Ecological Quality Status of Algerian West Coast by Using Brown Marine Macroalgae Dictyota dichotoma (Southern Mediterranean Sea)

This study presents a floristic inventory of Dictyota dichotoma, a common brown alga belonging to the family Dictyotaceae, with a focus on its diversity, abundance, and distribution. Field surveys were conducted at thirteen stations along the Algerian west coast, with sampling carried out in the intertidal zone from March to April 2025. Ecological indices (Shannon diversity H′, species richness, and Pielou evenness) revealed pronounced spatial variability among stations. The highest ecological quality was recorded at Canastel (H′ = 2.86; Richness = 20; Evenness = 0.96), reflecting a diverse and well-balanced community under favorable environmental conditions. In contrast, the lowest ecological quality was observed at Ghazaouet (H′ = 2.43; Richness = 13; Evenness = 0.95), indicating reduced species diversity and suggesting potential environmental stress. The ranking analysis of D. dichotoma occurrence across the 13 sampling stations further revealed marked spatial heterogeneity. The species reached its highest recorded frequency (85.71%) at five stations—Port Say, El Marsa, Ain Brahim, Pointe de l’Aiguille, and Beni Saf—indicating the presence of favorable environmental conditions in these areas. Such elevated occurrences may be linked to optimal substrate availability, hydrodynamic exposure, and nutrient fluxes, factors known to strongly influence the growth and distribution of Dictyotaceae.