Diversity and future perspectives of Mediterranean deep-water oyster reefs

Anthropogenic and climate factors are increasingly affecting the composition and functions of many marine biogenic reefs globally, leading to a decline in associated biodiversity and ecosystem services. Once dominant ecological component, modern oyster reefs in the Mediterranean and Black Sea and the Atlantic Ocean have already been profoundly altered by overharvesting, habitat loss and the introduction of alien species. Far less known are deep-water oyster reefs, which can however form substantial biogenic structures below 30 m depth. Here we analyze the diversity of benthic assemblages associated with deep-water oyster reefs formed by the gryphaeid Neopycnodonte cochlear, and other mesophotic habitats in the central Mediterranean Sea using a taxonomic and functional approach. Our findings suggest that deep-water oyster reefs may act as hotspots of biodiversity and ecological functions in the Mediterranean Sea under current conditions, having also an edge in survival in a changing ocean.