Investigative study on macroinvertebrates and pollution tolerance index of four rivers in the derived savannah belt of Edo-North in Southern Nigeria was carried out from January to December, 2010. The study involved monthly field sampling and laboratory analysis of macrofauna. The objectives of the study were to evaluate the biodiversity status and importantly, the environmental integrity of the four selected rivers. Two dominant macroinvertebrate families were recorded; Baetidae and

more »

... e while, 53 macroinvertebrate taxa were identified across the rivers. The highest number of species (12) was recorded for Diptera, while, Hirudinea, Nematoda and Arachnida each had 1 species in the population. General diversity indices ranged from 2.02 to 2.78 with the least and highest recorded in Edion and Etuno Rivers, respectively. The fauna evenness index indicated that the water bodies had values less than 1.0. Meanwhile, Pollution tolerance index revealed spatial and seasonal variations in water quality conditions but only Edion River exhibited poor water quality in all the months of study.