Anthropogenic activities influence the natural equilibrium of freshwater ecosystems resulting in negative ecological impacts. Differences in the infection variables of Lamproglena clariae in relation to variable water quality influenced by metal pollution were studied at six sites along the Vaal River, South Africa (March 2017 and October 2018). From each sampling site, in situ water quality parameters, water and sediment samples, and a minimum of 10 Clarias gariepinus were collected. Lamproglena clariae specimens collected from the gills of C. gariepinus were used to calculate the prevalence, mean intensity, and mean abundance of the parasite. Metal concentrations in water and sediment were analysed with inductively coupled plasma-optical emission spectrometry and inductively coupled plasma-mass spectrometry. Parasite intensity correlated negatively with some water quality parameters (conductivity, salinity, pH, total dissolved solids, and dissolved oxygen). Negative correlations were found between L. clariae (intensity and prevalence) and metal concentrations (Cu, Cr, Zn, Cd) in water. Parasite infections were influenced negatively at sites with high metal concentrations recorded in sediment and water and high levels of organic pollution. Sites that were found to be more polluted had lower mean intensity and mean abundance of L. clariae, indicating pollution affects the survival of this ectoparasite.

中文翻译：

---

寄生虫作为生物指标：环境质量对南非瓦尔河沿岸鲶鱼（甲壳纲）感染的影响。

人为活动影响淡水生态系统的自然平衡，导致负面的生态影响。在南非瓦尔河沿岸的六个地点（2017 年 3 月和 2018 年 10 月）研究了与受金属污染影响的可变水质相关的兰氏蓝藻感染变量的差异。从每个采样点采集原位水质参数、水和沉积物样品，以及至少 10 条鲢鱼。使用从 C. gariepinus 的鳃中采集的兰普罗格莱纳 (Lamproglena clariae) 标本来计算寄生虫的流行率、平均强度和平均丰度。用电感耦合等离子体发射光谱法和电感耦合等离子体质谱法分析水和沉积物中的金属浓度。寄生虫强度与一些水质参数（电导率、盐度、pH、总溶解固体和溶解氧）呈负相关。L. clariae（强度和流行率）与水中的金属浓度（Cu、Cr、Zn、Cd）之间存在负相关。在沉积物和水中记录的高金属浓度以及高水平有机污染的地点，寄生虫感染受到负面影响。污染较重的地点的 L. clariae 的平均强度和平均丰度较低，表明污染影响了这种外寄生虫的生存。在沉积物和水中记录的高金属浓度以及高水平有机污染的地点，寄生虫感染受到负面影响。污染较重的地点的 L. clariae 的平均强度和平均丰度较低，表明污染影响了这种外寄生虫的生存。在沉积物和水中记录的高金属浓度以及高水平有机污染的地点，寄生虫感染受到负面影响。污染较重的地点的 L. clariae 的平均强度和平均丰度较低，表明污染影响了这种外寄生虫的生存。