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envelopes, against local environmental conditions to determine the relative suitability of specific
geographic areas for a given species. Knowledge of species’ distributions within FAO areas or
bounding boxes is also used to exclude potentially suitable habitat in which the species is not
known to occur. We anticipate that as data will continue flowing into the AquaMaps meta-
database; this will soon become a very useful tool to support decisions concerning the
establishment of High Seas MPAs networks.

Fig. 2-8. Species-richness distribution of 79 deep sea marine species in the Mediterranean and
adjacent seas proposed by AquaMaps (Kaschner et al. 2008).

The deep-water fauna of the Mediterranean is characterized by an absence of distinctive
characteristics and by a relative impoverishment. Both are a result of events after the Messinian
salinity crisis (Late Miocene). The three main classes of phenomena involved in producing or
recording these effects are:

• historical: sequential faunal changes during the Pliocene and thereafter in particular those
during the Quaternary glaciations and still in progress;

• bathymetric: changes in the vertical aspects of the bathyal and abyssal zones that took
place under peculiar conditions, i.e. homothermy, a relative oligotrophy, the barrier of the
Gibraltar sill, and water mass movement. The deeper the habitat of a species in the
Mediterranean, the more extensive is its distribution elsewhere;

• geographical: there are strong affinities and relationships between Mediterranean and
Atlantic faunas. Endemic species remain a biogeographical problem. Species always
become smaller in size eastward where they occupy a progressively deeper habitat (Emig
and Geistdoerfer, 2004).

The Mediterranean Sea includes 6% of the world's species for less than 1% of the world's ocean
surface area and 0.3% of its volume. The number of endemic species is significantly higher than
that for the Atlantic Ocean (Bianchi and Morri 2000). The percentage of endemism is very high for
the sessile or sedentary groups such as ascidians with 50.4%, sponges with 42.4%, hydroids with
27.1%, echinoderms with 24.3%, but it is also considerable for the other groups such as decapod