Neonicotinoids are a class of insecticide with global impacts on natural environments. Due to their high solubility, they are frequently found in stream ecosystems where they have the potential to impact non-target biota. While environmental concentrations are generally below lethal levels for most organisms, there are concerns that sublethal exposures can impact aquatic insects, particularly mayflies, which are highly sensitive to neonicotinoids. Because sublethal doses of neonicotinoids can reduce mobility in mayflies, exposure could indirectly increase mortality due to predation by impairing their ability to avoid initial detection or escape predators. We examined whether exposure to the neonicotinoid clothianidin at a concentration below the 96-h EC50 (7.5 µg/L), would increase the predation risk of Stenacron and Stenonema mayfly nymphs by larval southern two-lined salamanders (Eurycea cirrigera) or eastern dobsonfly nymphs (Corydalus cornutus) using a controlled laboratory experiment. For Stenacron, we found significant interactive effects between pesticide and dobsonfly exposure that increased the hazard ratio (HR). The HR assesses risk relative to a control population, in this case mayflies in similar experimental conditions but without exposure to neonicotinoids or predators. With the addition of clothianidin, the HR of mayflies exposed to a dobsonfly nymph significantly increased from 1.8 to 6.2 while the HR for those exposed to salamanders increased from 7.6 to 12.5. For Stenonema, the HR initially decreased due to dobsonfly exposure (1 to 0.3) but increased when clothianidin and dobsonflies were combined (0.3 to 1.6). Our study shows that aquatic exposure to clothianidin can increase mortality for aquatic insects through predator pressure. Such indirect effects associated with neonicotinoid exposure warrant further investigation to expand our understanding of pesticide impacts to aquatic systems.

新烟碱类是一类对自然环境具有全球影响的杀虫剂。由于它们的高溶解度，它们经常出现在河流生态系统中，它们有可能影响非目标生物群。虽然环境浓度通常低于大多数生物的致死水平，但有人担心亚致死暴露会影响水生昆虫，尤其是对新烟碱类高度敏感的蜉蝣。由于亚致死剂量的新烟碱类物质会降低蜉蝣的活动能力，因此暴露可能会通过削弱它们避免初始检测或逃避捕食者的能力而间接增加捕食造成的死亡率。我们检查了暴露于低于 96 小时 EC50 (7.5 µg/L) 浓度的新烟碱类噻虫胺是否会增加Stenacron的捕食风险和Stenonema蜉蝣若虫的幼虫南部两线蝾螈 ( Eurycea cirrigera ) 或东部多布森蜉蝣若虫 ( Corydalus cornutus ) 使用受控实验室实验。对于Stenacron，我们发现农药和多布森蝇暴露之间存在显着的交互作用，从而增加了风险比 (HR)。HR 评估相对于对照组的风险，在这种情况下，蜉蝣在类似的实验条件下，但没有接触新烟碱类或捕食者。添加噻虫胺后，蜉蝣暴露于多布森蝇若虫的 HR 从 1.8 显着增加到 6.2，而暴露于蝾螈的蜉蝣 HR 从 7.6 增加到 12.5。对于Stenonema，HR 最初由于暴露于多布森蝇而降低（1 至 0.3），但当噻虫胺和多布森蝇结合时增加（0.3 至 1.6）。我们的研究表明，水生暴露于噻虫胺可通过捕食者压力增加水生昆虫的死亡率。这种与新烟碱暴露相关的间接影响值得进一步调查，以扩大我们对农药对水生系统影响的理解。