Ecological effects of nutrient-contaminant-sediment interacations on riverine food webs

诊断河流生态系统退化的原因很困难，因为河流生物同时暴露在多种环境应激源(例如，有毒化学品、营养物、悬浮沉积物)中，这可能对它们产生不利影响。尽管环境应激源可能会对生物群落产生复杂的交互影响，但监管指南很少考虑这些累积后果。生活在排干农业景观的河流中的生物尤其危险，因为它们暴露在沉积物、营养物质和杀虫剂中。拟议中的研究将提供必要的基础知识，以提高对农药、过量营养物质和沉积物对农业河流中的食物网的交互影响的了解。这项研究将：(1)确定常用杀虫剂单独和联合使用对河流昆虫的影响，并评估相互竞争的预测模型；(2)通过在人工溪流中进行的实验，研究营养物质在掩盖杀虫剂影响方面可能发挥的作用；以及(3)测试杀虫剂、营养物质和模拟农业梯度上的过量沉积物对河流无脊椎动物的综合影响。关键的预测是：(1)河流昆虫将通过减少丰度和体型对非致命性农药暴露做出反应；(2)这些负面影响将被轻微的营养污染缓解；(3)沉积物将加剧农药的负面影响。这项研究将培训2名硕士、2名博士和5名本科生，并增加我们对营养物质-污染物-沉积物对河流群落影响的知识。这项工作将对管理农业水生生态系统产生重要影响，这些生态系统是加拿大和世界范围内受到最大威胁的一些生态系统。

Diagnosing the cause of degraded river ecosystem condition is difficult because river organisms are simultaneously exposed to multiple environmental stressors (e.g., toxic chemicals, nutrients, suspended sediments) that can adversely affect them. Although environmental stressors can have complex, interactive effects on biological communities, these cumulative consequences are rarely considered in regulatory guidelines. Organisms living in rivers draining agricultural landscapes are at particular risk because they are exposed to sediments, nutrients and pesticides. The proposed research will provide the building blocks needed to improve knowledge of the interactive effects that pesticides, excess nutrients and sediments have on food webs in agricultural rivers. The research will: (1) establish the effects on river insects of commonly used pesticides, both alone and in combination, and evaluate competing predictive models; (2) examine the role nutrients may have in masking the effects of pesticides through experiments conducted in artificial streams; and (3) test the combined effects on river invertebrates of pesticides, nutrients and excess sediments across a simulated agricultural gradient. Key predictions are that: (1) river insects will respond to non-lethal pesticide exposure through decreased abundance and body size; (2) these negative effects will be moderated by mild nutrient pollution; and (3) sedimentation will worsen the negative effects of pesticides. The research will train 2 MSc, 2 PhD and 5 undergraduate students, and increase our knowledge of nutrient-contaminant-sediment effects on river communities. The work will have important implications for managing agricultural aquatic ecosystems, which are some of the most threatened in Canada and worldwide.