EFFECTS OF WATER HYACINTH, Eichhornia crassipes (Laubach, 1883) ON THE DIVERSITY OF THE ROTIFER FAUNA IN OVIA RIVER, EDO STATE, NIGERIA.

ABSTRACT 

Water hyacinth (Eichhornia crassipes) is a dominant aquatic macrophyte found in tropical rivers, which has a relationship with the food web, and surrounding environment. This study aimed to investigate the influence of Eichhornia crassipes on the seasonal abundance and distribution of members of the phylum Rotifera in Ovia River, Edo State. Four stations of the river were selected along the river, and samples were collected monthly from April to September, 2019. Quantitative samples were collected at the infested station, filtered, and identified to document the results. A total of 6 rotifer species were identified, which comprised of 23 individuals belonging to 4 families, all in the Order Plioma. Testudinella patina was the most abundant species (35%), followed by Asplanchnopus hyalinus, (18%), and Trochocerca elongata (17%). The Testudinellidae family was the most dominant, found in stations 2a and 2b. Diversity indices revealed that taxa richness, abundance, and Shannon Weiner’s index were highest at station 2, the water hyacinth infested station. Taxa richness and abundance were found to be higher in the littoral zone than the limnetic zone, although not significantly different (P>0.05). There rotifer populations showed seasonal fluctuations, with no species found during the dry season. Taxa richness and abundance positively correlated with water level, water velocity, chloride, nitrate and heavy metals. Factors which influenced the abundance and distribution of zooplankton included; the nature of the water body, habitat richness and stability, anthropogenic activities, trophic conditions, resource partitioning, and predation. Conclusively, it was established that water hyacinth plays an active role in influencing the rotifer community in their microhabitats. This study provides valuable information for the management and conservation of aquatic ecosystems.