School of Biosciences, Cardiff University, UK; Department of Biosciences, University of Exeter, UK.
Centre for Ecology and Hydrology, Lancaster, UK.
Water Res. 2019 Oct 15;163:114858. doi: 10.1016/j.watres.2019.114858. Epub 2019 Jul 13.
Urban areas contribute substantially to xenobiotic contaminant loads in rivers, but their effects have been investigated more for individual organisms and sensitive taxa, rather than through the emergent properties of communities. Here, we use replicated, catchment-scale sampling of benthic invertebrates and novel multivariate techniques to assess whether urban wastewater contaminants affected the structure and function of river food webs. We postulated that the continued occurrence of selected contaminants in river systems might explain the incomplete recovery of urban rivers from legacy gross pollution. Benthic invertebrate communities were sampled monthly over a year (2016-2017) at 18 sites across 3 river systems in South Wales (United Kingdom). Contaminant sources were characterised using remote sensing, water quality data from routine monitoring and measured concentrations of selected persistent xenobiotic pollutants (polychlorinated biphenyls and polybrominated diphenyl ethers). Urban wastewater discharges had relatively limited effects on river water quality, with small increases in nitrate, phosphate, temperature, conductivity and total dissolved solids in urban systems. Concentrations of polychlorinated biphenyls and polybrominated diphenyl ethers in invertebrates, however, were significantly higher under greater urban land cover and wastewater discharge. Food webs at the most highly contaminated urban sites were characterised by: (i) reduced taxonomic and functional diversity; (ii) simplified food web structure with reduced network connectance; and (iii) reductions in the abundance of prey important for apex predators such as the Eurasian dipper (Cinclus cinclus). Although correlative and partially confounded by other effects, these data provide support for the hypothesis that impairment to food webs resulting from urban pollutants might explain population, community and ecosystem-level effects in urban river systems, and hence incomplete recovery from past pollution.
城市地区对河流中的外来污染物负荷有很大的贡献，但它们的影响在个别生物和敏感类群中得到了更多的研究，而不是通过群落的新兴特性来研究。在这里，我们使用复制的、集水区规模的底栖无脊椎动物采样和新的多元技术来评估城市废水污染物是否影响了河流食物网的结构和功能。我们假设，在河流系统中持续存在选定的污染物可能解释了城市河流从遗留的总污染中不完全恢复的原因。在威尔士南部的 3 个河流系统的 18 个地点，我们在一年（2016-2017 年）中每月对底栖无脊椎动物群落进行采样。使用遥感技术、常规监测的水质数据和选定的持久性外来污染物（多氯联苯和多溴二苯醚）的测量浓度来描述污染物来源。城市废水排放对河水水质的影响相对有限，只有硝酸盐、磷酸盐、温度、电导率和总溶解固体在城市系统中略有增加。然而，无脊椎动物中多氯联苯和多溴二苯醚的浓度在城市土地覆盖和废水排放量较大的情况下显著更高。在污染最严重的城市地点，食物网的特征是：（i）减少分类和功能多样性；（ii）简化食物网结构，减少网络连接度；（iii）减少对欧亚河乌（Cinclus cinclus）等顶级捕食者重要的猎物的丰度。尽管这些数据是相关的，并且部分受到其他效应的混淆，但它们支持这样的假设，即城市污染物对食物网的损害可能解释了城市河流系统中种群、群落和生态系统水平的效应，因此不能从过去的污染中完全恢复。
