interfaced with the UK's Earth System Model that directly feeds into international efforts to understand global feedbacks to climate change.