Page 18 - climate-change2013

favouring their rapid spread northwards and westwards
in the Mediterranean. The fastest reported of these
colonizers is the bluespotted cornetfish Fistularia
commersonii, which has been able to develop large
populations in the warm eastern areas and colonize
the entire Mediterranean from there in less than 10
years (Azzurro et al., 2012). Other species such as two
rabbitfishes Siganus luridus and S. rivulatus and the
ascidians Phallusia nigra and Herdmania momus have
become very common in most parts of the eastern
Mediterranean and strongly interact with native species.

The case of Kas-Kekova MPA off Turkey’s south-west-
ern Lycian coast is a good example of the impact of
invasive species. Here two invasive rabbitfish species
from the Red Sea (Siganus luridus and S. rivulatus)
are responsible for creating and maintaining underwa-
ter barren grounds composed solely of bare rock and
patches of crustose coralline algae. These warm-water
species are naturally extending their range through the
eastern basin towards the northern parts of the Medi-
terranean.
Photo: P. Bodilis - ECOMERS

The rabbitfish Siganus luridus has become
very common in most parts of the eastern
Mediterranean and strongly compete with
native herbivorous fish species. Their
spread can result in a drastic decrease in
seaweed formations.

Invasive: alien species which become
established in natural or semi-natural
ecosystems or habitats and become an
agent of change, increasing in abundance
and distribution and threatening native
biological diversity (IUCN, revised 2012).

Climate change is thus not only enabling some exist-
ing exotic species to spread into other areas, but it is
likely to create welcoming conditions for new invaders
or serve as a trigger for these exotics to become inva-
sive. The outcome of the readjustment of interactions Photo: J. Garrabou
by the local native populations will vary, depending on
multiple factors. Overall, the result may have a profound
impact on both the biodiversity and the functioning of A healthy specimen and different mortality stages
the Mediterranean sublittoral ecosystems where most in Mediterranean keratose sponges
MPAs are established.

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