Impact of Impoundment on the Hydrology and Rotifers of the Ikpoba River, Nigeria

Abstract

An ecological study of the Ikpoba river was carried out to evaluate the impact of impoundment on the rotifer community and water quality.  Three stations, 1, 2 and 3 were selected from upstream of the impoundment, the impoundment (reservoir) and its downstream respectively.  Among the physical and chemical parameters studied, only the water level, transparency, current velocity and dissolved oxygen were significantly different (P<0.05) among the study stations.  Fifty rotifer species were collected from the study stretch of which 30, 42 and 18 species occurred at stations 1, 2 and 3 respectively.  The families Lecanidae (33.5%) and Brachionidae (15%) were dominant in all the stations.  The overall abundance of rotifers at the three stations did not differ significantly (P > 0.05).  However, impoundment caused a significant increase in the diversity of rotifers in station 2 and a significant reduction in the downstream station 3.  Faunal comparisons of the three stations using Jaccard’s similarity index showed that stations 1 and 2 were similar, but significantly dissimilar from station 3, confirming significant community changes in the downstream lotic station