Institute for Water Research, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa.
Environ Monit Assess. 2010 Jul;166(1-4):581-94. doi: 10.1007/s10661-009-1025-3. Epub 2009 Jun 19.
Ephemeroptera is an important group of insects used in the bioassessment and monitoring of freshwater bodies worldwide because of their relative abundance in a wide variety of substrates and their increasing chances of detecting pollution impacts. In this study, their faunistic composition and spatiotemporal variations in density and diversity in River Orogodo (Southern Nigeria) was investigated at five ecologically distinct stations over a 12-month period. The mayfly nymph community responses to environmental variables were evaluated by means of biological measures and multivariate analysis (redundancy analysis [RDA]). Thirteen morphologically distinct taxa belonging to six families were identified. The dominant taxa were Afrobaetodes pusillus (23.1%), Baetis sp. (13.7%), and Caenis cibaria (11.4%). The density of Ephemeroptera differed significantly (p < 0.05) both in space and time. Diversity was influenced by substrate heterogeneity which in turn was influenced by catchment processes such as flooding and anthropogenic activities especially abattoir effluent. Based on the RDA ordination and relative abundance data, Baetis sp. dominated at impacted stations while a more equitable distribution of species were observed in less disturbed sites. Water velocity, canopy cover, nature of bottom sediments, and the amount of dissolved oxygen also accounted for the variations in Ephemeroptera densities at the different stations. Shannon diversity, taxa richness, and evenness were lowest in station 3 (the abattoir discharge site).
蜉蝣目是一类重要的昆虫，由于其在各种基质中相对丰富，并且越来越有机会检测到污染的影响，因此被广泛用于全球淡水水体的生物评估和监测。本研究在 12 个月的时间内，在五个生态特征明显的站点调查了奥罗戈多河（尼日利亚南部）蜉蝣目昆虫的区系组成、密度和多样性的时空变化。通过生物措施和多元分析（冗余分析 [RDA]）评估了蜉蝣若虫对环境变量的群落响应。鉴定出 13 种形态上不同的类群，属于 6 科。优势类群为 Afrobaetodes pusillus（23.1%）、Baetis sp.（13.7%）和 Caenis cibaria（11.4%）。蜉蝣目密度在空间和时间上均有显著差异（p<0.05）。多样性受基质异质性的影响，而基质异质性又受到集水区过程（如洪水和人为活动，特别是屠宰场废水）的影响。根据 RDA 排序和相对丰度数据，Baetis sp.在受影响的站点占主导地位，而在受干扰较小的站点观察到物种分布更为均衡。水速、冠层覆盖、底质性质和溶解氧含量也解释了不同站点蜉蝣目密度的变化。Shannon 多样性、分类丰富度和均匀度在 3 号站（屠宰场排放口）最低。
