Water quality parameters and aquatic insect diversity in Aahoo stream, southwestern Nigeria

Abstract Background The role of water in the maintenance of an aquatic ecosystem is indispensable. In this study, aquatic insect biodiversity and the physico-chemical parameters of Aahoo stream, in southwestern Nigeria, were investigated from March to August 2017. Seven physico-chemical parameters were examined in six study sites. Results There were significant effects (p < 0.0001) of flow rate (F 5, 12 = 2221.9), electrical conductivity (F 5, 12 = 276.3), air temperature (F 5, 12 = 110.3), water temperature (F 5, 12 = 55.5) and pH (F 5, 12 = 31.45) on the quantity of aquatic insects at the study sites in Aahoo stream. Dissolved oxygen (F 2, 12 = 7.82) also had a significant impact (p = 0.002) on the quantity of aquatic insects at the stream. Three aquatic insect orders, Diptera (most dominant), Odonata (median dominant) and Hemiptera (least dominant)], nine families and 12 genera were found occurring in the stream. Chironomus sp. (Chronomidae, 55.29%), Brachithemis sp. and Orthetrum sp. (Libellulidae, 21.84%) which are usually associated with polluted water showed the highest occurrence in the stream. Low values of diversity indices were observed across the six study sites, which suggest that the six sites were in unstable conditions. Site 5 has the richest (Simpson 1-D 0.77, Shannon H 1.81, Margalef 1.91) and best taxa distribution (Equitability J: 0.73), while site 3 was the poorest (Simpson 1-D 0.52 and Shannon H 1.31) and the least in taxa distribution (Equitability J 0.55). Conclusion This study has provided information on the assemblage and copiousness of various aquatic insects as well as the physico-chemical parameters of Aahoo stream. It could therefore be concluded that the stream could be somewhat polluted and unsafe for human consumption without being properly treated.