Biodiversity Assessment of the Ancient Submerged Port of Egnazia (Southern Adriatic Sea, Mediterranean Sea): New Evidence for Conservation

In addition to their historical relevance, underwater sites of cultural heritage (e.g., shipwrecks, archeological sites) represent secondary habitats for marine life. However, despite a growing interest in their ecological role, studies focusing on these artificial environments remain limited. In this study, we performed the first systematic assessment of the marine biodiversity associated with the submerged structures of the ancient roman port of Egnazia. In particular, we conducted a seasonal (summer 2022 and winter 2023) comparative analysis of the qualitative and quantitative variations in the observed nektonic and benthic taxa between the submerged piers and two surrounding control areas. For benthopelagic and vagile benthic taxa, two seasonal samplings with four transects (of 10 m x 4 m) and three replicates per transect were conducted to analyze taxon diversity, abundance, and variability of individual size. The photo-quadrat method was employed to characterize sessile benthic taxa, using PVC frames measuring 40 cm x 40 cm, randomly placed on the study substrates with 20 replicates for each pier and the two controls. Our results highlight the occurrence of 75 taxa (67 associated with the submerged piers and 63 with the surrounding control areas), including 17 benthopelagic species, 26 vagile benthic and 32 sessile benthic taxa. Overall, our findings highlight that the submerged ancient structures of Egnazia represent a stable and functional marine habitat, promoting an increase in the local biodiversity and abundance of individuals of different species.