Mechanisms and thresholds of fungicide effects on microbial communities and organic matter processing

在第一个项目阶段，我们研究了杀菌剂对溪流中有机物处理的影响。我们发现，田间试验中杀菌剂的毒性梯度与微生物群落的变化和微生物有机物处理的下降有关。在第二个项目阶段，我们将仔细研究杀菌剂对微生物群落的影响机制，以及对有机物加工的潜在繁殖。此外，我们将调和田间观察和在受控条件下(例如微观世界和中微体)关于杀菌剂的少数研究之间的阈值水平不匹配。在第一个工作包中，我们仔细研究了杀菌剂对微生物叶加工的影响机制。这项实验遵循了一个复杂的测试设计，该设计考虑了现场情况的关键要素，即重复曝光、粉碎机的进料压力和多个定居-分解周期。这项实验将在全球6个地方使用典型的无脊椎动物粉碎机和树叶(来自澳大利亚、加拿大、德国、丹麦、哥斯达黎加和瑞典的实验室联盟)进行，并将采用接触模式，混合使用从全球地表水中杀菌剂浓度分析得出的混合物。此外，该实验将在叶片材料方面出现几次有机材料的周转，这意味着潜在的影响可能会累积。后者已在初步实验中得到证实。测量的终点包括叶片加工率、无脊椎动物生长以及微生物群落组成和生物量。我们将推导杀菌剂的效果阈值，并假设影响随着时间的积累而积累，这解释了实验室和田间研究之间的效果阈值差异。第二个工作方案旨在建立杀菌剂毒性与微生物群落和有机物处理的潜在变化之间的更强联系。它的特点是对每条具有高和低杀菌剂毒性的6条溪流进行实地研究，其中将选择一个位于森林边缘的原始上游地点和一个位于葡萄种植区的下游地点(即总共24个地点)。实地调查将跨越杀菌剂使用前和随后的杀菌剂使用期，并包括比较上下游地点的微生物群落和微生物加工。种植在葡萄种植区上游和下游的叶袋将被用来识别(1)群落组成和有机物加工的差异及其与杀菌剂施用期和杀菌剂毒性的关系，以及(2)污染状况对微生物定植的影响。总体而言，这一后续项目将提供机制解释和杀菌剂毒性与生态终点之间因果关系的进一步证据。

In the first project phase, we examined effects of fungicides on organic matter processing in streams. We found that the fungicide toxicity gradient in the field study was associated with changes in microbial communities and a decline in microbial organic matter processing. In the second project phase, we will scrutinise effect mechanisms of fungicides on microbial communities and the potential propagation to organic matter processing. In addition, we will reconcile the mismatch regarding threshold levels between field observations and the few studies on fungicides under controlled conditions (e.g. microcosms, mesocosms). In the first work package, we scrutinise the effect mechanisms of fungicides on microbial leaf processing. The experiment follows a complex test design that considers crucial elements of the field situation, namely repeated exposure, feeding pressure by shredders and multiple cycles of colonisation-decomposition. The experiment will be run in 6 places worldwide using typical invertebrate shredders and leafs (consortium of laboratories from Australia, Canada, Germany, Denmark, Costa Rica and Sweden) and will employ an exposure pattern with mixtures derived from a global analysis of fungicide concentrations in surface waters. In addition, the experiment will feature several turnovers of organic material in terms of leaf material, which means that potential effects can cumulate. The latter has been demonstrated in a preliminary experiment. The measured endpoints include the leaf processing rate, invertebrate growth and microbial community composition and biomass. We will derive effect thresholds for fungicides and hypothesise that the effects cumulate over time and that this explains differences in effect thresholds between laboratory and field studies.The second work package aims to establish a stronger link between fungicide toxicity and potential changes of microbial communities and organic matter processing. It features a field study with each of 6 streams with high and low fungicide toxicity, where one pristine upstream site at the edge of the forest and one downstream site in the viticultural area will be selected (i.e. a total of 24 sites). The field survey will span the pre-fungicide application and the following fungicide application period and includes the comparison of microbial communities and microbial processing between upstream and downstream sites. Leaf bags colonised in pristine upstream reaches and in downstream reaches in the viticultural area will be employed to identify (1) differences in the community composition and organic matter processing and its relation to the fungicide application period and fungicide toxicity and (2) the implications of the pollution state for microbial colonisation. Overall, this follow-up project will provide mechanistic explanation and further evidence of causality of fungicide toxicity with ecological endpoints.