Ecological study was carried out on the four closed Lakes Located at Wadi-El-Natroun. Behera Governorate. Water samples were collected during the four seasons of a year. Physical properties of water in the four lakes were measured in situ, while the other chemical and phytoplanktons determinations of the four lakes were carried out at N.R.C. Considering the chemical properties of the four lakes under study: pH was alkaline. Alkalinity was different for the different seasons in the four Lakes; the volume of water body never dries up in Humra and Gaar Lakes while dried completely in El Beida Lake at summer season. The nitrogen forms in water of these closed lakes were relatively higher, as ammonia and nitrate was high reached maximum in EI-Khadra and El Gaar Lakes. The obtained results showed that the highest total count of phytoplankton was found in El­Khadra Lake., followed by EI-Oida lake then EI-Gaar lake, and it was higher in the winter and autumn. Diatoms were the dominant phytoplanktons in El-Gaar and El-Oida Lake, while blue­green-algae were dominant in El-Khadra Lake. The N₂-fixing blue green alga Spirulina sp. was dominant in El-Khadra closed lake, with high tolerance to salt stress, as well as high content of crude protein and low content of heavy metals. This organism can be recommended to be used as a good biofertilizer for virgin sandy soil, during its reclamation.