Spatial and Temporal Variations in Macroalgal Biodiversity on the Intertidal Rocky Shores of the Doukkala Coast (Atlantic Morocco)

Morocco, bordered by the Atlantic Ocean and the Mediterranean Sea, is recognized as a country of high biodiversity, particularly rich in marine flora such as macroalgae. These organisms are widely distributed along the coasts and play a fundamental role in maintaining the ecological balance of coastal marine ecosystems. This study aims to assess the spatial and temporal variability of macroalgal diversity along the Doukkala coast (Atlantic Morocco), a region known for its ecological and economic importance. From January to December 2019, monthly surveys were conducted in the intertidal zone across selected sites. The investigation focused on species composition, functional groups, and percentage cover in relation to seasonal fluctuations in key physicochemical parameters, including temperature, salinity, pH, nitrate (NO₃⁻), orthophosphate (PO₄³⁻), and dissolved oxygen. Ecological index analysis and principal component analysis (PCA) were also performed to assess the relationships between macroalgal diversity and environmental factors. A total of 206 macroalgal species were identified, including 151 Rhodophyta, 29 Phaeophyta, and 26 Chlorophyta. Seasonal trends indicated a notable increase in species richness during the spring. The diversity and distribution of macroalgae along the Doukkala coast were strongly influenced by both physical factors (temperature, salinity) and chemical parameters (nitrate, orthophosphate, and dissolved oxygen). this study highlights the dynamic response of macroalgal communities to environmental variability, offering essential insights into the ecological status and resilience of marine ecosystems along the Atlantic coast of Doukkala.