Canada Centre for Inland Waters, Burlington, ON, Canada.
Ecotoxicology. 2013 Sep;22(7):1085-100. doi: 10.1007/s10646-013-1096-3. Epub 2013 Jul 6.
The ecological effect of simultaneous exposure to two nutrient gradients, three insecticides and different predator intensities was investigated over a 3-week period in 80 outdoor, artificial streams using field-collected benthic invertebrates. The experimental design consisted of a 2 × 5 factorial structure with two nutrient levels (oligotrophic or mesotrophic) and five concentrations of the ternary insecticide mixture consisting of the insecticides (chlorpyrifos, dimethoate and imidacloprid). Equivalent toxic unit doses were summed to create a ternary insecticide dose (e.g., 0.1 + 0.1 + 0.1 = 0.3 TU) resulting in a range of ternary insecticide mixture toxicity (i.e., control groundwater, 0.3, 0.6, 0.9 and 1.2 TU). Two genera of insect predators, Gomphus spp. (Odonata) and Agnetina spp. (Plecoptera) were also added into each replicate stream, at densities and sizes comparable to those found at our collection site, to evaluate how the contribution of predators may change in nutrient limited (oligotrophic) versus amended (mesotrophic) systems. We describe a causal mechanism whereby the combined action of nutrients and insecticides reshaped aquatic community structure by interacting through multiple pathways. Specifically, mesotrophic conditions reduced the toxic effects of ternary insecticide mixtures for aquatic insects which, in some cases, appeared to increase abundance of aquatic insects. However, higher levels of insecticides in mesotrophic streams negated this effect and were even more toxic; for example, to aquatic insect grazers than the same insecticide doses in oligotrophic treatment levels. Effects of predators were only significant in oligotrophic streams. Evidence is provided as to how nutrient and contaminant interactions can greatly complicate the assessment of community level responses to insecticide mixtures due to direct and indirect effects of the resulting changes in the density of different genera and functional feeding groups within a community.
在 80 个户外人工溪流中，使用野外采集的底栖无脊椎动物，进行了为期 3 周的研究，以调查同时暴露于两种营养梯度、三种杀虫剂和不同捕食者强度的生态效应。实验设计由一个 2×5 的因子结构组成，有两个营养水平（贫营养或中营养）和由杀虫剂（毒死蜱、乐果和吡虫啉）组成的三元杀虫剂混合物的五个浓度。将等效毒性单位剂量相加，以创建三元杀虫剂剂量（例如，0.1+0.1+0.1=0.3 TU），从而产生三元杀虫剂混合物毒性范围（即对照地下水、0.3、0.6、0.9 和 1.2 TU）。两种昆虫捕食者属，Gomphus spp.（蜻蜓目）和 Agnetina spp.（蜉蝣目）也被添加到每个重复溪流中，其密度和大小与我们采集地点的相似，以评估在营养受限（贫营养）与改良（中营养）系统中，捕食者的贡献如何变化。我们描述了一个因果机制，即营养物质和杀虫剂的联合作用通过多种途径相互作用，重塑了水生群落结构。具体而言，中营养条件减少了三元杀虫剂混合物对水生昆虫的毒性作用，在某些情况下，这似乎增加了水生昆虫的丰度。然而，在中营养溪流中，更高水平的杀虫剂否定了这种效应，并且毒性更大；例如，对水生昆虫食草动物的毒性大于贫营养处理水平下相同剂量的杀虫剂。捕食者的影响仅在贫营养溪流中显著。由于不同属和功能摄食群落在群落中的密度变化的直接和间接影响，提供了证据表明营养物质和污染物相互作用如何极大地复杂化了对杀虫剂混合物引起的群落水平反应的评估。
