Page 17 - climate-change2013

Among the most common native species spreading
northwards are fishes such as the ornate wrasse Thalassoma
pavo, the dusky grouper Epinephelus marginatus,
as well as the macroalgae Dasycladus vermicularis.

Epinephelus marginatus. Photo: A. Can - www.alpcan.com Dasycladus vermicularis. Photo: I. Rubio - marmenormarmayor.es

species has been reported throughout this region, as to escape competition within the same thermal environ-
in the case of the round sardinella Sardinella aurita and ment (Milazzo et al., 2013). Therefore, besides changing
one of its predators, the bluefish Pomatomus saltatrix, their geographical ranges, many species could also be
a migratory coastal pelagic species whose northern changing their habitat preferences within their current
boundary was believed to be the southern Catalan areas of distribution.
coast in the western Mediterranean. Both species have
been reported to be increasing in abundance in recent For the slender goby (Gobius geniporus), for exam-
years and expanding northwards into the north-western ple, a species currently found throughout the western,
Mediterranean (Sabates et al., 2006). These changes northern and north-eastern Mediterranean, a climate-
are believed to be associated with higher spring tem- induced range reduction of 80% by the middle of the
peratures, which are crucial for the migration and repro- century has being predicted, restricting its populations
duction of these species. Annual cyclical fluctuations to the Gulf of Lion, southern Sardinia, the northern Adri-
related to natural temperature variations could nonethe- atic and the northern Aegean (Ben Rais Lasram et al.,
less have major consequences for the physiology, fit- 2010).
ness and abundance of these species.
Another example is the European sprat Sprattus sprat-
One of the reasons for the successful range expansion tus, a small schooling pelagic species of high economic
of many of these temperature-sensitive species is their importance that only seems to reproduce in the Gulf of
ability to reproduce in the new areas and establish new Lion and the northern Adriatic Sea (Peck and Mölmann,
populations. A well- documented example of this is the 2008). The northernmost Mediterranean population oc-
recent appearance of juveniles of the dusky grouper curs at its physiological temperature limit and this, in
Epinephelus marginatus in Port Cros National Park combination with intensive fishing, makes this popula-
(France) and other areas along the French continental tion highly vulnerable to climate change.
coast. The increase in the dusky grouper population at
rise in water temperature resulting from climate change Spread of alien species
these sites over the last 10 years is due partly to the
and partly to the success of protection measures that into the Mediterranean
provide the right conditions for reproduction and re-
cruitment in the northern Mediterranean (Harmerlin et
al., 2007). The Mediterranean Sea is subject to a continuous
influx of alien or exotic species arriving through the
Conversely, there is also evidence for a decrease in the Suez Canal or the Strait of Gibraltar, often transported
abundance of some cold-water species from the most by international shipping among other vectors. The
northerly areas of the Mediterranean (the north-western majority of these alien species are thermophilic (warmth-
Mediterranean and northern Adriatic). Suitable habitats requiring species) and the warming sea temperature is
for these cold-water species may also shift because
they cannot compete for limited resources with the
southern species that are moving northwards, and this
may lead to a significant reduction in their populations Alien species —sometimes termed exotic,
and threaten their survival. For example, a recent study introduced or non-native species— are plants
revealed that the changes in the relative abundances and animals that have been intentionally or
of a warm-water species, the ornate wrasse Thalas- unintentionally introduced, have established
soma pavo, and a cold-water species, the rainbow populations and have spread into the wild
wrasse Coris julis, sharing the same habitat can drive in the new host region (IUCN, 2002).
the cold-water species out to less ideal habitats in order

MEDITERRANEAN MARINE PROTECTED AREAS AND CLIMATE CHANGE: A GUIDE TO REGIONAL MONITORING AND ADAPTATION OPPORTUNITIES 15