ABSTRACT
Water hyacinth (Eichhornia crassipes) is an aquatic macrophyte found in tropical rivers. It is dominant in many Nigerian water bodies, and has a relationship with the environmental conditions and zooplankton. This study was carried out in order to investigate the effects of Eichhornia crassipes on the rotifers in Ovia River, Edo State. Four stations of the river were selected for sampling, from April to September, 2019. Quantitative samples collected at the infested station were fetched along with the macrophytes in a bucket, and the content was filtered. Samples were identified, and the results were documented. A total of 6 rotifer species was encountered, comprising of 23 individuals belonging to 4 families, all in the Order Plioma. Species percentage composition of the rotifers found included; 35% for Testudinella patina, 18% for Asplanchnopus hyalinus, and 17% for Trochocerca elongata respectively. The most dominant family encountered was Testudinellidae, which was found in stations 2a and 2b. Diversity indices revealed that taxa richness, abundance, and Shannon Weiners' index was highest at station 2, which was the water hyacinth infested station. In this station, taxa richness and abundance was found to be higher in the littoral zone, than the limnetic zone though not significantly different (P>0.05). There was seasonal fluctuation in the rotifer populations, as they were encountered only during the wet season, and no species was found during dry season. Taxa richness and abundance positively and strongly correlated with water level, water velocity, chloride, nitrate and heavy metals. Conclusively, it was established that water hyacinth plays an active role in influencing the rotifer community in their microhabitats.
