An Evaluation of the Influence of Physico-Chemical Parameters on the Abundance of Benthic Macro- Invertebrates of a Perennial Tributary Stream in Southern Nigeria

This study is the first to investigate the influence of physico-chemical parameters on the benthic macro-invertebrates of the perennial tributary stream, Ikpa River in Southern Nigeria, provid ing a preliminary baseline on the composition, abu n- dance and seasonal variation of the benthic fauna. Water quality parameters and benthic fauna were sampled monthly fro m May - December, 2010 at three stations to determine the current physical and chemical qualities of the river and to evaluate their influence on the abundance of the benthic macro -invertebrates. A mong the physical and chemical parameters studied, only water temperature, flow velocity, TDS and conductivity were significantly different (P 0.05), but there was significant d ifference between stations 1 and 3 (P<0.05), and stations 2 and 3 (P<0.01). The do minant groups of fauna were Diptera and Annelida. The dipteran family, Chironomidae was the most dominant in terms of fauna a b- undance. Conductivity accounted greatly for the significant differences observed in species general diversity indices between station 3 and station 1 and 2 wh ich were not significantly d ifferent, since Duncan's mu ltiple range tests indicated that station 3 which is tidal was responsible for the significant differences in conductivity among the stations. Only alkalinity correlated sig- nificantly (P<0.01) with the benthic macro-invertebrates at station 3.