Phytoplankton assemblage of a solar saltern in Port Fouad, Egypt

The present study is the first investigation of the phytoplankton community in one of Egypt’s saltworks. The phytoplankton composition and distribution in five ponds of increasing salinity were investigated in the solar saltern of Port Fouad. The phytoplankton community consisted of 42 species belonging to cyanobacteria (16), diatoms (12), dinoflagellates (11), Euglenophyceae (2) and Chlorophyceae (1). The number of species decreased significantly and rapidly with increasing salinity, varying between 33 species in the first pond (P1) and one species in the crystallizer pond (P5). Conversely, the total phytoplankton density, except that recorded in P1, increased significantly with rising salinity, fluctuating between 8.7 and 56 × 105 individuals l− 1 in P2 and P5 respectively. In spite of the local variations in climate and nutrient availability, the phytoplankton composition, density and spatial variations along the salinity gradient were, in many respects, very similar to what has been observed in other solar saltworks. The pond with the lowest salinity (P1 − < 52 g l− 1) was characterized by a significant diversity and blooming of diatoms and dinoflagellates. Intermediate salinity ponds (P2 and P3) with salinity ∼ 112–180 g l− 1 exhibited a decline in both species richness and density, but the stenohaline blue green algae (Synechocystis salina) did flourish. The highly saline concentrating ponds and crystallizers (P4 and P5) with salinity ∼ 223–340 g l− 1 were characterized by few species, the disappearance of blue green algae and the thriving of the halotolerant green alga Dunaliella salina.