Evaluation of the physicochemical and chlorophyll-a conditions of a subtropical aquaculture in Lake Nasser area, Egypt

Water quality, nutritional characteristics and phytoplankton biomass in aquaculture of Oreochromis niloticus (L.) simultaneously with its water source supply (Lake Nasser), were monthly investigated over a one-year period (July 2009–2010). Analysis of the results showed that application of fertilizers and environmental conditions appeared to be the principal factors influencing the spatio-temporal variations of water quality and productivity. The data obtained revealed differences between the fish pond and its water supply. Monthly fluctuations in the availability of the major nutrients reflected the occasional supply of the fish pond with different nutrients. Phytoplankton biomass in terms of chlorophyll-a concentrations were always of relatively higher values in the fish pond than those in Lake Nasser's water. Elevation of pH values and dissolved oxygen saturation levels appeared concomitantly with the increase of chlorophyll-a concentrations due to the phytoplankton photosynthetic assimilation activities. The observations of the present study highlighted the chlorophyll-a concentrations as an indicator of phytoplankton biomass reflecting water quality in the Nile tilapia aquaculture ecosystem.