Regime shifts in freshwater ecosystems exposed to multiple stressors by increasing temperature, fertilizers and pesticides

浅层淡水生境提供了重要的生态系统功能，但受到不同时空尺度多重压力因素的威胁。虽然对全球气候变化的反应可能是渐进的，但当局部压力源的额外影响超过临界阈值时，突变是可能的。分析多重压力源影响的困难在于解释其复杂性，因为压力源可能是相加的、协同的或拮抗的。CLIMSHIFT旨在从机制上理解作用于浅层水生系统的压力源相互作用，浅层水生系统由于其高地水比、大河岸界面和地下水连通性，特别容易受到气候变暖和农业径流的影响。底栖和远洋初级生产者和相关消费者的不同功能群之间复杂的相互作用导致稳定状态的发生，多种压力源可能引发这些状态之间的非线性变化，对关键的生态系统过程和功能产生深远的影响。我们的主要假设是，气温升高会增强农业径流的负面影响，包括硝酸盐、有机农药和铜。作为初级生产者的沉水植物、周围植物和浮游植物将与第二营养层的消费者（由蜗牛lynaea组成，消耗周围植物和植物）以及底栖和远洋浮游植物滤食性动物（Dreissena和Daphnia）相结合。我们将在两个不同的空间尺度上应用不同的暴露情景，以了解个人、社区和生态系统层面的影响。我们从实验室规模的微观世界开始，并将升级到更大的室外中观世界。在整个项目中，我们将使用建模来模拟潜在的结果和临界阈值，并预测压力源的相互作用。模型开发将与所有工作包密切合作，以确定最合适的建模方法，整合经验结果，联系不同的空间和时间尺度，推广和推断结果，并制定和检验假设。我们预计，在这些高度耦合的系统中，综合压力因素将导致社区结构的突然转变。预计水下大型植物将被浮游植物或底栖藻类所取代，这将对重要的生态系统功能产生重大影响。我们的建议的优势在于，常见的生态毒理学压力指标，如不同生物体的生长和生物标志物，将与功能群落/生态系统方法相结合，研究生态系统的代谢和动态。5个实验室的专业知识相结合，具有互补性和所有必要的设施，将确保项目的可行性。我们项目的成果可以帮助在不断变化的世界中定义可持续农业和浅水系统管理的安全操作空间。

Shallow freshwater habitats provide vital ecosystem functions but are threatened by multiple stressors acting at different spatial and temporal scales. While a response to global climate change might be gradual, abrupt changes are possible when critical thresholds by additional effects of local stressors are exceeded. The difficulty in analysing effects of multiple stressors is to account for complexity, as stressors may act additive, synergistic or antagonistic. CLIMSHIFT aims for a mechanistic understanding of stressor interactions acting on shallow aquatic systems, which are especially vulnerable to climate warming and agricultural run-off due to their high surface to water ratios, large riparian interface and groundwater connectivity. The complex interactions between different functional groups of benthic and pelagic primary producers and associated consumers result in the occurrence of stable regimes, and multiple stressors may trigger non-linear shifts between those regimes, with far-reaching effects on crucial ecosystem processes and functions. Our main hypothesis is that increased temperature will enhance negative effects of agricultural run-off, containing nitrates, organic pesticides and copper. Submerged plants, periphyton and phytoplankton as primary producers will be combined with the second trophic level, consumers, composed of the snail Lymnaea, consuming periphyton and plants, and benthic and pelagic phytoplankton filter-feeders, Dreissena and Daphnia. We will apply different exposure scenarios at two different spatial scales to understand effects at the individual, community and ecosystem level. We start with investigations in microcosms at laboratory scale, and will upscale to larger, outdoor mesocosms. Throughout the project, we will use modelling to simulate potential outcomes and critical thresholds, and predict stressor interactions. Model development will be conducted in close collaboration with all work packages to identify the most appropriate modelling approach, integrate empirical results, link different spatial and temporal scales, generalize and extrapolate results, and develop and test hypotheses. We expect that combined stressors will lead to sudden shifts in community structure in these highly coupled systems. Submerged macrophytes are expected to be replaced by phytoplankton or benthic algae, with major consequences for important ecosystem functions. The strength of our proposal is that common ecotoxicological stress indicators such as growth and biomarkers of the different organisms will be combined with functional community/ecosystem approaches looking at ecosystem metabolism and dynamics. The combined expertise of 5 laboratories with complementary expertise and all necessary facilities will ensure the project feasibility. The outcome of our project can help defining safe operating spaces for a sustainable agriculture and management of shallow aquatic systems in a changing world.