This book gives an idea about the impact of the climate changes and anthropogenic disturbances on the diversity of the marine flora. El Arish coast represented important part of Mediterranean Sea (northern of Sinai, Egypt). Climate changes attributed directly or indirectly to human activities as El-Arish power plant and El-Arish harbor in this area. The analyses by satellite from NOAA-AVHRR images between the year 2000 and 2010 revealed to erosion and accretion patterns along the coast. Therefore, the currently observed decrease in marine algal species and reduced their biomass. Spatial and temporal patterns in the distribution and abundance of macroalgae were measured. The similarity matrix showed a significant difference between the flora in 2010 and that recorded in 2000, indicating poor similarity and changes in species composition. Phytoplankton community showed in greatest abundances in winter, spring and autumn except in the anthropogenic areas as the outlet of El-Arish power plant. This coincided with different physicochemical conditions which may influence the levels and spatial patterns of phytoplankton.