Celestino Ladu, J.,L., Lukaw,Y.S. And Kenyi, D.D
Abstract:
This study attempt to envisage the effects of water temperature, pH and availability of nitrogen and phosphorus on the phytoplankton Melosira in Jebel Aulia Reservoir in Khartoum, Sudan. The study took a complete year from January 2003-December 2003 during which selected physicochemical variables such as water temperature, pH, nitrate and phosphate concentrations were measured at the time of plankton collection. The effects of the four physicochemical variables on the Melosira abundance were predicted by the development of seven models using the Multiple Regression Analysis of STATVIEW 5.0. The annual means of water temperature, pH, nitrate, phosphate and the Melosira abundance were in the order of 25.19 ±1.10o C, 7.99± 0.30 μgl-l, 3858.50 ±1087.37 μgl-1 and 340.83 ±12.44 μgl-1 and 1650.99±2386.90 cell L-1. The highest Melosira density of 9111.5 cells L-1 occurred in March at the temperature of 21.8o C, pH 8μgl-l, nitrate and phosphate concentrations of 3800 and 280 μgl-1. The
lowest density of 442 cells L-1 occurred in June at the temperature of 28.8o C, pH 7.60μgl-l and at the nitrate and phosphate concentrations of 4100 and 360μgl-1. The actual population density and the population density of Melosira predicted by the estimated regression model were compared using t-Test analysis and the result indicated a non-significant difference at P ≤ 0.05 (t-Value = 0.26, DF=11, P-Value =0.80) between the means of the two.
Keywords: Multiple Regression model; physico-chemical variables; Melosira; t-Test