The extensive invasion of algal blooms to the aquatic ecosystems at North Delta region of Egypt is a common phenomenon, and its occurrence is a function of the environmental conditions and the resource requirements of the algae; but, which, species dominates this depends on the interaction between the organism and its habitat. There is no doubt that the multiple interacting physical, chemical and biotic characteristics of an aquatic ecosystem play an important role in influencing the production and distribution of its communities. Accordingly, changes in these characteristics lead to qualitative and quantitative changes in the planktonic composition. Despite the severe problem caused by algal blooms, the phenomenon has received limited attention at this region. Nevertheless, the massive growth of algae can be viewed upon as a natural economic resource rather than a harmful impact. The present study was carried out to investigate the factors, favoring development of algal blooms and also to take advantage of the probable benefits afforded by this phenomenon.