This study assesses the ecosystem services provided by algae and seagrass species structuring the lagoonal ecosystems along the Moroccan Atlantic coast, with a focus on the Oualidia Lagoon. A comprehensive literature review was conducted to identify and evaluate the contributions of key native species ( Gracilaria gracilis , Ulva spp., Cystoseira humilis , Fucus spiralis , and Zostera noltei ) and the invasive species Sargassum muticum to Marine and Coastal Ecosystem Services (MCES). A semi-quantitative approach was applied to integrate the functional and spatial value of each species into the overall assessment of MCES. Results indicate that 70–85% of potential services are documented, with native species mainly contributing to regulating and supporting services, while S. muticum shows a negative impact on about 43% of them. Current exploitation remains limited, except for agar-agar extraction from Gracilaria , confirming the low use of provisioning services. Overall, 25–30% of potential services are underutilized, aligning with the Ramsar site’s emphasis on sustainable use. Promoting native algae cultivation could enhance local economic and ecological outcomes while contributing to multiple SDGs, including food security, climate action, and biodiversity conservation.