PHYSICO-CHEMICAL PARAMETER VARIABILITY RELATIVE TO SEASONAL DYNAMICS AND COMMUNITY STRUCTURE OF PLANKTON IN THE BOUKOURDANE LAKE DAM (ALGERIA)

The impact of seasonal variations in the water physico-chemical parameters on the zooplankton and phytoplankton composition was investigated in the Boukourdane reservoir (Tipaza, Algeria) over two years (April 2005-March 2007). High levels of nitrites were observed during the cold seasons, and the phosphate levels were higher in summer with a very high NO sub(3) super(-)/PO sub(4) super(3-) ratio (>30) in winter. A significant increase in the level of chlorophyll a (Chi a) was observed in spring. The relative standard deviations (RSDs) highlighted a large variability during the warm seasons, especially for nitrites, nitrates, phosphates and ammonia. A great species diversity was observed (rotifers: 79, copepods: 13, and phytoplankton: 83). The weighted averages of the species enabled us to determine the optimal values of their physico-chemical parameters, as elevated temperatures for Bacillariophyta and Pyrrhophyta or high concentrations of chlorophyll a for Charophyta. The zooplankton was more prevalent during the spring and appeared to be correlated with sulfates and electrical conductivity. A redundancy analysis (RDA) corroborated the previous results and explained 84.1% of the total variance. This analysis highlights the influence of some of the environmental variables on the seasonal distribution of plankton, characterized by a high profusion in spring and scarcity in autumn and winter.