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Aguilar et al. (2006) recognise a number of European habitats relevant to marine biodiversity,
which they subdivide into physical habitats and biogenic habitats. Physical habitats include: a)
raised features (seamounts, mounds, hills, canyons, trenches, etc.); b) constructive gases
(submarine volcanoes, hydrothermal vents, cold water seeps, etc.); c) caves, caverns and
overhangs; d) pelagic environments (convergence zones, divergence zones, marine currents, etc.);
and e) marine deserts (sandy seabeds, muddy seabeds, stone and gravel seabeds, mixed
sediments seabeds, etc.).
Biogenic habitats include: a) coral reefs (Coralliophila reefs, oculinid reefs, deep-sea soft coral
reefs, etc.); b) mollusc reefs (mytilid reefs, oyster reefs, vermetid reefs, Limidae reefs); c)
crustacean reefs (lepadomorph reefs, balanomorph reefs, mixed crustacean reefs, etc.); d)
polychaete worm reefs (sabellid reefs, mixed polychaete worm reefs, etc.); e) sponge fields and
aggregations (calcareous sponge fields, Hexatinellida sponge fields, Desmospongia sponge fields,
mixed sponge fields, etc.); f) gorgonian gardens (circalittoral gorgonian gardens, deep-sea
gorgonian gardens, etc.); g) seagrass meadows (meadows of Posidonia, Cymodocea, Zostera,
Halophila, etc.); h) green algae meadows (meadows of Caulerpa, Halimeda, etc.); i) brown algae
forests (fucoid and laminarial forests); j) red algal concretions (coralline algae, Maerl beds,
Mesophyllum reefs, laminar forests, trottoirs, Corallinacea seabeds, Peyssonnellinacea seabeds,
etc.); and k) other types of habitats (understories of brown algae, mixed meadows of photophilic
algae and/or carpets of mixed algae, beds of filamentous algae, rockpools, habitats formed by
colonial species of hydrozoans, bryozoans and tunicates, colonial anthozoans or concentrations of
cnidarians, etc.).
Many of these habitats are present in (or confined to) the Mediterranean High Seas, and as host to
significant concentrations of unique and vulnerable marine biodiversity urgently deserve
inventorying, mapping and consideration for protection (Aguilar et al. 2006).
Tudela et al. (2004) identified a number of deep-sea habitat features in the Mediterranean (Fig. 2-
7), including submarine canyons, cold seeps associated to mud volcanoes (harbouring
chemosynthetic communities), cold water coral “reefs”, seamounts and brine pools.

Fig. 2-7. Presently known distribution of deep-sea unique biocenoses in the Mediterranean and
adjacent Atlantic waters (Tudela et al. 2004).