Mouga, Teresa2025-05-192025-05-192025http://hdl.handle.net/10400.8/12914Portugal’s rich marine biodiversity, home to approximately 550 seaweed species, is distributed across biogeographical regions influenced by Atlantic and Mediterranean climates. Human-induced stressors, including habitat degradation, pollution, and climate change, have impacted seaweed ecosystems, changed the distribution patterns and promoting the invasion of alien species. This paper evaluates the ecological dynamics of seaweed communities on the rocky coast of Abalo Beach, Portugal, using the Marine Macroalgae Assessment Tool (MarMAT) in 2022 and 2023. The MarMAT methodology, endorsed by the Portuguese Environment Agency, assesses the ecological quality of coastal areas based on taxonomic composition, diversity, and biomass of macroalgae. The assessment revealed different percentages of late-successional species (ESGI) and annual (ESGII) seaweeds, indicating a subtle decrease in late-successional species. Of concern is the increase in invasive species from one in 2009 to six in 2023, suggesting a potential threat to ecosystem integrity. Comparative analysis with previous studies confirms the ongoing ecolog ical quality and resilience of Abalo Beach. The article underscores the importance of continuous monitoring amid environmental changes and the rise of invasive species.engMarMAT indexSeaweedsSpecies richnessBiodiversity assessmentWater framework directivebook part2025-05-10cv-prod-4488158