Microbial organic matter decomposition is a critical ecosystem function, which can be negatively affected by chemicals. Although the majority of organic matter is stored in sediments, the impact of chemicals has exclusively been studied in benthic systems. To address this knowledge gap, we assessed the impact of a fungicide mixture at three concentrations on the decomposition of black alder leaves in the benthic and hyporheic zone. We targeted two sediment treatments characterized by fine and coarse grain sizes (1–2 vs. 2–4 mm). Besides microbial communities' functioning (i.e., decomposition), we determined their structure through microbial biomass estimates and community composition. In absence of fungicides, leaf decomposition, microbial biomass estimates and fungal sporulation were lower in the hyporheic zone, while the importance of bacteria was elevated. Leaf decomposition was reduced (40%) under fungicide exposure in fine sediment with an effect size more than twice as high as in the benthic zone (15%). These differences are likely triggered by the lower hydraulic conductivity in the hyporheic zone influencing microbial dispersal as well as oxygen and nutrient fluxes. Since insights from the benthic zone are not easily transferable, these results indicate that the hyporheic zone requires a higher recognition with regard to ecotoxicological effects on organic matter decomposition.

中文翻译：

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以下如上？杀菌剂对微生物有机质分解的影响在潜流区比在底栖区强

同时提高了细菌的重要性。在细沉积物中接触杀菌剂后叶片分解减少（40%），其影响大小是底栖区域（15%）的两倍多。这些差异可能是由影响微生物扩散以及氧气和养分通量的低流带中较低的水力传导率引发的。由于来自底栖区域的见解不容易转移，这些结果表明，在对有机物分解的生态毒理学影响方面，海流带需要更高的认识。这些差异可能是由影响微生物扩散以及氧气和养分通量的低流带中较低的水力传导率引发的。由于来自底栖区域的见解不容易转移，这些结果表明，在对有机物分解的生态毒理学影响方面，海流带需要更高的认识。这些差异可能是由影响微生物扩散以及氧气和养分通量的低流带中较低的水力传导率引发的。由于来自底栖区域的见解不容易转移，这些结果表明，在对有机物分解的生态毒理学影响方面，海流带需要更高的认识。