Environmental Gradients Shape Taxonomic and Functional Diversity of Intertidal Benthic Communities in the Gulf of Gabès (Central Mediterranean Sea)

Intertidal habitats of the Gulf of Gabès (central Mediterranean Sea) represent biodiversity hotspots and provide valuable model systems for investigating the diversity, structure, and ecological functioning of benthic communities.

This study investigated large-scale patterns of benthic diversity, community structure, functional diversity, and their environmental drivers across 14 intertidal flats surveyed seasonally from October 2023 to July 2024. In total, 202,102 individuals representing 184 species from 84 families were identified. Crustaceans (48%) and polychaetes (36%) were the dominant taxonomic groups, followed by molluscs and other benthic invertebrates. Species richness and abundance exhibited marked seasonal variability, with maximum values recorded during spring and summer. Multivariate analyses revealed significant spatial differences among intertidal flats, separating seagrass meadows from unvegetated muddy and sandy habitats. Functional trait analyses showed that motile surface deposit-feeders and grazers dominated vegetated areas, whereas opportunistic and tolerant taxa were more abundant in organically enriched muddy sediments.

Environmental variables, particularly sediment grain size, organic matter content, and vegetation cover, were identified as the principal drivers of community structure and functional composition. Seagrass meadows supported the highest taxonomic richness, functional diversity, and ecological quality, highlighting their role as biodiversity refugia within the Gulf. Conversely, intertidal flats exposed to stronger anthropogenic pressures exhibited reduced diversity and greater dominance of disturbance-tolerant species.

These findings provide new insights into the biodiversity and ecological functioning of Mediterranean intertidal ecosystems and emphasize the importance of conserving seagrass habitats to enhance ecosystem resilience under increasing anthropogenic pressures and climate change.