Establishing environmental DNA (eDNA) monitoring for causal analysis of amphibian occupancy and aquatic ecosystem risk assessment

在加拿大各地，淡水湿地的数量和质量都在迅速下降，迫切需要了解其下降的原因，并制定有效监测和评估的协议。两栖动物是水生生态系统的重要组成部分，但在世界范围内，它们的数量正在下降，在加拿大，一些物种被列为濒危物种，或者从明显适宜的栖息地消失。两栖动物的减少和局部灭绝可能与其水生栖息地的恶化有关，包括与水媒病原体（壶菌、ranavirus）直接或相互作用于其他环境压力源（如气候、污染物、栖息地丧失）有关的死亡。然而，大多数两栖动物数量下降的确切原因尚不清楚，这主要是由于种群监测不足，以及数量趋势与环境压力之间的因果关系不强；这种趋势可能预示着淡水质量和水生系统服务的变化。利用新的动物调查方法，利用环境DNA （eDNA）和改进的景观制图和建模技术，这项工作将为观察到的两栖动物发生模式的原因提供严格的评估。具体来说，我们将：1)在加拿大环境下建立水基采样方案，用于检测和量化两栖动物及其主要病原体（壶菌，ranavirus）；2)利用与实地收集数据相关的土地覆盖和环境变量（湿度、污染物）来开发两栖动物和病原体占用的模型，并评估其作为湿地质量生物指标的效用；3)建立模型

Across Canada, freshwater wetlands are rapidly declining in number and quality, and there is an urgent need to understand the causes of their decline and develop protocols for their effective monitoring and assessment. Amphibians are important components of aquatic ecosystems but worldwide their populations are declining, and in Canada several species are listed at-risk or are absent from apparently suitable habitat. Amphibian declines and local extinctions likely are related to deterioration of their aquatic habitat, including mortality associated with water-borne pathogens (chytrid fungus, ranavirus) acting either directly or interactively with other environmental stressors (e.g., climate, contaminants, habitat loss). However, the precise cause of most amphibian declines is poorly known due to inadequate population monitoring combined with weak causal relationships between numerical trends and environmental stressors; such trends may portend changes in freshwater quality and aquatic system services. Capitalizing on new animal survey methods using environmental DNA (eDNA), and improved landscape mapping and modeling techniques, this work will provide a rigorous assessment of the causes of observed amphibian occurrence patterns. Specifically, we will: 1) Establish water-based sampling protocols for detecting and quantifying amphibians and their primary pathogens (chytrid fungus, ranavirus) in a Canadian context; 2) Use land cover and environmental variables (moisture regimes, contaminants) associated with field-collected data to develop models for amphibian and pathogen occupancy, and assess their utility as bioindicators of wetland quality; and 3) Develop models establishing likely causal links between amphibian occupancy and environmental stressors. This research will be among the first to adopt a comprehensive and multivariate approach to understand amphibian occupancy and wetland quality. These advances will lead to robust understanding of the relationship between amphibian populations and environmental stressors, and contribute to the development of state-of-the-art and truly 'world class' freshwater monitoring systems.