Phytoplankton Species Composition and Seasonal Variation at Wadi Al-Arab Dam Lake, Jordan

The composition of phytoplankton species thriving in Wadi Al-Arab Dam Reservoir, Jordan and their seasonal variation in relation to water ecology were studied between February 2001 and February 2002. A total of 75 species of phytoplankton were identified: Bacillariophyceae (diatoms) contributed with the highest number of taxa (39) followed by Chlorophyceae (23),Cyanophyceae (9), and Dinophyceae (4). Diatoms constituted 52% of the total phytoplankton flora of the reservoir and the most common species were Synedra ulna, Cymbella affinis, and Cyclotella meneghiniana with pennate and centric diatoms being the dominant species in May and October-November, respectively. Although Chlorophytes occurred most of the year, they contributed with less species to the total flora. During the summer, their occurrence was considerably reduced with dominant species of Pediastrum, Scenedesmus, and Cosmarium. Cyanophyceae dominated the phytoplankton population in summer and maintained high biomass. Dinophyceae was by far the most important group with Peridinium sp. as the most significant species thriving in the reservoir. Peridinium sp., Peridinium cinctum, with Ceratium hirundinella, and Gymnodinium sp. appeared occasionally in low numbers