ABSTRACT

The effect of water hyacinth, Eichhornia crassipes (Pontederiaceae) on zooplankton biodiversity particularly copepod is less well understood. The effects of water hyacinth infestation on the diversity, abundance and composition of copepod species in Ovia River, Edo state Nigeria were investigated.Quantitative copepod samples were collected from four selected sites, comprising site without and with water hyacinth mat (litorral and limnetic point) monthly for a period of 6 months, April to September, 2019 (dry and wet season).The species composition of the copepod recorded from the sampled sites comprises one family, 8 species and 70 individuals. Thermocyclops neglectus and Thermocyclops oithonoides represented the most dominant species (47% and 11% of copepod community respectively).   The water hyacinth infested station recorded a total of 55 individuals, while the stations without water hyacinth had a total of 15 individuals. Also, taxa richness, Shannon weiners and simpson indices were higher in the station with aquatic macrophyte than stations without macrophyte. In station 2, taxa richness and abundance were found to be higher in the littoral zone, than the limnetic zone though not significantly different (P>0.05). There was seasonal variation in the copepod populations, as they were encountered only during the wet season, and no species was found during dry season.Taxa richness and abundance established positively strong correlation with water level, water velocity, transparency, chloride, BOD₅, nitrate and heavy metals. This result suggests that the presence of water hyacinth had positive impact on the copepod biodiversity in the study area.