Water Research Institute and School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, UK.
Environment Agency, PO Box 12, Warrington WA4 1HG, UK.
Sci Total Environ. 2023 Jun 20;878:163107. doi: 10.1016/j.scitotenv.2023.163107. Epub 2023 Mar 25.
Uncertainty around the changing ecological status of European rivers reflects an evolving array of anthropogenic stressors, including climate change. Although previous studies have revealed some recovery from historical pollution in the 1990s and early-2000s, there are contrasting trends among pollutants across Europe and recovery may have stalled or been reversed. To provide more contemporary evidence on trends and status, here we investigate changes in English and Welsh river macroinvertebrate communities over almost 30 years (1991-2019) using a network of nearly 4000 survey locations. Analysis comprised: i) trends in taxonomic and functional richness, community composition and ecological traits, ii) gains, losses and turnover of taxa, and the overall homogeneity of macroinvertebrate communities nationally, and iii) an exploration of how temporal trends varied with catchment characteristics. Taxonomic richness increased, primarily in the 1990s, whilst a shift towards pollution-sensitive taxa continued throughout the study period, accompanied by a growing prevalence in traits such as preferences for fast-flowing conditions, coarser substrata, and 'shredding' or 'scraping' feeding strategies. Changes consistent with improvement occurred in both urbanised and agricultural catchments, but were more pronounced in urban rivers as they gained pollution sensitive taxa that were otherwise more prevalent in rural rivers. Overall, these results indicate continuing biological recovery from organic pollution, consistent with national scale trends in water quality. Results reemphasise the importance of looking at multiple facets of diversity, with periods of near-constant richness disguising changes in taxonomic and functional composition. Whilst this national-scale picture is broadly positive, we highlight the need to investigate more local variations or pollutants that depart from this aggregate picture.
欧洲河流生态状况的不确定性反映了一系列不断变化的人为压力因素，包括气候变化。尽管先前的研究已经揭示了 20 世纪 90 年代和 21 世纪初历史污染的一些恢复，但欧洲各地的污染物趋势存在差异，恢复可能已经停滞或出现逆转。为了提供有关趋势和现状的更现代证据，我们利用近 4000 个调查点的网络，调查了近 30 年来（1991-2019 年）英格兰和威尔士河流大型无脊椎动物群落的变化。分析包括：i）分类和功能丰富度、群落组成和生态特征的趋势，ii）分类群的增益、损失和周转率，以及全国大型无脊椎动物群落的整体同质性，以及 iii）探索时间趋势如何随流域特征而变化。分类丰富度增加，主要是在 20 世纪 90 年代，而对污染敏感类群的偏好持续整个研究期，同时伴随着快速流动条件、较粗基质和“撕碎”或“刮擦”觅食策略等特征的普遍增加。城市化和农业流域都出现了与改善一致的变化，但在城市河流中更为明显，因为它们获得了污染敏感类群，而这些类群在农村河流中更为普遍。总体而言，这些结果表明，有机污染的生物恢复仍在继续，与水质的国家规模趋势一致。结果再次强调了多方面多样性的重要性，因为接近恒定丰富度的时期掩盖了分类和功能组成的变化。尽管这种全国范围的情况总体上是积极的，但我们强调需要调查更多局部变化或偏离这种总体情况的污染物。
