Impacts of global warming in sentinel systems: from genes to ecosystems

气候变化，特别是气候变暖对自然生态系统的影响仍然知之甚少，迄今为止的研究主要集中在个别物种上(例如北极熊的活动范围转移)。然而，多物种系统(食物网、生态系统)可以具有紧急特性，这些特性只能从系统层面来理解。在给定的食物网络中，微生物世界是驱动关键生态系统过程、生物地球化学循环(例如碳循环)和网络属性的引擎，但由于难以识别哪些微生物存在以及它们在做什么，微生物世界一直隐藏在人们的视线之外。最近的下一代测序革命已经消除了这一瓶颈，我们现在可以打开微生物“黑匣子”来表征元基因组(“谁在那里？”)和metatranscritome(“他们在做什么？”)第一次成为社区的一员。这些进展将使我们能够解决一个关键的首要问题：我们应该期待全球对全球变暖的反应吗？有许多理论认为情况可能是这样，包括生态学的“新陈代谢理论”和全球微生物生物地理学的“无所不在”假说，然而，这些理论还没有在适当的规模和适当的实验环境中得到严格的测试，使我们能够在真实的多物种系统中确定模式和因果关系。我们将使用5个高纬度地区(斯瓦尔巴群岛、冰岛、格陵兰、阿拉斯加、堪察加)地热变暖的淡水，评估从基因到食物网和整个生态系统等多种生物组织的变暖影响，这些地区的变暖预计特别迅速。我们的研究将首次以前所未有的规模描述气候变化对多物种系统的影响。对这些“哨兵系统”的调查将辅之以在这些实地进行的建模和实验，以及在实地的100个大型“中间生态系统”(人工溪流和池塘)以及实验室中由机器人组装的1,000个微生物群落的“微观世界”。我们新的基因到生态系统的方法将使我们能够整合生物多样性和生态系统功能的衡量标准。例如，我们将量化关键的功能基因，以及除了测量生态系统功能(例如，与碳循环相关的过程)外，还将量化哪些基因被开启(“后转录组”)。我们还将测量气候变化对我们在自然界中发现的相互作用的物种的复杂网络的影响-达尔文将其称为“纠缠的银行”-因为食物网和其他类型的网络可能会产生违反直觉的反应，而孤立地研究物种是无法预测的。一个总的目标是评估“生物多样性保险”的范围和自然系统面对气候变化的复原力。我们将把我们的洲际调查与自然实验、生物测定、操纵和数学模型相结合来完成这项工作。例如，我们将描述温度介导的生物多样性损失如何危及基因库和整个生态系统的关键功能属性。在学术文献和政策中有一种假设，即淡水生态系统相对具有弹性，因为表面上巨大的功能冗余空间可以补偿面对气候变化时的物种损失。然而，这在自然系统中还没有得到经验上的量化，在估计功能冗余程度方面的错误可能会产生重大的环境和经济影响。这项研究将解决我们的5个主题工作包中的一组关键的具体问题和假设，对纯生态和应用生态都具有广泛的意义，这些问题和假设的结合也提供了比以往任何时候都更全面的视角。

The impacts of climate change, and warming in particular, on natural ecosystems remain poorly understood, and research to date has focused on individual species (e.g. range shifts of polar bears). Multispecies systems (food webs, ecosystems), however, can possess emergent properties that can only be understood using a system-level perspective. Within a given food web, the microbial world is the engine that drives key ecosystem processes, biogeochemical cycles (e.g. the carbon-cycle) and network properties, but has been hidden from view due to difficulties with identifying which microbes are present and what they are doing. The recent revolution in Next Generation Sequencing has removed this bottleneck and we can now open the microbial "black box" to characterise the metagenome ("who is there?") and metatranscriptome ("what are they doing?") of the community for the first time. These advances will allow us to address a key overarching question: should we expect a global response to global warming? There are bodies of theory that suggest this might be the case, including the "Metabolic Theory of Ecology" and the "Everything is Everywhere" hypothesis of global microbial biogeography, yet these ideas have yet to be tested rigorously at appropriate scales and in appropriate experimental contexts that allow us to identify patterns and causal relationships in real multispecies systems. We will assess the impacts of warming across multiple levels of biological organisation, from genes to food webs and whole ecosystems, using geothermally warmed freshwaters in 5 high-latitude regions (Svalbard, Iceland, Greenland, Alaska, Kamchatka), where warming is predicted to be especially rapid,. Our study will be the first to characterise the impacts of climate change on multispecies systems at such an unprecedented scale. Surveys of these "sentinel systems" will be complemented with modelling and experiments conducted in these field sites, as well as in 100s of large-scale "mesocosms" (artificial streams and ponds) in the field and 1,000s of "microcosms" of robotically-assembled microbial communities in the laboratory. Our novel genes-to-ecosystems approach will allow us to integrate measures of biodiversity and ecosystem functioning. For instance, we will quantify key functional genes as well as quantifying which genes are switched on (the "metatranscriptome") in addition to measuring ecosystem functioning (e.g. processes related to the carbon cycle). We will also measure the impacts of climate change on the complex networks of interacting species we find in nature - what Darwin called "the entangled bank" - because food webs and other types of networks can produce counterintuitive responses that cannot be predicted from studying species in isolation. One general objective is to assess the scope for "biodiversity insurance" and resilience of natural systems in the face of climate change. We will combine our intercontinental surveys with natural experiments, bioassays, manipulations and mathematical models to do this. For instance, we will characterise how temperature-mediated losses to biodiversity can compromise key functional attributes of the gene pool and of the ecosystem as a whole. There is an assumption in the academic literature and in policy that freshwater ecosystems are relatively resilient because the apparently huge scope for functional redundancy could allow for compensation for species loss in the face of climate change. However, this has not been quantified empirically in natural systems, and errors in estimating the magnitude of functional redundancy could have substantial environmental and economic repercussions. The research will address a set of key specific questions and hypotheses within our 5 themed Workpackages, of broad significance to both pure and applied ecology, and which also combine to provide a more holistic perspective than has ever been attempted previously.