Some Aspects of Limnology and Plankton Population of River Ochekwu, Benue State, Nigeria

Abstract

This study examined some aspects of water quality parameters and plankton population of River Ochekwu, Benue State, Nigeria for management purpose. The physico-chemical status of water samples from three stations was investigated monthly for a period of one year. Water temperature, pH, Conductivity, Total Dissolved Solids, and Dissolved Oxygen (DO) were measured in situ with the aid of Hanna Model HI 98129 while BOD was determine using DO meter model DO-5509, Transparency was measured with Secchi Disc and Air temperature was measured with the aid of a Mercury in glass Thermometer. Total Hardness, Total Alkalinity, and Carbon Dioxide were determined titrimetrically. Planktons were collected using a 55µm plankton net and both were preserved separately in 4% formalin. Two-way ANOVA and analysis of co-variance at P<0.05 were used to analyze the result using GLM procedures of the analysis system (SAS). The results showed Air temperature range from 29.23ºC to 29.98ºC, Water temperature of 26.57ºC to 26.66ºC, Dissolved Oxygen of 4.59mg/ to 5.98mg/l, BOD of 2.76mg/l to 3.80mg/l, pH of 6.79 to 7.08, TDS of 77.06mg/l to 79.20mg/l, Transparency of 42.99 to 99mg/l, EC of 80.25µS/cm to 83.56µS/cm, Total Alkalinity of 49.87mg/l to 51.40mg/l, Total Hardness of 37.14mg/l to 46.05mg/l, and Carbon dioxide of 42.65mg/l to 46.24mg/l. Thirty three species of phytoplankton from four families were identified with Chlorophyceace dominating with 18 species followed by Cyanophyceace with 7 species, Bacillariophyceace with 6 species and Chrysophyceace with 4 species. Zooplankton composed of 23 species from three families with 12 species of Rotifera, 6 species of Cladocera and 5 species of Copepoda. The results obtained fell within the maximum permissible limit set by World Health Organization for drinking water. Variations were observed in the parameters by season and stations with plankton being abundant in the wet season.