Impact of Environmental Conditions on the Phytoplankton Structure in Mediterranean Sea Lagoon, Lake Burullus, Egypt

Lake Burullus is one of the northern Delta lakes, connected with the Mediterranean Sea through El-Boughaz opening. The main objective of the present work is to study the physical and chemical properties of the lake and its relation with the phytoplankton communities, chlorophyll-a as well as diversity and Eutrophication index. The studies revealed that, the pH values lie in alkaline side, with wide range of fluctuation (7.15–8.5), the total suspended matter was relatively high (18.2–149 mg l^?1), high values of dissolved oxygen (5.17–11.29 ml l^?1) and high concentration of nutrient salts, (nitrate ranged between (3.4–44.7 μmole l^?1), nitrite (0.42–15.95 μmole l^?1), ammonia (1.46–50.60 μmole l^?1), phosphate (0.63–14.83 μmole l^?1), and silicate (6.54 to 119.3 μmole l^?1). Chlorophyll-a concentration showed a wide range of fluctuation (13.8–127.4 μg/l) and the highest value were recorded at the western region of the lake. Phytoplankton counts showed a pronounced increase (1.9 × 10⁶ units l^?1) as compared with previous studies, a total of 170 species were identified represented mainly by Bacillariophyceae (44.8% to the total community) comprising 68 species, Chlorophyceae (39.99%) 54 species, followed by Cyanobacteria (9.52%) 26 species, Euglenophyceae (5.63%) 15 species. Phytoplankton standing crop attained the highest counts at the western sector particularly at station X during spring and summer (6.7×106 and 4.1×10⁶ units l^?1 respectively) due to the dominance of Bacillariohycean species Stephanodiscus phytoplankton diversity was high and showed widely range (1.47–3.66 nats). A series of stepwise regression equations describing the dependence of phytoplankton standing crop, its main groups and diversity index on the changes of the most biotic prevailing conditions were given and discussed. In general, the results showed that the Lake is considered as a eutrophic area. This phenomenon observed in the body of the lake water that receives large influxes of nutrients, which reflects high phytoplankton counts, diversity index and Chlorophyll-a     

Trace Metals in the Water Columns of the Red Sea and the Gulf of Aqaba,Egypt

Seawater samples were collected from the northern Red Sea and the Gulf of Aqaba at different depths during February 1999 and analyzed for iron, zinc, manganese, nickel, copper, cadmium, cobalt and lead to determine the existing concentration of these metals, their distribution patterns and where contamination has occurred. The concentrations of Fe, Zn, Mn, Ni, Cu, Cd, Co, Pb were scatteredin the ranges: (0.56–4.44; mean 1.67±0.9 μg L^-1), (0.13–1.17; mean 0.24±0.12 μg L^-1), (0.06–0.21; mean 0.13±0.03 μg L^-1), (0.05–0.52; mean 0.16±0.06 μg L^-1), (0.07–0.29; mean 0.14±0.06 μg L^-1), (0.02–0.78; mean 0.49±0.14 μg L^-1), (0.06–0.29; mean 0.15±0.04 μg L^-1), and (0.02–0.68; mean 0.31±0.13 μg L^-1), respectively. The results revealed a small range of variation and regional irregularities. It also indicated significant higher concentrations for Fe, Cd and Pb compared to other metals. Compared to the northern Red Sea, significant higher concentrations for Ni and Cd are measured at the Gulf of Aqaba. Other metals, i.e. Fe, Zn, Mn, Cu, Co, and Pb are not significantly different in both areas indicating no distinct concentration gradients. Except for Pb, the distribution patterns indicated significantly lower concentrations at surface layer in both regions, then increasing to their maximum values at the sub-surface layers which followed by a decrease in deep water. The study indicated also that the mean concentrations of trace metals examined here are much lower than those reported for the Mediterranean Sea and typical of open ocean water.