Institute for Environmental Sciences, University of Koblenz-Landau, Landau, Germany.
Faculty of Biology, Aquatic Ecosystem Research, University of Duisburg-Essen, Essen, Germany.
Mol Ecol. 2019 Sep;28(18):4300-4316. doi: 10.1111/mec.15214. Epub 2019 Sep 18.
The Upper Rhine Valley, a "hotspot of biodiversity" in Germany, has been treated with the biocide Bacillus thuringiensis var. israelensis (Bti) for mosquito control for decades. Previous studies discovered Bti nontarget effects in terms of severe chironomid abundance reductions. In this study, we investigated the impact of Bti on species level and addressed the community composition of the nontarget family Chironomidae by use of community metabarcoding. Chironomid emergence data were collected in three mosquito-control relevant wetland types in the Upper Rhine Valley. For all three sites the chironomid species composition, based on operational taxonomic units (OTUs), was different to varying degrees in the Bti-treated samples versus control samples, ranging from a significant 63% OTU reduction to an OTU replacement. We assumed that predatory chironomids are less prone to Bti than filter feeders, as the latter feed on floating particles leading to direct ingestion of Bti. However, a comparable percentage of predators and filter feeders (63% and 65%, respectively) was reduced in the Bti samples, suggesting that the feeding strategy is not the main driver for Bti sensitivity in chironomids. Finally, our data was compared to a three-year-old data set, indicating possible chironomid community recovery due to species recolonization a few years after the last Bti application. Considering the currently discussed worldwide insect decline we recommend a rethinking of the usage of the biocide Bti, and to prevent its ongoing application especially in nature protection reserves to enhance ecological resilience and to prevent boosting the current biodiversity loss.
上莱茵河谷是德国的“生物多样性热点地区”，几十年来一直使用苏云金芽孢杆菌以色列变种（Bti）来控制蚊子。先前的研究发现 Bti 对摇蚊属生物产生了非靶向效应，导致其数量严重减少。在这项研究中，我们调查了 Bti 对物种水平的影响，并通过群落代谢组学研究了非靶向的摇蚊科的群落组成。我们在上莱茵河谷的三种与蚊子控制相关的湿地类型中收集了摇蚊的出现数据。对于所有三个地点，基于操作分类单位（OTUs）的摇蚊物种组成在 Bti 处理样本与对照样本之间存在不同程度的差异，从显著的 63%OTU 减少到 OTU 替换。我们假设捕食性摇蚊比滤食性摇蚊对 Bti 的敏感性较低，因为后者以漂浮颗粒为食，导致直接摄入 Bti。然而，在 Bti 样本中，捕食性和滤食性摇蚊的比例相当（分别为 63%和 65%），这表明摄食策略不是摇蚊对 Bti 敏感性的主要驱动因素。最后，我们将数据与三年前的数据集进行了比较，表明由于几年后最后一次 Bti 应用后的物种再殖民化，可能会出现摇蚊群落的恢复。考虑到目前全球昆虫数量减少的情况，我们建议重新考虑使用 Bti 生物农药，并防止其持续应用，特别是在自然保护区，以提高生态弹性，防止目前的生物多样性丧失加剧。
