Sargassum vulgare, or the relict tropical species Dasycladus vermicularis and
Acetabularia acetabulum, both restricted to the most eastern area of the Alboran
Sea (Fig. 8.7b). Asparagopsis armata and A. taxiformis are very characteristic
elements and in many cases are the dominant species of the underwater landscape
of this biocenosis (Fig. 8.7c).
A community widespread at this level, and which characterizes large areas of the
rocky underwater landscape of the Alboran Sea, is the so-called community of
encrusting red seaweed and sea urchins. This community derives from the community of photophilic algae, in which excessive grazing by sea urchins (Paracentrotus
lividus and Arbacia lixula) causes the total disappearance of the erect algal component. Such overgrazing leaves only the calcareous encrusting thalli of species of red
algae, the most usual being Lithophyllum incrustans, recognizable by its characteristic white-pink color (Fig. 8.7d).
In areas with a significant limitation of light, either by depth or by the contours of
the substrate, the community of hemisciophilous algae, so-called precoralligenous
community, is developed. This community is a transition between the infralittoral
and circalittoral zones. In these shaded environments, some species of algae are
adapted to these low-light conditions. Cystoseira usneoides, a larger species, forms
important forests in certain areas of the Alboran Sea (Fig. 8.8a). As was the case in
the previous community, the typical Cystoseira species of this community are also
usually absent, with Asparagopsis spp. being the most important and abundant
elements. At Alboran Island, this community maintains high levels of coverage
and development, even though the population of the sea urchin Sphaerechinus
granularis is also very high, so the absence of these communities in the rest of the
Alboran Sea coast may be more related to pollution or competition with
Asparagopsis spp. than with excessive grazing by sea urchins. Among the species
appearing with C. usneoides are Halopteris filicina, Dictyopteris polypodioides,
Zonaria tournefortii, Sphaerococcus coronopifolius, Plocamiun cartilagineum,
Codium bursa, C. vermilara, C. effusum, Flabellia petiolata, Valonia macrophysa,
Bryopsis plumosa, B. cupressina, Lithophyllum stictaeforme, Peyssonnelia spp.,
Mesophyllum alternans (which forms large calcareous concretions), or Halimeda
tuna (present in the easternmost part of the Alboran Sea). In these populations of
Cystoseira usneoides, frequently species of Laminariales have better development in
zones at greater depths.
At greater depths than in the communities of C. usneoides, forests of the large
kelps Laminaria ochroleuca and Saccorhiza polyschides develop (Fig. 8.8b). The
underwater landscape dominated by these large algae forms a well-structured and
stratified community with a high associated biodiversity that can penetrate into the
circalittoral zone. Under the canopy of these large kelps proliferate the small kelps
Phyllariopsis purpurascens and P. brevipes, together with C. usneoides. Other
species associated with these communities are in general the same ones found in
the previous mentioned C. usneoides formations, together with other species such as
Fauchea repens, Halymenia floresia, Gelidium spp., Kallymenia spp. and Sebdenia
spp. The species of Phyllariopsis can form their own communities at deeper levels
8 Seaweeds and Seagrasses: The Marine Forests from the Alboran Sea
261
Acetabularia acetabulum, both restricted to the most eastern area of the Alboran
Sea (Fig. 8.7b). Asparagopsis armata and A. taxiformis are very characteristic
elements and in many cases are the dominant species of the underwater landscape
of this biocenosis (Fig. 8.7c).
A community widespread at this level, and which characterizes large areas of the
rocky underwater landscape of the Alboran Sea, is the so-called community of
encrusting red seaweed and sea urchins. This community derives from the community of photophilic algae, in which excessive grazing by sea urchins (Paracentrotus
lividus and Arbacia lixula) causes the total disappearance of the erect algal component. Such overgrazing leaves only the calcareous encrusting thalli of species of red
algae, the most usual being Lithophyllum incrustans, recognizable by its characteristic white-pink color (Fig. 8.7d).
In areas with a significant limitation of light, either by depth or by the contours of
the substrate, the community of hemisciophilous algae, so-called precoralligenous
community, is developed. This community is a transition between the infralittoral
and circalittoral zones. In these shaded environments, some species of algae are
adapted to these low-light conditions. Cystoseira usneoides, a larger species, forms
important forests in certain areas of the Alboran Sea (Fig. 8.8a). As was the case in
the previous community, the typical Cystoseira species of this community are also
usually absent, with Asparagopsis spp. being the most important and abundant
elements. At Alboran Island, this community maintains high levels of coverage
and development, even though the population of the sea urchin Sphaerechinus
granularis is also very high, so the absence of these communities in the rest of the
Alboran Sea coast may be more related to pollution or competition with
Asparagopsis spp. than with excessive grazing by sea urchins. Among the species
appearing with C. usneoides are Halopteris filicina, Dictyopteris polypodioides,
Zonaria tournefortii, Sphaerococcus coronopifolius, Plocamiun cartilagineum,
Codium bursa, C. vermilara, C. effusum, Flabellia petiolata, Valonia macrophysa,
Bryopsis plumosa, B. cupressina, Lithophyllum stictaeforme, Peyssonnelia spp.,
Mesophyllum alternans (which forms large calcareous concretions), or Halimeda
tuna (present in the easternmost part of the Alboran Sea). In these populations of
Cystoseira usneoides, frequently species of Laminariales have better development in
zones at greater depths.
At greater depths than in the communities of C. usneoides, forests of the large
kelps Laminaria ochroleuca and Saccorhiza polyschides develop (Fig. 8.8b). The
underwater landscape dominated by these large algae forms a well-structured and
stratified community with a high associated biodiversity that can penetrate into the
circalittoral zone. Under the canopy of these large kelps proliferate the small kelps
Phyllariopsis purpurascens and P. brevipes, together with C. usneoides. Other
species associated with these communities are in general the same ones found in
the previous mentioned C. usneoides formations, together with other species such as
Fauchea repens, Halymenia floresia, Gelidium spp., Kallymenia spp. and Sebdenia
spp. The species of Phyllariopsis can form their own communities at deeper levels
8 Seaweeds and Seagrasses: The Marine Forests from the Alboran Sea
261