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

在加拿大，使用单一物种毒性试验的数据，在制定水质指南时，每种污染物都被单独考虑。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，水生生物群受到杀虫剂和营养物质混合物的影响。不幸的是，在生态风险评估中很少考虑营养丰富，更不用说群落复杂性了。相反，对实验室饲养的物种进行单一应激源的致死毒性测试是常态。需要一种更全面的方法。 拟议的研究将利用现有方法(例如，社区反应的致死性和结构性指标)开发一种综合方法，同时增加亚致死性的诊断指标(代谢组学，或生物体内的总代谢物)，以提供诊断营养物质和农药对河流食物网的交互影响所需的基础。这项工作将：(1)通过评估加性、乘性和比较效应模型框架，确定营养丰富和农药对河流昆虫的单独和联合影响；(2)通过操纵性中观实验，研究营养物质在掩盖农药影响方面可能发挥的作用；以及(3)评估跨农药干扰梯度的营养补贴的综合影响。关键的预测是：(1)河流昆虫将通过减少个体大小和丰度来应对非致命性压力；(2)农药的负面影响可以通过轻度到中度的营养强化来减轻；以及(3)营养丰富的增加将使农药暴露的影响恶化。 这项拟议的研究将培训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交互影响的知识。这项研究还将有助于将监管水质制度从简单的单一应激源影响模型转变为对多重应激源暴露造成的累积生态影响的更现实的评估。

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.