Status of alien species in the Mediterranean and Black Sea

39
Figure 20 – Main routes of shipping in the Mediterranean Sea
(www.unep.org/geo/geo3/english/fig195.htm)
Verlaque et al. (2007) reported a total of 110 alien marine macrophyte species in the International
Commission for the Scientific Exploration of the Mediterranean Sea (CIESM) Atlas for alien species.
They pointed out several vectors of the alien species such as hulls of ships, fouling, deballasting of
water and solid matter transported by ships, opening of the Suez Canal, intentional and unintentional
introduction.
Ballast water plays a minor role as a vector for introduction of macrophytes to the Mediterranean
(Boudouresque and Verlaque, 2002). Fouling seems to be more important as a vector for their
introduction than ballast water. Oyster transfer which is probably responsible for the introduction of
44 macrophyte species is most important in Thau Lagoon in France (Ribera, 2002; Verlaque, 2001).
Maritime transport is an essential factor for the worldwide dispersal of alien species. In the
Mediterranean, 13 percent of alien plant species were carried on ship’s hulls and 3 percent from
deballasting process (Siguan, 2002). Wyatt and Carlton (2002) reported 7 phytoplankton species
introduced to the European and Mediterranean coastal waters with ballast water, oysters or multiple as
possible vectors. Por (1978), Kovalev (2006) reported several alien zooplankton species which entered
via the Suez Canal and Gibraltar to the Mediterranean Sea. Çiçek and Bilecenoğlu (2009) recently
reported an Indo-Pacific alien fish species likely via ballast water: Champsodon nudivittis. Toxic algae
can be introduced or has been transferred to new environement with ship’s ballast water.
3.2.2 Straits
International straits used for navigation in the Mediterranean and Black Sea are biological corridors at
the same time from the biogeographical point of view (See Figure 21). For example, one of the
intentionally introduced fish species, Liza haematocheila, was first introduced to the Azov Sea and
after the successful colonization it entered to the Black Sea via the Kerch Strait. Later it entered the
Turkish Straits (Istanbul and Çanakkale) and is currently found in the Aegean Sea (Kaya et al., 1998)
and the Mediterranean Sea. There are some other examples such as Rapana venosa and Mnemiopsis
leidyi. They were first recorded in the Black Sea and after its successful migration through the Turkish
Straits, they penetrated to the Aegean and Mediterranean Seas.
On the other end of the Mediterranean, the Gibraltar Strait is also a long biological corridor for alien
species from the Atlantic Ocean. The Atlantic-Mediterranean faunistic connection had an impact on