Isidella elongata, known as bamboo coral, is the main tree-like species on deep
bathyal compact muds (it characterizes a facies together with the sea pen Funiculina
quadrangularis) between about 500 and 1200 m depth (occasionally shallower) on
relatively flat bottoms with a gentle slope (Cartes et al. 2013; Mastrototaro et al.
2017). The bamboo coral (with colonies up to 70 cm height) is almost exclusively
restricted to the Mediterranean Sea, but it can extend to the adjacent Gulf of Cadiz
and North Morocco. Maynou and Cartes (2012) pointed out that some fish and
decapod crustaceans reach maximum abundance in bottoms where I. elongata
reaches a high density, such as the deep-water shrimps Aristeus antennatus and
Plesionika martia, both of high commercial interest. In fact, this deep-water coral is
increasingly rare in the Mediterranean due to intense fishing pressure from trawlers
targeting the red shrimp (Aristeus antennatus) at continental slope depths, so nowadays the species is considered Critically Endangered (Otero et al. 2017;
Pierdomenico et al. 2018). In the Alboran Sea has been recorded in the Djibouti,
Cabliers and Chella Banks, with a maximum density in the depth range of
400–500 m (de la Torriente et al. 2014).
All gorgonian species mentioned above are considered to be the most frequent in
the Strait of Gibraltar and Alboran Sea, but there are also a number of other
gorgonian species that have been recorded sporadically in this area, such as
Filigorgia guineensis (Ocaña et al. 2000), Paramuricea grayi (Ocaña et al. 2009),
Dendrobrachia bonsai, Placogorgia coronata (de la Torriente et al. 2014),
Placogorgia massiliensis, Spinimuricea atlantica or Nicella granifera (Ocaña
et al. 2017).
Regarding species conservation, three gorgonians (Savalia savaglia, Callogorgia
verticillata and Ellisella paraplexauroides) have been recently included in Annex II
of the Barcelona Convention.
10.3.3 Red Coral
The emblematic Mediterranean red coral Corallium rubrum belongs to the same
group as gorgonians (order Alcyonacea, formerly Gorgonacea), but unlike the
gorgonians (suborder Holaxonia), which have a flexible skeleton of a corneous
nature, in C. rubrum (suborder Scleraxonia), the skeleton is hard calcified. It is a
typical Mediterranean species widely distributed throughout the basin and into the
neighbouring Atlantic Ocean from Portugal to Moroccan coasts (Boavida et al.
2016), and there are some scattered records in Canary Islands and Cape Verde
Islands (Brito and Ocaña 2004).
The red coral is a sciaphilous long-lived species (a colony can live for more than
100 years) with low growth and reproductive rates and a very restricted dispersion
ability (Cau et al. 2013). It inhabits a wide depth range from shallow-water caves in
the infralittoral zone to depths greater than 1000 m in the bathyal zone (Rossi et al.
2008; Costantini et al. 2010; Taviani et al. 2010; Knittweis et al. 2016) although
more commonly at 30–200 m. Although it may form single-species forests on rocky
382
J. Templado et al.
bathyal compact muds (it characterizes a facies together with the sea pen Funiculina
quadrangularis) between about 500 and 1200 m depth (occasionally shallower) on
relatively flat bottoms with a gentle slope (Cartes et al. 2013; Mastrototaro et al.
2017). The bamboo coral (with colonies up to 70 cm height) is almost exclusively
restricted to the Mediterranean Sea, but it can extend to the adjacent Gulf of Cadiz
and North Morocco. Maynou and Cartes (2012) pointed out that some fish and
decapod crustaceans reach maximum abundance in bottoms where I. elongata
reaches a high density, such as the deep-water shrimps Aristeus antennatus and
Plesionika martia, both of high commercial interest. In fact, this deep-water coral is
increasingly rare in the Mediterranean due to intense fishing pressure from trawlers
targeting the red shrimp (Aristeus antennatus) at continental slope depths, so nowadays the species is considered Critically Endangered (Otero et al. 2017;
Pierdomenico et al. 2018). In the Alboran Sea has been recorded in the Djibouti,
Cabliers and Chella Banks, with a maximum density in the depth range of
400–500 m (de la Torriente et al. 2014).
All gorgonian species mentioned above are considered to be the most frequent in
the Strait of Gibraltar and Alboran Sea, but there are also a number of other
gorgonian species that have been recorded sporadically in this area, such as
Filigorgia guineensis (Ocaña et al. 2000), Paramuricea grayi (Ocaña et al. 2009),
Dendrobrachia bonsai, Placogorgia coronata (de la Torriente et al. 2014),
Placogorgia massiliensis, Spinimuricea atlantica or Nicella granifera (Ocaña
et al. 2017).
Regarding species conservation, three gorgonians (Savalia savaglia, Callogorgia
verticillata and Ellisella paraplexauroides) have been recently included in Annex II
of the Barcelona Convention.
10.3.3 Red Coral
The emblematic Mediterranean red coral Corallium rubrum belongs to the same
group as gorgonians (order Alcyonacea, formerly Gorgonacea), but unlike the
gorgonians (suborder Holaxonia), which have a flexible skeleton of a corneous
nature, in C. rubrum (suborder Scleraxonia), the skeleton is hard calcified. It is a
typical Mediterranean species widely distributed throughout the basin and into the
neighbouring Atlantic Ocean from Portugal to Moroccan coasts (Boavida et al.
2016), and there are some scattered records in Canary Islands and Cape Verde
Islands (Brito and Ocaña 2004).
The red coral is a sciaphilous long-lived species (a colony can live for more than
100 years) with low growth and reproductive rates and a very restricted dispersion
ability (Cau et al. 2013). It inhabits a wide depth range from shallow-water caves in
the infralittoral zone to depths greater than 1000 m in the bathyal zone (Rossi et al.
2008; Costantini et al. 2010; Taviani et al. 2010; Knittweis et al. 2016) although
more commonly at 30–200 m. Although it may form single-species forests on rocky
382
J. Templado et al.