Development of diagnostic indicators for assessing effects of multiple stressors on stream ecosystem health.

在加拿大，利用单一物种毒性试验的数据制定水质准则时，对每种污染物都分别加以考虑。然而，污染物和物种都不是孤立存在的。例如，在农业系统中，由于喷雾漂移、径流和侵蚀，水生生物群受到农药和营养物混合物的影响。不幸的是，营养富集，更不用说社区的复杂性，但很少考虑在生态风险评估。相反，在实验室饲养的物种中对单一压力源进行致死毒性测试是常态。需要采取更全面的办法。 拟议的研究将利用现有方法（例如，生物多样性指数（生物多样性指数、致死率和群落反应的结构指标），同时增加亚致死性诊断指标（代谢组学或生物体内的总代谢物），为诊断营养物质和农药对河流食物网的相互影响提供必要的基础。这项工作将：（1）通过评估加性效应、倍增效应和比较效应模型框架，确定养分富集和农药对河流昆虫的单独和组合效应;（2）通过操纵性围隔实验，研究养分在掩盖农药效应方面可能发挥的作用;（3）评估养分补贴在农药干扰梯度上的综合效应。关键预测是：（1）河流昆虫会通过减小体型和减少数量来应对非致命性压力;（2）轻度至中度的营养富集可能会减轻农药的负面影响;（3）增加营养富集会加剧农药暴露的影响。 这项研究将培养2名博士，4名硕士和5名本科生，并增加我们对水生大型无脊椎动物群落中营养物质和农药暴露的相互作用的认识。这项研究也将有助于移动监管水质制度从简单的，单一的压力影响模型，以更现实的评估累积生态影响造成的多个压力暴露。

Each contaminant is considered separately in the development of water quality guidelines in Canada using data from single-species toxicity tests. However, neither contaminants nor species exist in isolation. For example, in agricultural systems, aquatic biota are impacted by mixtures of pesticides and nutrients due to spray drift, runoff and erosion. Unfortunately, nutrient enrichment, let alone community complexity, are but rarely considered in ecological risk assessment. Rather, lethal toxicity testing of single stressors in laboratory-reared species is the norm. A more holistic approach is needed. The proposed research will develop a combined approach using existing methods (e.g., lethality and structural indicators of community responses) while adding sublethal, diagnostic indicators (metabolomics, or the total metabolites within an organism) to provide the building blocks needed to diagnose the interactive effects that nutrients and pesticides have on food webs in rivers. This work will: (1) establish the effects of nutrient enrichment and pesticides on riverine insects, both alone and in combination by assessing additive, multiplicative and comparative effects model frameworks; (2) examine the role nutrients may have in masking the effects of pesticides through manipulative mesocosm experiments; and (3) assess the combined effects of nutrient subsidies across pesticide disturbance gradients. Key predictions are that: (1) river insects will respond to non-lethal stress through decreased body size and abundance; (2) negative effects of pesticides may be lessened by mild to moderate nutrient enrichment; and (3) increased nutrient enrichment will worsen the effects of pesticide exposure. The proposed research will train 2 PhD, 4 MSc, and 5 undergraduate students, and increase our knowledge of the interactive effects of nutrient and pesticide exposure in aquatic macroinvertebrate communities. This research will also help move regulatory water quality regimes from simple, single-stressor effects models to a more realistic evaluation of cumulative ecological effects resulting from multiple stressor exposure.