Page 17 - climate-change2013
P. 17

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
   12   13   14   15   16   17   18   19   20   21   22