Salinity and the Macrobenthic Community Structure in Eichhornia crassipes of Warri River, Nigeria

The Macrobenthic community assemblage associated with Eichhornia crassipes (water hyacinths) was investigated at two sampling stations of Warri River. One hundred and twelve species of benthic organisms in forty-one families were identified. All except mollusca group are well known freshwater forms which are limited in longitudinal distribution to areas with salinity below 1.02%. Ephemeroptera, Coleoptera, Trichoptera and Arachnida were restricted to the freshwater areas (upstream station 1) with salinity values of 0.02-0.46%. Dominant groups are Oligochaeta (Naididae), Ephemeroptera (Baetidae) and Diptera (Chironomidae) with 13, 10 and 9 taxa, respectively. In this respect, they are considered to be the most sensitive groups in water hyacinths to salinity gradation in Warri River. Therefore they serve as very useful bioindicators of environmental change including human-induced stress factors in aquatic ecosystem.