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

诊断河流生态系统退化的原因是困难的，因为河流生物同时暴露于多种环境压力因素（例如，有毒化学物质、营养物质、悬浮沉积物），这些环境压力因素会对它们产生不利影响。虽然环境压力源可以对生物群落产生复杂的、相互作用的影响，但这些累积的后果在监管指南中很少被考虑。生活在排水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，以提高对农药、过量营养物质和沉积物对农业河流食物网的相互作用的认识。本研究将：(1)建立常用农药单独使用和组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实验，研究营养物在掩盖农药作用方面可能起的作用；(3)在模拟的农业梯度上测试农药、养分和过量沉积物对河流无脊椎动物的综合影响。主要预测如下：(1)河流昆虫对非致死农药暴露的反应是丰度和体型的减少；(2)这些负面影响将被轻度的养分污染所缓和；(3)沉降会加重农药的负面影响。该研究将培养2名硕士、2名博士和5名本科生，并增加我们对营养-污染物-沉积物对河流群落影响的认识。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全世界最受威胁的生态系统之一。

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.