Cothran, R. D., F. Radarian, and R. A. Relyea. 2011. Altering aquatic food webs with a global insecticide: Arthropod-amphibian links in mesocosms that simulate wetland communities. Journal of the North American Benthological Society 30:893-912.

Pesticides play a critical role in maximizing yields of economically important crops and minimizing the human health threats of disease-carrying pests, but they often have collateral effects on nontarget species. We used a mesocosm study to address how the most commonly used insecticide in the USA, malathion, applied at low, ecologically relevant concentrations (20 and 110 mg/L) affects species interactions in aquatic communities. Unlike many community ecotoxicology studies, our study assessed how malathion affects both consumptive and nonconsumptive effects of predators. We also considered how the vertical distribution of predator cues and malathion (caused by potential stratification) affects species interactions. We found no evidence for vertical stratification of malathion, a result suggesting that exposure to the pesticide was uniform throughout the water column. Malathion was lethal to some primary consumers (cladocerans) at both concentrations and to top predators (dragonflies) at the highest concentration (110 mg/L). These lethal effects initiated density-mediated indirect effects in both cases. Malathion also may have decreased dragonfly foraging efficiency, resulting in increased tadpole survival (trait-mediated indirect effect), which decreased the resources used by tadpoles (periphyton). Collectively, our results show that malathion alters species interactions. However, we suggest that the degree to which pesticides affect aquatic communities will depend strongly on the species composition of communities. Therefore, the community-level consequences of pesticide exposure are likely to vary across the ecological landscape.农药在提升经济作物产量、防控病媒害虫以降低人类健康风险方面发挥着关键作用，但其往往会对非靶标物种产生附带影响。本研究通过中宇宙（mesocosm）实验，探究美国最常用的杀虫剂马拉硫磷（malathion）在低浓度、符合生态实际的剂量（20与110 mg/L）下，对水生群落物种互作的影响。与多数群落生态毒理学（community ecotoxicology）研究不同，本研究同时评估了马拉硫磷对捕食者消费性效应（consumptive effects）与非消费性效应（nonconsumptive effects）的影响。本研究还探讨了捕食者信号（predator cues）与马拉硫磷的垂直分布（由潜在的水体分层引发）如何影响物种互作。研究未发现马拉硫磷存在垂直分层的证据，这一结果表明农药在整个水体柱（water column）中的暴露浓度均一。两种浓度下的马拉硫磷均对部分初级消费者枝角类（cladocerans）具有致死性，而最高浓度（110 mg/L）的药剂还对顶级捕食者蜻蜓稚虫（dragonflies）造成了致死伤害。上述致死效应在两种场景下均引发了密度介导的间接效应（density-mediated indirect effects）。马拉硫磷还可能降低了蜻蜓稚虫的觅食效率，进而提升了蝌蚪的存活率，即性状介导的间接效应（trait-mediated indirect effects），而蝌蚪存活率的上升则减少了其赖以生存的资源——周丛藻类（periphyton）的可用量。综上，本研究结果表明马拉硫磷会改变物种间的互作关系。但本研究认为，农药对水生群落的影响程度将在很大程度上取决于群落的物种组成。因此，农药暴露所带来的群落层面后果，在不同生态景观中很可能存在差异。