A study of physico-chemical water quality and caddisfly larvae abundance in Opa Reservoir Stream, South-Western Nigeria

Abstract

This research was carried out at Opa Reservoir Stream in Ile-Ife, Nigeria, between 2004-2005. The study investigated the physico-chemical water quality and abundance of caddisfly larvae in the stream. The larvae were found to be unprecedentedly abundant when compared with other aquatic insects inhabiting the three stations selected at the stream. Hence the study focused on physicochemical parameters of the stream in relation to the abundance of caddisfly larvae. The sampling stations (Stations A, B and C) selected were based on the streambed morphology. Water samples were collected and analysed to determine the physicochemical characteristic of the stream. Samples of larvae were also collected and identified to the lowest taxonomic level. Only two species of caddisfly in different biotopes occurred at the three stations; Cheumatopsyche digitata larvae were found at Station A and Macrostemum alienum larvae inhabit both stations B and C. Data collected were analysed using relevant inferential statistics which include descriptive statistics and Pearson correlation coefficient. There was fairly high positive non-significant relationship between DO and abundance of C. digitata (r = 0.55) in Station A, while in Stations B and C, there was a positive significant relationship between DO and M. alienum larvae. This implies that the high concentration of DO favours the abundance of M. alienum than C. digittata larvae, which implies that C. digitata tolerate lower DO concentration than M. alienum. There was negative non-significant correlation between the two species at the three stations and chloride ion in the stream which suggest that the caddisfly species is not favourly disposed to high concentration of chloride ion at the stream. In conclusion since the stream accommodate caddisfly species which have low tolerant level for pollution, it is can therefore inferred as uncontaminated water.