gorgonian, black coral and sponge aggregations (see Chap. 10). This diverse group
of habitat-forming taxa provides a three-dimensional structure for refuge and food
for many more benthic species and offers attachment substrates for different sessile
invertebrates (Sebens 1991; Buhl-Mortensen et al. 2010).
Cold-water coral communities (see also Chap. 10) are one of the most emblematic
and diverse habitats in the northeast Atlantic and the Mediterranean, including
the Alboran Sea (Rueda et al. 2019). They are mainly structured by the scleractinian
corals Madrepora oculata and Desmophyllum pertusum (formerly known as
Lophelia pertusa), which are suspension-feeders and require hard substrates to settle
and develop. Their occurrence on areas exposed to constant current regimes
responds to a delicate interplay between the delivery of nutrient particles and
avoidance of excess sedimentary input, which could hinder their development.
However, cold-water corals are also sensitive to the physical characteristics of the
water masses, such as temperature, salinity, pH and oxygen concentration (Gori et al.
2013).
Other scleractinians such as Dendrophyllia cornigera typically occur on the outer
part of the continental shelf and were recorded on rocky bottoms between 40 and
160 m depth around the Alboran Island (Gofas et al. 2014a) and are still found on
coral mounds and the slope (Corbera et al. 2019). The scleractinian Anomocora
fecunda also settles on bathyal hard substrates, as well as other species such as
Caryophyllia calveri, C. smithii and Desmophyllum dianthus which because of their
small size and low density are not considered as habitat-forming taxa but appear as
part of the corals, gorgonian and sponge communities (de la Torriente et al. 2014).
Although corals are the most conspicuous elements, the deep-water rocky-bottom
harbours more concealed associated species which are poorly documented due to the
difficulty of sampling this kind of bottoms. Among other species, the small bivalve
Limopsis angusta has been reported as abundant on Xauen Bank (Salas 1996).
Gorgonians and antipatharians (“black corals”, e.g. Leiopathes glaberrima,
Antipathes dichotoma, Antipathella subpinnata and Parantipathes larix) often
form dense and extensive assemblages in the deep sea, with a great variety of
morphologies (fan-like structure, whips, branched forms, etc.) (see Chap. 10).
Each species develops in those areas where particular environmental conditions
are met: Viminella flagellum alternates dense meadows with sparse colonies and is
usually associated to other soft corals forming mixed gardens. These species are
gradually replaced by others such as Callogorgia verticillata and Acanthogorgia
hirsuta as depth increase. Dense and conspicuous forests of C. verticillata have been
found between 70 and 240 m depth in rocky outcrops around the Alboran Island,
being rather unusual the occurrence of this bathyal species at such shallower bottoms
(Gofas et al. 2014a), and also on dead cold-water coral frameworks, at a depth of
400 m (Corbera et al. 2019). Other smaller species such as Bebryce mollis,
Dendrobrachia bonsai, Muriceides lepida, Paramuricea macrospina, Placogorgia
coronata, P. massiliensis, Swiftia dubia and Villogorgia bebrycoides are also typical
of these communities (de la Torriente et al. 2014, 2018).
The bathyal bottoms of the Alboran Sea shelters a remarkable diversity of
sponges and is the only part of the Mediterranean where aggregations of large
9 Benthic Fauna of Littoral and Deep-Sea Habitats of the Alboran Sea: A. . .
337
of habitat-forming taxa provides a three-dimensional structure for refuge and food
for many more benthic species and offers attachment substrates for different sessile
invertebrates (Sebens 1991; Buhl-Mortensen et al. 2010).
Cold-water coral communities (see also Chap. 10) are one of the most emblematic
and diverse habitats in the northeast Atlantic and the Mediterranean, including
the Alboran Sea (Rueda et al. 2019). They are mainly structured by the scleractinian
corals Madrepora oculata and Desmophyllum pertusum (formerly known as
Lophelia pertusa), which are suspension-feeders and require hard substrates to settle
and develop. Their occurrence on areas exposed to constant current regimes
responds to a delicate interplay between the delivery of nutrient particles and
avoidance of excess sedimentary input, which could hinder their development.
However, cold-water corals are also sensitive to the physical characteristics of the
water masses, such as temperature, salinity, pH and oxygen concentration (Gori et al.
2013).
Other scleractinians such as Dendrophyllia cornigera typically occur on the outer
part of the continental shelf and were recorded on rocky bottoms between 40 and
160 m depth around the Alboran Island (Gofas et al. 2014a) and are still found on
coral mounds and the slope (Corbera et al. 2019). The scleractinian Anomocora
fecunda also settles on bathyal hard substrates, as well as other species such as
Caryophyllia calveri, C. smithii and Desmophyllum dianthus which because of their
small size and low density are not considered as habitat-forming taxa but appear as
part of the corals, gorgonian and sponge communities (de la Torriente et al. 2014).
Although corals are the most conspicuous elements, the deep-water rocky-bottom
harbours more concealed associated species which are poorly documented due to the
difficulty of sampling this kind of bottoms. Among other species, the small bivalve
Limopsis angusta has been reported as abundant on Xauen Bank (Salas 1996).
Gorgonians and antipatharians (“black corals”, e.g. Leiopathes glaberrima,
Antipathes dichotoma, Antipathella subpinnata and Parantipathes larix) often
form dense and extensive assemblages in the deep sea, with a great variety of
morphologies (fan-like structure, whips, branched forms, etc.) (see Chap. 10).
Each species develops in those areas where particular environmental conditions
are met: Viminella flagellum alternates dense meadows with sparse colonies and is
usually associated to other soft corals forming mixed gardens. These species are
gradually replaced by others such as Callogorgia verticillata and Acanthogorgia
hirsuta as depth increase. Dense and conspicuous forests of C. verticillata have been
found between 70 and 240 m depth in rocky outcrops around the Alboran Island,
being rather unusual the occurrence of this bathyal species at such shallower bottoms
(Gofas et al. 2014a), and also on dead cold-water coral frameworks, at a depth of
400 m (Corbera et al. 2019). Other smaller species such as Bebryce mollis,
Dendrobrachia bonsai, Muriceides lepida, Paramuricea macrospina, Placogorgia
coronata, P. massiliensis, Swiftia dubia and Villogorgia bebrycoides are also typical
of these communities (de la Torriente et al. 2014, 2018).
The bathyal bottoms of the Alboran Sea shelters a remarkable diversity of
sponges and is the only part of the Mediterranean where aggregations of large
9 Benthic Fauna of Littoral and Deep-Sea Habitats of the Alboran Sea: A. . .
337