Ecological study on seaweed diversity in Suez, Hurghada and Marsa Alam, Red Sea, Egypt.

Seaweed vegetation is widely distributed along the Red Sea coasts. Therefore, the current study presents an ecological study on the spatial and temporal variations of seaweed vegetation at three different sites (Suez, Hurghada and Marsa Alam) along the western coast of the northern Red Sea. The study was conducted through regular seasonal visits over four seasons, starting from winter 2022. Physicochemical parameters were measured, and the coverage of seaweed species was estimated using the quadrat method. Forty-seven species of seaweeds were collected and identified from the studied sites during the study period. Site II (Hurghada) had the highest number of species (n = 37), whereas site I (Suez) had the lowest (n = 11). The findings reveal significant variations in species composition, and coverage, highlighting the influence of environmental factors and seasonal changes on seaweed communities. Site I (Suez) recorded the highest average percentage cover of Chlorophyta (97%), where Phaeophyceae (50%) and Rhodophyta (38%) recorded the maximum at site II and site III (Marsa Alam), respectively. In general, winter and spring recorded the highest number of species (43 and 38, respectively), while autumn recorded the lowest (n = 33). In spring, Chlorophyta recorded the highest coverage (35.7%) mostly represented by Ulva lactuca, Caulerpa racemosa, Dictyosphaeria cavernosa, Valonia aegagropila and Cladophora prolifera, followed by Rhodophyta (34.3%) with a dominance of Actinotrichia fragilis and Jania rubens. Furthermore, regular biodiversity monitoring is necessary to continuously update the species and detect any changes that may occur in the physicochemical and biological parameters of the ecosystem, including the effects of climate change.