(2013), for example provided an environmental model of the invasion of the
Lessepsian fish Fistularia commersonii and found the Alboran Sea to be one of
the least favourable areas for this invasion.
Few species of fish have been reported as alien in the Alboran Sea, and none of
them seems to be related to anthropogenic causes. This contrasts with, for example
the Catalan coasts, where two highly invasive species (Zebrasoma flavescens and
Balistoides conspicillum) have been reported (Weitzmann et al. 2015), resulting
from an aquarium release. However, several species are considered to be casual o
alien in the Alboran Sea, among them Fistularia petimba, Galeocerdo cuvier,
Gephyroberyx darwini, and Microchirus boscanion (Massutí et al. 2002; Zenetos
et al. 2005).
Among the most impacting alien species are the marine algae. In the last 20 years,
both coasts of the Alboran Sea have been suffering the successive invasion of three
Pacific seaweeds (in order of report Asparagopsis taxiformis, Caulerpa cylindracea,
and Rugulopteryx okamurae), which are deeply altering lower subtidal communities
(Altamirano et al. 2008, 2014, 2017). Maritime transport is suspected to be the main
vector for introducing these species, both from the Strait of Gibraltar and from the
oriental region of the Mediterranean Sea (Boudouresque et al. 2017). The relationship between these invasions and climate change is not clear yet, although some
evidence exists that changes in SST may produce changes in distributional patterns
of these species (Zanolla et al. 2018). The green alga C. cylindracea forms continuous meadows in the Cabo de Gata National Park, and until the recent proliferation
of R. okamurae, also close to the Strait of Gibraltar (Altamirano et al. 2014;
Altamirano et al. 2017). Both species compete with photophilic lower subtidal
communities, such as forests of Gongolaria spp. and Ericaria spp., in both sides
of the Strait of Gibraltar, homogenizing the community to only one species and, in
the case of R. okamurae, producing massive drifted material that hinders the
recreational use of the beaches (Altamirano et al. 2017).
Continuous incoming of propagules of allochthonous species of macroalgae,
transported by merchant ships arriving to the Alboran Sea from the coasts of Pacific
East Asia, together with very weakened native communities due to previous invasions, may presage an increase in the frequency of invasion events in the Alboran
Sea, which may become a driver of transformation of the marine biota in this unique
corner of the Mediterranean. There are impacts from alien species also in the
plankton community. The dinoflagellate Gymnodinium catenatum, originally
described from the Gulf of California (Mexico) and responsible for Paralytic Shellfish Poisoning has become an established species in the Alboran Sea where it causes
frequent toxic events (Calbet et al. 2002).
Researchers from the Spanish Institute of Oceanography (Massuti et al. 2010)
have reported the recent arrival of non-native fish species in the Mediterranean Sea,
in a phenomenon known as “tropicalization”, which may be changing the identity of
the Mediterranean. Their data suggest that in the western Mediterranean, where an
increase in water temperature has been observed during the second half of the
twentieth century, global warming has affected the composition of fish populations.
However, these changes do not occur only due to changes in climate. The variations
450
R. Real et al.
Lessepsian fish Fistularia commersonii and found the Alboran Sea to be one of
the least favourable areas for this invasion.
Few species of fish have been reported as alien in the Alboran Sea, and none of
them seems to be related to anthropogenic causes. This contrasts with, for example
the Catalan coasts, where two highly invasive species (Zebrasoma flavescens and
Balistoides conspicillum) have been reported (Weitzmann et al. 2015), resulting
from an aquarium release. However, several species are considered to be casual o
alien in the Alboran Sea, among them Fistularia petimba, Galeocerdo cuvier,
Gephyroberyx darwini, and Microchirus boscanion (Massutí et al. 2002; Zenetos
et al. 2005).
Among the most impacting alien species are the marine algae. In the last 20 years,
both coasts of the Alboran Sea have been suffering the successive invasion of three
Pacific seaweeds (in order of report Asparagopsis taxiformis, Caulerpa cylindracea,
and Rugulopteryx okamurae), which are deeply altering lower subtidal communities
(Altamirano et al. 2008, 2014, 2017). Maritime transport is suspected to be the main
vector for introducing these species, both from the Strait of Gibraltar and from the
oriental region of the Mediterranean Sea (Boudouresque et al. 2017). The relationship between these invasions and climate change is not clear yet, although some
evidence exists that changes in SST may produce changes in distributional patterns
of these species (Zanolla et al. 2018). The green alga C. cylindracea forms continuous meadows in the Cabo de Gata National Park, and until the recent proliferation
of R. okamurae, also close to the Strait of Gibraltar (Altamirano et al. 2014;
Altamirano et al. 2017). Both species compete with photophilic lower subtidal
communities, such as forests of Gongolaria spp. and Ericaria spp., in both sides
of the Strait of Gibraltar, homogenizing the community to only one species and, in
the case of R. okamurae, producing massive drifted material that hinders the
recreational use of the beaches (Altamirano et al. 2017).
Continuous incoming of propagules of allochthonous species of macroalgae,
transported by merchant ships arriving to the Alboran Sea from the coasts of Pacific
East Asia, together with very weakened native communities due to previous invasions, may presage an increase in the frequency of invasion events in the Alboran
Sea, which may become a driver of transformation of the marine biota in this unique
corner of the Mediterranean. There are impacts from alien species also in the
plankton community. The dinoflagellate Gymnodinium catenatum, originally
described from the Gulf of California (Mexico) and responsible for Paralytic Shellfish Poisoning has become an established species in the Alboran Sea where it causes
frequent toxic events (Calbet et al. 2002).
Researchers from the Spanish Institute of Oceanography (Massuti et al. 2010)
have reported the recent arrival of non-native fish species in the Mediterranean Sea,
in a phenomenon known as “tropicalization”, which may be changing the identity of
the Mediterranean. Their data suggest that in the western Mediterranean, where an
increase in water temperature has been observed during the second half of the
twentieth century, global warming has affected the composition of fish populations.
However, these changes do not occur only due to changes in climate. The variations
450
R. Real et al.