Coastal Habitats in the Aegean Sea: Soft Bottom, Seagrasses, and Hard Bottom

The marine life on the seafloor of the Aegean Sea, from the sea surface to the edge of the continental shelf, is presented as a succession, in four bathymetric zones. The first two zones (supralittoral and mediolittoral) correspond to intertidal system, which is very narrow, due to the small range of tides in the Aegean Sea. Next to them, the other two zones (infralittoral and circalittoral) correspond to the subtidal photic system, which, in contrary, is very large due to the high transparency of the seawater. The infralittoral zone is extended down to 40 m depth, with the meadows of the endemic Mediterranean seagrass Posidonia oceanica to be the dominant habitat on soft bottoms. On rocky infralittoral bottoms, a plethora of macroalgae is present, with the brown algae of the emblematic Mediterranean taxon Cystoseira to be the dominant element of the benthic vegetation. Finally, in the circalittoral zone, the calcareous red algae of the Corallinales taxon are forming well-structured “maerl-type” biological communities, extended down to 120 m depth under favorable hydrodynamic conditions inhibiting siltation. Both, seagrass meadows and “maerl-type” habitats, are considered as biodiversity hot spots.