Effects of Nutrient Dynamics on the Abundance of Some Zooplanktons in Wasai Reservoir in Kano, Northern-Nigeria

Abstract

The distribution, relative abundance and species diversity of some zooplanktons and the changes in nutrients composition and concentrations was studied for the period of three months in Wasai reservoir Kano, Nigeria. Protozoa, Rotifera, Cladocera and Copepoda were identified. Protozoan number was dominant over the other zooplankton group throughout the period of sampling and in all the sampling points; then followed by Rotifera, Cladocera and Copepoda was represented by few species. Total individuals of Rotifera and Cladocera observed were 236 and one hundred and thirty six respectively. Highest and least occurred Rotifera Cladocera and Rotifera were observed have 79 species and twenty-nine, while Cladocera has fifty and twenty species respectively. The reservoir was within small range of pH 7.8 to 8.5 of mild alkaline condition, PH values decrease from the sampling point I down the sampling point V. Surface water temperature variations recorded was minimal. Maximum temperature observed was 23℃, and the least was 16℃. These slight variations  resulted in a weak relationship ( r =0.398) with zooplankton Physical parameters (e.g. transparency) in this research work was fairly uniform, ranges from 0.30m to 0.35m at all the sampling points, and throughout the period of this research there was no rainfall which might increase the level of  reservoir water and its transparency. This slight variation in the water transparency among the sampling points when correlated with zooplankton counts were found to have a weak relationship (r=0.382). It has no influence on the distribution and abundance of zooplankton. The value of dissolved oxygen (DO) was observed to be increasing gently from sampling point I to V (3.7 mg/l to 4.4 mg/L), although there was sharp rise in sampling point III (4.6 mg/L). While Biochemical Oxygen Demand (BOD) decreases from sampling point I to V (2.7 to 2.4 mg/L), unlike DO, there was sharp decline in sampling point III (2.1 mg/L). The increase in dissolved oxygen and decreased in biochemical oxygen demand along the sampling point II, III, IV, V), and (I was due to nutrient enrichment from the continuous influx of sewage from the Jakara River. It revealed that highest phosphate ion concentration recorded was in sampling point I. This might be because of incoming domestic wastewater from Jakara River

Keywords: Jankara, Rotifera, Cladocera, Copepoda, , Wasai