Dawoud Mohab, Bundschuh Mirco, Goedkoop Willem, McKie Brendan G
Department of Aquatic Sciences & Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden; Low Emission Capacity Building Project, 53 Misr- Helwan Elzerayea Rd., Lo'Lo'at Elmaadi Tower, Entrance C, Floor 5, Maadi, Cairo, Egypt.
Department of Aquatic Sciences & Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Aquat Toxicol. 2017 May;186:215-221. doi: 10.1016/j.aquatox.2017.03.008. Epub 2017 Mar 9.
Freshwater ecosystems are often affected by cocktails of multiple pesticides targeting different organism groups. Prediction and evaluation of the ecosystem-level effects of these mixtures is complicated by the potential not only for interactions among the pesticides themselves, but also for the pesticides to alter biotic interactions across trophic levels. In a stream microcosm experiment, we investigated the effects of two pesticides targeting two organism groups (the insecticide lindane and fungicide azoxystrobin) on the functioning of a model stream detrital food web consisting of a detritivore (Ispoda: Asellus aquaticus) and microbes (an assemblage of fungal hyphomycetes) consuming leaf litter. We assessed how these pesticides interacted with the presence and absence of the detritivore to affect three indicators of ecosystem functioning - leaf decomposition, fungal biomass, fungal sporulation - as well as detritivore mortality. Leaf decomposition rates were more strongly impacted by the fungicide than the insecticide, reflecting especially negative effects on leaf processing by detritivores. This result most like reflects reduced fungal biomass and increased detritivore mortality under the fungicide treatment. Fungal sporulation was elevated by exposure to both the insecticide and fungicide, possibly representing a stress-induced increase in investment in propagule dispersal. Stressor interactions were apparent in the impacts of the combined pesticide treatment on fungal sporulation and detritivore mortality, which were reduced and elevated relative to the single stressor treatments, respectively. These results demonstrate the potential of trophic and multiple stressor interactions to modulate the ecosystem-level impacts of chemicals, highlighting important challenges in predicting, understanding and evaluating the impacts of multiple chemical stressors on more complex food webs in situ.
淡水生态系统常常受到针对不同生物群体的多种农药混合物的影响。这些混合物对生态系统层面的影响的预测和评估很复杂，这不仅是因为农药本身之间可能存在相互作用，还因为农药会改变不同营养级之间的生物相互作用。在一项溪流微观实验中，我们研究了针对两个生物群体的两种农药（杀虫剂林丹和杀菌剂嘧菌酯）对一个由碎屑食性动物（等足目：普通等足虫）和消耗落叶的微生物（真菌丝孢菌组合）组成的模型溪流碎屑食物网功能的影响。我们评估了这些农药如何与碎屑食性动物的存在与否相互作用，以影响生态系统功能的三个指标——落叶分解、真菌生物量、真菌孢子形成——以及碎屑食性动物的死亡率。杀菌剂对落叶分解速率的影响比杀虫剂更强，这尤其反映出对碎屑食性动物处理落叶的负面影响。这个结果很可能反映了在杀菌剂处理下真菌生物量减少和碎屑食性动物死亡率增加。接触杀虫剂和杀菌剂都会使真菌孢子形成增加，这可能代表着应激诱导的繁殖体传播投资增加。在联合农药处理对真菌孢子形成和碎屑食性动物死亡率的影响中，应激源相互作用很明显，相对于单一应激源处理，联合处理分别降低和增加了真菌孢子形成和碎屑食性动物死亡率。这些结果证明了营养级和多种应激源相互作用调节化学物质对生态系统层面影响的潜力，突出了在原位预测、理解和评估多种化学应激源对更复杂食物网影响方面的重要挑战。
