Surface phytoplankton samples were collected at eight sites along certain Egyptian coasts of the Red Sea located at the southern of Sinai Peninsula and the two gulfs (Gulf of Suez and Gulf of Aqaba). Qualitative and quantitative
estimation of phytoplankton species were conducted seasonally during the period from autumn 2007 to summer 2008. The phytoplankton population was fairly diversified (181 species) comprised mainly two groups; dinoflagellates
(116 species) and diatoms (60 species). The dominant genera, in terms of the number of species, were Ceratium, Protoperidinium, Dinophysis and Gonyaulax for dinoflagellates, while Chaetoceros, Rhizosolenia and Nitzschia for diatoms.
The phytoplankton standing crop was relatively low with and average seasonal density of 1.4-7.7×103 individual/l, reflecting the oligotrophic conditions of this area. The phytoplankton abundance showed one peak in summer when
Hemiaulus hauckii (9×103 individual/l) from diatoms and Trichodesmium spp. (3×103 individual/l) from blue-green algae comprised the main bulk of the phytoplankton standing crop. Relatively high production of different species
appeared at different sites during specific season, such as Nitzschia closterium,Pseudo-nitzschia delicatissima, Rhizosolenia alata and R. calcar-avis. On the other hand, there were relatively low variations in phytoplankton composition the along study area. Spatial distribution of phytoplankton showed that Gulf of
Suez differes in the dominant species and timing of abundance from both Gulf of
Aqaba and the southern sites of Sinai Peninsula.