Ahmed M. El-Otify
Department of Botany, Faculty of Science, Aswan University, Aswan 81528, Egypt.
The position of fish hatcheries in an extreme arid area may indicate that they acquire specific environmental conditions. The purpose of this work is to describe the main features of the fish ponds phytoplankton population in relation to their ecological status. Attention is paid to phytoplankton quantity and quality as well as to changes in phytoplankton assemblages caused by alterations of environmental features. Investigations of the hydrobiological conditions of aquaculture's phytoplankton that were carried out during the last two decades in aquacultures of the Nile tilapia; Oreochromis niloticus (L., 1758) and the grass carp; Ctenophryngodon idella (Val., 1844) were followed as a case study. The phytoplankton population dynamics are expected as a consequence of the impact of combination of different biotic and abiotic elements. The phytoplankton development may reflect the ecological status of fishponds. Due to occasional man-made manuring, irregular variations in the availability of macronutrients could influence the qualitative and quantitative composition of the phytoplankton community. The feasibility of phytoplankton monitoring as an indicator of ecological status of fish ponds, identification problems of phytoplankton and the need of a methodological tradition are considered. These investigations provide evidence on complex trajectories of aquatic ecosystem shifts driven by hydrobiological alterations in aquacultures of subtropical habitats.