The Role of Abiotic Factors in Diurnal Vertical Distribution of Zooplankton in Awba Dam, Ibadan, Nigeria

Abstract

Zooplankton density at the different depths was determined. Physico-chemical parameters were related to the vertical distribution of zooplankton in the dam. Temperature, pH, dissolved Oxygen decrease with depth while alkalinity, dissolved Carbon dioxide, Nitrate contents and conductivity increase with depth.  Zooplankton density decreases with increase in the sampling depths. Two genera of Cladocera, four genera of Protozoa, four genera of Copepoda and five genera of Rotifera were identified. The highest number of zooplankton was recorded in the month of May. The study demonstrates that the differences in the vertical distribution and species diversity are directly related to the influence of lake stratification. A connection was detected between the depth and number of individuals. In this study, the average vertical position of the zooplankton ranged from less than one metre to  more than 3 metres, and relationships to environmental factors were quite variable, depending on zooplankton group and sampling date. However, for individual zooplankton groups and sampling dates, temperature and oxygen profiles also significantly influenced zooplankton vertical position.

Keywords: Zooplankton, Awba dam, physico-chemical parameters, distribution, sampling depths.