Macroinvertebrate Community and Pollution Tolerance Index in Edion and Omodo Rivers in Derived Savannah Wetlands in Southern Nigeria

We carried out a study of the macroinvertebrates community and pollution tolerance index (PTI) in Edion and Omodo Rivers in Agbede wetlands for eight months (from March to October, 2010). Two stations, upstream and downstream, were chosen for each river. Benthic fauna was sampled fortnightly, using the modified Ekman Grab designed for shallow waters. Eight major taxonomic groups comprising 33 taxa were collected in this study. The dominant groups by percentage density occurrence were Ephemeroptera (45.4 %) > D iptera (24.7 %) > Decapoda (24.03 %). The number of taxa was least for station 2 (14) and was highest (23) for station 4, with highest population density recorded for station 1 (211 individuals). The heterogeneity indices revealed higher values for evenness across the stations except, for station 1 (0.3574). Meanwhile, PTI values showed moderate water quality with range of values from 7 to 16.