Antibiotics may constitute a risk for aquatic detritivorous macroinvertebrates (i.e., shredders) via waterborne and dietary antibiotic exposure. In addition, antibiotics can alter the food quality for shredders mediated by shifts in leaf-associated decomposer (i.e., aquatic fungi and bacteria) communities. However, little is known about the relative importance of the waterborne and dietary effect pathway. Therefore, we followed a tiered testing approach aimed at assessing the relative importance of these effect pathways. We employed the antibiotic ciprofloxacin (CIP) and the shredder Gammarus fossarum as model stressor and test species, respectively. In a first step, we assessed the short-term waterborne toxicity of CIP using survival and leaf consumption of G. fossarum as response variables. Alterations in the leaf-associated decomposer community, which may be reflected by their palatability, were assessed using food choice assays. Finally, we conducted a 2 × 2-factorial experiment over 24 days assessing the pathways individually and combined using energy processing (i.e., leaf consumption and feces production), growth and energy storage (i.e., neutral lipid fatty acids) as variables. Short term waterborne exposure indicated low toxicity with LC50 and EC50 values of 13.6 and 6.4 mg CIP/L, respectively. At the same time, shredders did not prefer any leaf material during the food choice assay. However, the fungal community was significantly affected in the highest CIP-treatments (0.5 and 2.5 mg/L) suggesting an altered food quality for shredders. This assumption is supported by the results of the long-term assay. At 0.5 mg CIP/L, gammarids' leaf consumption, growth and energy storage were increased when subjected via the dietary pathway, which was linked to changes in the leaf-associated microbial community. Our data highlight the importance of dietary effect pathways for effects on shredders, potentially impacting energy dynamics in detritus-based stream ecosystems.

中文翻译：

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与饮食有关的抗生素环丙沙星对切碎无脊椎动物无脊椎动物Gammarus fossarum（甲壳纲；两栖动物）的饮食相关作用的重要性。

抗生素可能会通过水和饮食中的抗生素接触而对水生有害无脊椎动物（即切碎机）构成风险。另外，抗生素可以改变与叶相关的分解物（即水生真菌和细菌）群落的变化介导的切碎机的食品质量。然而，关于水和饮食影响途径的相对重要性知之甚少。因此，我们遵循了旨在评估这些效应途径相对重要性的分层测试方法。我们分别采用了抗生素环丙沙星（CIP）和切碎的Gammarus fossarum作为模型应激源和测试物种。在第一步中，我们使用survival草的存活和叶片消耗作为响应变量，评估了CIP的短期水生毒性。与叶相关的分解器社区中的变更，可以通过食物选择分析评估其适口性。最后，我们在24天中进行了2×2因子实验，分别评估了途径，并使用能量加工（即叶片消耗和粪便产生），生长和能量存储（即中性脂质脂肪酸）作为变量进行了组合。短期水接触表明低毒，LC50和EC50值分别为13.6和6.4 mg CIP / L。同时，在食物选择检测过程中，切碎机不喜欢任何叶片材料。但是，在最高的CIP处理（0.5和2.5 mg / L）下，真菌群落受到显着影响，表明切碎机的食品质量发生了变化。长期测定的结果支持了这一假设。在0.5 mg CIP / L时，γ射线的叶片消耗量为 通过饮食途径增加其生长和能量存储，这与叶相关微生物群落的变化有关。我们的数据强调了饮食效应途径对切碎机的影响的重要性，这可能会影响碎屑流生态系统中的能量动态。