Mapping and Characterizing Coastal Habitats and Benthic Ecosystems in Al-Wajh, Northern Red Sea

The Al-Wajh region of the northern Red Sea represents a unique and ecologically significant marine environment characterized by extensive coral reef systems, diverse benthic habitats, and distinct hydrodynamic and climatic conditions. This area, with its complex reef structures and rich biodiversity, offers critical insights into coral reef resilience and ecosystem functioning under varying environmental influences. Therefore, this study was carried out in which an in-situ survey of 30 sites across three reef sectors in the Al-Wajh region assessed habitat composition, benthic structure, coral diversity, marine invertebrates, and marine flora, revealing strong spatial heterogeneity. Sector 1 featured a complex back-reef lagoon with diverse benthic assemblages, while Sector 2 had simpler topography but the highest mean hard coral cover (49.87%). Sector 3, an offshore sandy-bottom area, showed patchy coral distribution mainly in the south, likely influenced by ocean currents; despite its lower coral cover (17.5%), it supported the highest invertebrate diversity (8.3 species per site), suggesting greater habitat complexity and lower disturbance. Soft corals and turf algae were widespread, whereas crustose coralline algae and cyanobacteria were sparse and macroalgae were absent. The coral community comprised 62 species, nearly half listed as Least Concern and about 40% as Near Threatened, including the endemics Acropora variolosa and Lobophyllia erythraea. Invertebrate assemblages were dominated by Echinometra mathaei and Diadema setosum. The algal flora showed high richness and productivity, with 94 species dominated by Rhodophyta, and five seagrass species, the most common being Thalassodendron ciliatum. Statistical analyses confirmed significant spatial differences among benthic categories and a negative correlation between hard coral cover and sand accumulation.