Quantifying Synergies between Multiple Stressors and Biodiversity Loss on the Functioning of Freshwater Microbial Communities

大量证据表明，在许多地区和分类类群中，生物多样性水平较高的生态系统也更有生产力和稳定性。由土地利用变化、污染和入侵物种等因素驱动的生物多样性丧失与快速的全球环境变化（如变暖、酸化、富营养化）同时发生，但我们对这些环境变化的多个方面对生态系统功能的潜在协同作用的理解严重有限，因为大多数生物多样性丧失的实验操作都是在环境环境下进行的。理论表明，决定环境耐受性的性状变异在调节非生物变化对生态动力学和生态系统功能的影响中发挥了关键作用。如果物种丧失独立于环境耐受特性发生（如土地利用变化、养分负荷或入侵物种的影响所预期的那样），那么非生物环境变化的额外影响可能导致生态系统功能的显著下降，因为物种较少的群落将有更低的可能性包括那些具有使其能够应对新环境制度的特征的物种。随着环境压力源数量的增加，可能需要越来越多的物种（和特征）来维持生态系统的功能。该项目将使用微生物群落的高通量实验来验证这些假设。我们将从受到各种环境压力的淡水生态系统中分离出各种各样的微生物。我们将利用现有的实验，包括在多塞特的长期暖化中生态系统，冰岛的地热暖化溪流和Llyn Brianne实验水槽。我们还将利用CEH的智能河流网络地理信息系统工具来识别受到各种人为压力因素（例如营养负荷、重金属污染、酸化）影响的集水区。我们将利用埃克塞特大学、卡迪夫大学和CEH最先进的微生物生态学实验室的高通量技术，量化每种分离物对每种压力源变异的耐受性，以及压力源的因子组合。然后，分离物将在分类丰富度的log2尺度上组装成群落，以模拟生物多样性的丧失，并在析因实验中暴露于一系列非生物应激源。生态系统功能将被量化为群落生物量和使用高通量呼吸法测量的总呼吸CO2通量。我们将利用分离物的环境耐受性特征信息来了解多样性-功能关系如何以及为什么会被多个应激源改变，以及环境耐受性特征之间的协方差或权衡，这些信息可用于确定保护目标的关键分类类群。微生物群落是淡水食物网的基础，它们的生物多样性和生产力为人类社会提供了不可估量的服务——从清洁水到气候调节和渔业生产。与环境变化和生物多样性丧失对淡水微生物群落的影响形成鲜明对比的是，环境变化和生物多样性丧失对淡水微生物群落的影响仍然知之甚少，研究也严重不足。该项目将通过量化生物多样性丧失与多种非生物应激源之间的协同作用对淡水微生物群落功能的影响来解决这一关键知识缺口。

Substantial evidence exists across a wide variety of regions and taxonomic groups that ecosystems with higher levels of biodiversity are also more productive and stable. Biodiversity loss, driven by factors such as land use change, pollution, and invasive species, is occurring in parallel with rapid global environmental change (e.g. warming, acidification, eutrophication) yet our understanding of the potential for synergies between these multiple facets of environmental change on ecosystem functioning is severely limited because most experimental manipulations of biodiversity loss are conducted under ambient environments. Theory suggests that variance in traits that determine environmental tolerance should play a key role in mediating the impacts of abiotic change on ecological dynamics and ecosystem functioning. If species loss occurs independently of environmental tolerance traits (as might be expected from the effects of land-use change, nutrient loading, or invasive species), then the additional impact of changes in the abiotic environment could result in pronounced declines in ecosystem function, because communities with fewer species will have a lower probability of including those with traits that enable them to cope with the novel environmental regime. As the number of environmental stressors rise, an increasingly large number of species (and traits) may be required to maintain ecosystem functioning. This project will test these hypotheses using high-throughput experiments with microbial communities. We will isolate a wide range of microbes from freshwater ecosystems that have been subjected to diverse environmental stressors. We will capitalise existing experiments including long-term, warmed mesocosms in Dorset, geothermally warmed streams in Iceland and the Llyn Brianne experimental flumes. We will also utilize CEH's Intelligent River Network GIS tool to identify catchments that have been subjected to range of anthropgenic stressors (e.g. nutrient loading, heavy metal contamination, acidification). We will quantify the tolerance of each isolate to variation in each stressor as well as factorial combinations of stressors using high-throughput techniques in the state-of-the-art microbial ecology laboratories at the University of Exeter, Cardiff University and CEH. Isolates will then be assembled into communities across a log2 scale of taxonomic richness to simulate biodiversity loss and exposed to the range of abiotic stressors in factorial experiments. Ecosystem functioning will be quantified as community biomass and total respiratory CO2 flux measured using high-throughput respirometry. We will use information on the environmental tolerance traits of the isolates to understand how and why the diversity-functioning relationship is altered by multiple stressors as well as any covariance or trade-offs between environmental tolerance traits, which can be used to identify key taxonomic groups to target for conservation.Microbial communities are the foundation of freshwater food webs and their biodiversity and productivity provide services that are of incalculable value to human societies - from clean water to climate regulation and fisheries production. In stark contrast to their vital importance, the impacts of environmental change and biodiversity loss on freshwater microbial communities remain poorly understood and grossly understudied. This project will address this critical knowledge gap by quantifying the impacts of synergies between biodiversity loss and multiple abiotic stressors on the functioning of freshwater microbial communities.