Pesce Stéphane, Zoghlami Olfa, Margoum Christelle, Artigas Joan, Chaumot Arnaud, Foulquier Arnaud
Irstea, UR MALY, Centre de Lyon-Villeurbanne, 5 Rue de la Doua, CS70077, 69626 Villeurbanne Cedex, France.
Laboratoire Microorganismes: Génome et Environnement, Clermont Université, Université Blaise Pascal, Clermont-Ferrand, France; CNRS, UMR 6023, LMGE, Aubiere, France.
Aquat Toxicol. 2016 Apr;173:120-131. doi: 10.1016/j.aquatox.2016.01.012. Epub 2016 Feb 1.
Loss of biodiversity and altered ecosystem functioning are driven by the cumulative effects of multiple natural and anthropogenic stressors affecting both quantity and quality of water resources. Here we performed a 40-day laboratory microcosm experiment to assess the individual and combined effects of drought and the model fungicide tebuconazole (TBZ) on leaf litter decomposition (LLD), a fundamental biogeochemical process in freshwater ecosystems. Starting out from a worst-case scenario perspective, leaf-associated microbial communities were exposed to severe drought conditions (four 5-day drought periods alternated with 4-day immersion periods) and/or a chronic exposure to TBZ (nominal concentration of 20μgL(-1)). We assessed the direct effects of drought and fungicide on the structure (biomass, diversity) and activity (extracellular enzymatic potential) of fungal and bacterial assemblages colonizing leaves. We also investigated indirect effects on the feeding rates of the amphipod Gammarus fossarum on leaves previously exposed to drought and/or TBZ contamination. Results indicate a stronger effect of drought stress than fungicide contamination under the experimental conditions applied. Indeed, the drought stress strongly impacted microbial community structure and activities, inhibiting the LLD process and leading to cascading effects on macroinvertebrate feeding. However, despite the lack of significant effect of TBZ applied alone, the effects of drought on microbial functions (i.e., decrease in LLD and in enzymatic activities) and on Gammarus feeding rates were more pronounced when drought and TBZ stresses were applied together. In a perspective of ecological risk assessment and ecosystem management for sustainability, these findings stress the need for deeper insight into how multiple stressors can affect the functioning of aquatic ecosystems and associated services.
生物多样性丧失和生态系统功能改变是由影响水资源数量和质量的多种自然和人为压力源的累积效应驱动的。在此，我们进行了一项为期40天的实验室微观实验，以评估干旱和模型杀菌剂戊唑醇（TBZ）对落叶分解（LLD）的单独和联合影响，落叶分解是淡水生态系统中的一个基本生物地球化学过程。从最坏情况的角度出发，与叶片相关的微生物群落暴露于严重干旱条件下（四个5天的干旱期与4天的浸泡期交替）和/或长期暴露于TBZ（标称浓度为20μg L(-1)）。我们评估了干旱和杀菌剂对定殖在叶片上的真菌和细菌群落的结构（生物量、多样性）和活性（细胞外酶潜力）的直接影响。我们还研究了对先前暴露于干旱和/或TBZ污染的叶片上的双足类河蚬摄食率的间接影响。结果表明，在所应用的实验条件下，干旱胁迫比杀菌剂污染的影响更强。事实上，干旱胁迫强烈影响微生物群落结构和活性，抑制落叶分解过程，并对大型无脊椎动物的摄食产生连锁反应。然而，尽管单独施用TBZ没有显著影响，但当干旱和TBZ胁迫同时施加时，干旱对微生物功能（即落叶分解和酶活性降低）和对河蚬摄食率的影响更为明显。从生态风险评估和可持续性生态系统管理的角度来看，这些发现强调需要更深入地了解多种压力源如何影响水生生态系统及其相关服务的功能。
