focal points for recreational diving. Together with other main sources of human
perturbation (e.g. coastal pollution, climate change), physical impacts due to scuba
diving activities and fishing gear are noticeable due to the high fragility and low
growth rate of calcareous organisms (Ballesteros 2006).
9.4.5 Circalittoral Hard Bottoms with Coralligenous
Communities
Coralligenous communities represent complex bioconstructions developed over a
basal layer of calcareous algal species and secondarily by different sessile and filter
feeding macroinvertebrates with calcareous skeletons (e.g. anthozoans, sponges,
serpulid annelids, bryozoans), which thrive under dim-light conditions on rocky
crests, walls, overhangs and crevices, supporting high levels of biodiversity and a
complex trophic net (Ballesteros 2006). This is an emblematic habitat in the Mediterranean Sea, locally starting in the infralittoral zone below 20 m (precoralligenous,
see above) and widely developed in the circalittoral zone, where conditions of
temperature, currents and salinity are relatively constant (Laborel 1987; Ballesteros
2006). Overall, the composition of the coralligenous community is highly determined by depth and the relief of rocky outcrops, becoming considerably different
from one place to another separated horizontally or vertically by few meters, which
promotes high species richness.
Coralligenous communities at circalittoral depths have been recently studied in
detail in areas included within the Natura 2000 network (EU Habitat Directive) such
as the Alboran Island (Gofas et al. 2014a; Sitjà and Maldonado 2014) and the Seco
de los Olivos (de la Torriente et al. 2014), in the framework of the EU LIFE+
INDEMARES project. Coralligenous communities develop on rocky substrates that
occupy large areas of the Alboran platform (30–100 m depth), mainly in the southern
flank and in the southwestern outcrop and on the shallowest areas of the Seco de los
Olivos (ca. 100 m depth), where light conditions still allow the growth of calcareous
red algal species. The calcareous basal layer is mainly composed of Lithophyllum
stictiforme and Neogoniolithon mamillosum in Alboran, plus Mesophyllum
alternans in the Seco, and represents a hard substratum that is colonized by sessile
large-size animals with bioconstruction potential.
Overall, gorgonians are the most characteristic taxa in this community, with
Eunicella verrucosa, Paramuricea clavata and Leptogorgia sarmentosa
(Fig. 9.12) dominating between 30 and 90 m depth. Secondary typifying species at
this depth range include other anthozoans such as the zoantharian Savalia savaglia,
the black coral Antipathella subpinnata, the soft octocoral Alcyonium acaule and the
coral Dendrophyllia ramea (de la Torriente et al. 2014; Gofas et al. 2014a).
The sponge fauna also represents an important component of the coralligenous
community, with a great amount of encrusting, branching and massive sponges
sharing habitat with the octocorals. This faunal component has been deeply studied
9 Benthic Fauna of Littoral and Deep-Sea Habitats of the Alboran Sea: A. . .
313
perturbation (e.g. coastal pollution, climate change), physical impacts due to scuba
diving activities and fishing gear are noticeable due to the high fragility and low
growth rate of calcareous organisms (Ballesteros 2006).
9.4.5 Circalittoral Hard Bottoms with Coralligenous
Communities
Coralligenous communities represent complex bioconstructions developed over a
basal layer of calcareous algal species and secondarily by different sessile and filter
feeding macroinvertebrates with calcareous skeletons (e.g. anthozoans, sponges,
serpulid annelids, bryozoans), which thrive under dim-light conditions on rocky
crests, walls, overhangs and crevices, supporting high levels of biodiversity and a
complex trophic net (Ballesteros 2006). This is an emblematic habitat in the Mediterranean Sea, locally starting in the infralittoral zone below 20 m (precoralligenous,
see above) and widely developed in the circalittoral zone, where conditions of
temperature, currents and salinity are relatively constant (Laborel 1987; Ballesteros
2006). Overall, the composition of the coralligenous community is highly determined by depth and the relief of rocky outcrops, becoming considerably different
from one place to another separated horizontally or vertically by few meters, which
promotes high species richness.
Coralligenous communities at circalittoral depths have been recently studied in
detail in areas included within the Natura 2000 network (EU Habitat Directive) such
as the Alboran Island (Gofas et al. 2014a; Sitjà and Maldonado 2014) and the Seco
de los Olivos (de la Torriente et al. 2014), in the framework of the EU LIFE+
INDEMARES project. Coralligenous communities develop on rocky substrates that
occupy large areas of the Alboran platform (30–100 m depth), mainly in the southern
flank and in the southwestern outcrop and on the shallowest areas of the Seco de los
Olivos (ca. 100 m depth), where light conditions still allow the growth of calcareous
red algal species. The calcareous basal layer is mainly composed of Lithophyllum
stictiforme and Neogoniolithon mamillosum in Alboran, plus Mesophyllum
alternans in the Seco, and represents a hard substratum that is colonized by sessile
large-size animals with bioconstruction potential.
Overall, gorgonians are the most characteristic taxa in this community, with
Eunicella verrucosa, Paramuricea clavata and Leptogorgia sarmentosa
(Fig. 9.12) dominating between 30 and 90 m depth. Secondary typifying species at
this depth range include other anthozoans such as the zoantharian Savalia savaglia,
the black coral Antipathella subpinnata, the soft octocoral Alcyonium acaule and the
coral Dendrophyllia ramea (de la Torriente et al. 2014; Gofas et al. 2014a).
The sponge fauna also represents an important component of the coralligenous
community, with a great amount of encrusting, branching and massive sponges
sharing habitat with the octocorals. This faunal component has been deeply studied
9 Benthic Fauna of Littoral and Deep-Sea Habitats of the Alboran Sea: A. . .
313