RESUMO
The hydrographic, phytoplankton and bacteria data were collected monthly during 1995 from nine selected beaches of Alexandria, as an attempt to classify Alexandria recreational areas. The results showed a distinct difference between the water quality of Eastern and western parts of beaches in all parameters. Generally, relatively high values of water salinity, low concentration of nutrient salts particularly ammonia, nitrite and silicate as well as low oxidizable organic matter are considered as indicators of improvement in the water quality. The phytoplankton standing crop displayed wide variation, from 9 x 103 to 20.5 x 106 unit.L-1 chlorophyll-a content from 0.01 to 12.7 mg.m-3, Coliform bacteria from 0.0 to 2600 per 100 ml and diversity from 0.09 nats to 2.57 nats. The phytoplankton comprised 102 taxa belonging to a wide ecological habitat, extending from fresh water forms [33 species] to typical marine forms [69 species] often found side by side. However, few of them were responsible for the bulk of the community; namely, Skeletonema costatum, Rhizosolenia fragilissima, R. delicatula, R. hebetata, Nitzschia seriata, Chaetoceros socialis and Euglena granulata. The highest distribution of phytoplankton standing crop, chlorophyll-a and bacteria counts as well as low diversity values were recorded at a highly eutrophic area, Shatby and Anfoushi beaches. Monthly variation showed the highest outstanding peak in summer months. Several phytoplankton species were recorded as indicators of eutrophication. The correlation between phytoplankton standing crop, chlorophyll-a content, diversity, bacteria counts and the environmental conditions at each beach were computed and discussed