effect of anionic detergents on the standing crop of phytoplankton in El-Mex bay, Egypt

ABSTRACT

El-Mex Bay is a shallow estuary, lying west of Alexandria at longitude 29 degree sign 50E and latitude 31 degree sign 10 N. Its total area is about 20 km, and the water depth fluctuates between 1.5 and 15 meters. The bay receives large amounts of drainage water contaminated with sewage and industrial wastes from Umum Drain, which averages about 6.53 million ubi.c meter per day. The annual average standing crop of phytoplankton at the surface water and near bottom layer reached 96,560 and 25,980 units/L respectively. Chlorophytes constituted about 54.7% of the total phytoplankton in the bay [average 33.805 cells/L] They were dominated by the genera Scenedesmus, Closterium and Chlorella. Diatoms ranked as the second important class with about 24.3% of the total phytoplankton [average 15,015 cells/L]. Euglenophytes [Euglena spp] appeared less frequent, while dinoflagellates and cyanophytes persisted as rare forms. The concentration of anionic detergents in the bay water ranged between 0.0 and 1.7 mg eq. LAS/L. About 98% of the samples analysed contained less than 0.8 mg eq. LAS/L of these detergents. Regarding the seasonal variations the surface water showed an outstanding peak of phytoplankton [257,630 units/L] during spring and it consisted mostly of green algae. This was accompanied by low concentration of detergents. Lower counts of phytoplankton were recorded in the other seasons. The same seasonal cycle was observed at the bottom water but with lower counts. The sharp drop of phytoplankton counts recorded in the summer was accompanied by rapid increase of detergent concentration to an average value of 0.64 mg eq. LAS/L. Such high concentrations of detergents beside theother environmental conditions prevailing the summer season, were the main factors negatively affecting phytoplankton production. The correlation coefficients between anionic detergents and total phytop lank ton, as well as between detergents and the | different classes of ph./tu plankton. were calculated. A positive correlation between both anionic detergents and phytoplan ton during spring was proved where r= 0.78. Also high positive correlations existed between both anionic detergents and diatoms in winter [r= 0.81] and spring [r= 0.83]. Green algae gave a good correlation during spring, summer and autumn [r= 0.81, 0.83 and 0.92 respectively] while blue green algae showed good correlations during spring [r= 0.87] and summer[r=0.7 It is concluded that anionic detergent concentrations recorded In El-Mex Bay are still not toxic to phytoplankton production