Comparison of the impacts of climate change and anthropogenic disturbances on the El Arish coast and seaweed vegetation after ten years in 2010, North Sinai, Egypt

Human activities on coasts and climate changes during the past ten years have given rise to considerable shoreline changes along the El Arish coast (the northern coast of the Sinai Peninsula). In the El Arish Power Plant, sediment accretion has reached the tip of the breakwater of the cooling water intake basin, necessitating extensive dredging inside the basin. To the east of El Arish Harbour, the shoreline has been in continuous retreat. The differences between the year 2000 and 2010 in the shoreline along the El Arish coast were determined by analysing satellite images from NOAA-AVHRR images. The analyses revealed erosion and accretion patterns along the coast. The physical parameters showed that the minimum water temperature of 18°C was recorded at site I in winter and that the maximum was 40°C at site II in summer. The latter temperature can be attributed to the effluent discharge of cooling water from the El Arish power plant. Spatial and temporal patterns in the distribution and abundance of macroalgae were measured at four sites (I, II, III and IV) along the El Arish coast. The percentage cover of the successional macroalgae exhibited environmental fluctuations. After ten years, the phytocommunity showed that red and green algae were dominant at the study sites. Significant differences between past and current flora were observed. 39 taxa recorded in 2000 were absent in 2010, while 9 taxa not previously reported were present in 2010. These changes are discussed in the context of possible global warming effects. PERMANOVA showed significant changes (p < 0.001) between sites, seasons, species abundance and macroalgal groups along the El Arish coast in 2000 and 2010. 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 among the seasons at the different sites. Most of the algae belonged to the filamentous, coarsely branched and sheet functional form groups.