A widespread and diversified mesophotic system of carbonate bioconstructions along the Southern Adriatic and Ionian Italian coasts is described, providing new data on the distribution, structure and associated megabenthic assemblages of mesophotic Mediterranean bioconstructions. The bioconstructions were detected at six different sites off the coasts of Apulia, in presence of marked morphological escarpments, developing on a basal substrate consisting of meso-Cenozoic carbonate rocks. Two biogenic structure types were observed, one mainly built by the nonsymbiotic scleractinians Phyllangia americana mouchezii and Polycyathus muellerae, at depths between approximately 35 and 55 m, and the other by the oyster Neopycnodonte cochlear, at depths from approximately 40 to 70 m. A total of 52 taxa of megabenthic invertebrates, belonging to 6 phyla, were found on the surface of the mesophotic bioconstructions, thus confirming the role of biodiversity hotspots of these carbonate structures. Megabenthic assemblages showed a remarkable heterogeneity both in pattern of species and abundance, probably depending on both the morphological differences of the seabed and the life traits of the single species. Primary bioconstructors seemed to influence the associated community pattern. This peculiar system deserves sound conservation measures in the light of the holistic ecosystem approach for the management of coastal marine areas.

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Coralligenous bioconstructions are one of the Mediterranean’s most distinctive and biodiverse marine habitats. This research aimed to provide a preliminary characterization of macrobenthic coralligenous assemblages at four sites located in the Marine National Park of Karaburun-Sazan in Albania. We analyzed images obtained from videos recorded along underwater transects at two different depths. Over a total of 61 taxa (3 Rhodophyta, 2 Ochrophyta, 6 Chlorophyta, 30 Porifera, 5 Cnidaria, 3 Mollusca, 2 Annelida, 1 Arthropoda, 4 Bryozoa, 4 Echinodermata, and 1 Chordata), 53 were identified at the species level using taxonomic and semi-quantitative video image analysis, thus allowing an update to the Albanian coralligenous species list with 34 new species. This study revealed differences in species richness and composition among the investigated sites and between depths, with a high number of taxa exclusive to one site and a few taxa common to all sites. Seven taxa are protected by law, among which are the echinoderm Centrostephanus longispinus, included in the Bern (Annex II) and Barcelona (Annex II) Conventions and Habitat Directive (92/43 EEC) (Annex IV), and the sponges Spongia (Spongia) officinalis and S. (S.) lamella, included in Annex III of the Bern Convention. Only the alga Caulerpa cylindracea can be considered an alien species. Although preliminary, the present research indicated the occurrence of rich and diversified macrobenthic assemblages in the study area. Moreover, it has been demonstrated that video analysis can provide a biodiversity baseline within MPAs, where traditional methods involving invasive sampling cannot be applied, particularly in areas such as the Albanian coasts, where anthropogenic impacts have been historically significant. Finally, this work provides a first estimate of the structural biodiversity in a recently established marine protected area, thus representing the basis for subsequent monitoring.