Although microplastics are a recognised pollutant in marine environments, less attention has been directed towards freshwater ecosystems despite their greater proximity to possible plastic sources. Here, we quantify the presence of microplastic particles (MPs) in river organisms upstream and downstream of five UK Wastewater Treatment Works (WwTWs). MPs were identified in approximately 50% of macroinvertebrate samples collected (Baetidae, Heptageniidae and Hydropsychidae) at concentrations up to 0.14 MP mg tissue⁻¹ and they occurred at all sites. MP abundance was associated with macroinvertebrate biomass and taxonomic family, but MPs occurred independently of feeding guild and biological traits such as habitat affinity and ecological niche. There was no increase in plastic ingestion downstream of WwTW discharges averaged across sites, but MP abundance in macroinvertebrates marginally increased where effluent discharges contributed more to total runoff and declined with increasing river discharge. The ubiquity of microplastics within macroinvertebrates in this case study reveals a potential risk from MPs entering riverine food webs through at least two pathways, involving detritivory and filter-feeding, and we recommend closer attention to freshwater ecosystems in future research.

尽管微塑料是海洋环境中公认的污染物，但尽管它们更接近可能的塑料来源，但对淡水生态系统的关注却较少。在这里，我们量化了五个英国废水处理厂（WwTWs）上游和下游的河流生物中存在的微塑料颗粒（MPs）。在收集到的大约50％的大型无脊椎动物样品（H科，七子科和水生科）中鉴定出MPs，其浓度最高为0.14 MP mg组织^-1 ，它们均出现在所有部位。MP的丰度与大型无脊椎动物的生物量和分类学家族有关，但MP的发生与进食行会和生物特征（如栖息地亲和力和生态位）无关。。各个站点的WwTW排放量下游的塑料摄入量均没有增加，但大型无脊椎动物的MP含量略有增加，其中污水排放量对总径流量的贡献更大，并随着河流排放量的增加而下降。在本案例研究中，大型无脊椎动物中普遍存在微塑料，这表明国会议员通过至少两种途径进入河流食物网的潜在风险，包括破坏性和滤食性进食，我们建议在未来的研究中更加关注淡水生态系统。