Community pattern and diversity index of macro-invertebrates in relation to Surface water interface of River Ndakotsu (latitude 90.34N and longitude 60.30E), Lapai, Nigeria was conducted from November 2010 to October 2012, using the modified kick sampling technique. Five stations were selected from upstream to downstream base on anthropogenic activities and ecological status of the River. Water quality changes indicated significant differences (p<0.05) in water and air temperatures, depth, turbidity, velocity, conductivity, pH, water hardness, total alkalinity; nitrate-Nitrogen and phosphate-phosphorus, but insignificant (p>0.05) in BOD5 and COD between the five sampled stations within the months. Higher values of these parameters were observed at the impacted station 3. The total number of taxa and individuals analyzed at stations 1, 2, 3, 4 and 5 were 8(788), 5(488), 4(120), 8(1366) and 11(1699) respectively. Comparisons of abundance values demonstrated high significance (p < 0.05) between the impacted station and the upstream (station 1) and downstream station (station 5). Station 5 had the highest species richness, evenness, and diversity; while the anthropogenic activities in station 3 altered the water chemistry as well the richness, evenness and diversity of the species. The significant role of dissolved oxygen in the abundance and diversity of macroinvertebrate is well correlated in the study, where high abundance and species divers were recorded in stations with the highest dissolved oxygen levels. The presence of Musca sobens and Culex pipiens present in station 3 (impacted station) and 2 (partially impacted) is a characteristic of polluted waters. While Biomphalaria grabrata, Lymnaea natalensis and Bullinus globosus are vectors of parasites that causes diseases.
