This study demonstrates that independent additive effects of two human pharmaceuticals, the antibiotic trimethoprim and the artificial estrogen 17a-Ethinylestradiol (EE2), inhibit plant litter decomposition by aquatic microorganisms. The constant release of pharmaceuticals, such as these, has the potential to affect aquatic microbial metabolism and alter biogeochemical cycling of carbon and nutrients. Here we advance the Tea Bag Index (TBI) for decomposition by using it in a series of contaminant exposure experiments testing how interactions between trimethoprim and EE2 affect aquatic microbial activity. The TBI is a citizen science tool used to test microbial activity by measuring the differential degradation of green and rooibos tea as proxies for respectively labile and recalcitrant litter decomposition. Exposure to either trimethoprim or EE2 decreased decomposition of green tea, suggesting additive effects upon microbial activity. Exposure to EE2 alone decreased rooibos tea decomposition. Consequently, trimethoprim and EE2 stabilized labile organic matter against microbial degradation and restricted decomposition. We propose that the method outlined could provide a powerful tool for testing the impacts of multiple interacting pollutants upon microbial activity, at a range of scales, across aquatic systems and over ecologically relevant time scales.

该研究表明，抗生素甲氧苄氨嘧啶和人工雌激素 17a-乙炔雌二醇 (EE2) 这两种人类药物的独立加成作用可抑制水生微生物对植物凋落物的分解。此类药物的持续释放有可能影响水生微生物代谢并改变碳和营养物质的生物地球化学循环。在这里，我们通过在一系列污染物暴露实验中使用茶包指数 (TBI) 来推进分解，以测试甲氧苄啶和 EE2 之间的相互作用如何影响水生微生物活动。TBI 是一种公民科学工具，用于通过测量绿茶和路易波士茶的差异降解来测试微生物活动，分别作为不稳定和顽固的垃圾分解的代理。接触甲氧苄氨嘧啶或 EE2 会减少绿茶的分解，表明对微生物活性有累加作用。单独接触 EE2 会降低路易波士茶的分解。因此，甲氧苄氨嘧啶和 EE2 可以稳定不稳定的有机物质，防止微生物降解和限制分解。我们建议，所概述的方法可以提供一个强大的工具，用于测试多种相互作用的污染物对微生物活动的影响，在一定范围内，跨水生系统和生态相关的时间尺度。