Vertical distribution of Rotifera in the Ikpoba Reservoir in southern Nigeria.

Abstract

Biweekly water and plankton samples were collected at three stations for six months between February and June 1992 along a longitudinal axis of the Ikpoba Reservoir. At each point samples were collected vertically at intervals of 1m from surface. No physical and chemical parameters apart from temperature varied with depth. The waters were of low alkalinity and conductivity. The hydrogen-ion concentration (pH) were acidic (pH 5.5-6.5) during the dry season months of February and March which tended towards neutrality (6.9 –7.2) during the rains and later to basic ( 8.0 –10.0). The waters were also under-saturated with dissolved oxygen (10% -37%) with a near anoxic condition (10%) recorded in the bottom waters. In distribution, rotifers were found at all depth, however, the pattern of distribution varied in each station. The distribution of rotifers were not affected by the physical and chemical parameters.

Key Words: Rotifers, abundance, seasonality, water quality, dam.

Tropical Freshwater Biology 11 (2002) 69-89