of the strait, there are long sandy beaches such as Caños de Meca on the Atlantic side
or La Línea de la Concepción on the Mediterranean one.
Most of the studies on communities from sublittoral soft bottoms have been
carried out in the northern margin of this basin, such as the Gibraltar area (Rueda
et al. 2000; Rueda and Salas 2003), the littoral of Málaga province (García Raso
1982, 1983, 1987; Salas et al. 1984; Salas 1987; Urra et al. 2011, 2013c), the littoral
of Granada province (Rueda et al. 2009a, b; Marina et al. 2015) or the bay of Almería
(Rodríguez and Ibáñez 1976). The African part of the Alboran Sea has been less
sampled and studied. In Morocco there are some data from few areas, such as the
National Park of Al Hoceima (UICN 2012), Cap des Trois Fourches (Bazairi et al.
2013) and Jbel Moussa (Bazairi et al. 2016). The infralittoral soft bottom in these
areas is represented by fine sand in the sheltered bays, from 3 to 20–30 m depth,
some of them bordered by Cymodocea nodosa meadows, while in the capes the
bottom is mainly coarse bioclastic sand. In Algeria the data from the Alboran margin
are from the littoral of Oran (Hussein 2015) and Rachgoun Island (Ramos-Esplá
et al. 2016). In the latter, most of the infralittoral zone is occupied by rock with
photophilous algae, with Posidonia beds in the southern littoral of the island. The
infralittoral soft bottom of the Oran area is mainly represented by coarse bioclastic
sand with meadows of Posidonia oceanica and Cymodocea nodosa (Hussein 2015).
In general, the most extensively represented infralittoral biosedimentary units in
the Alboran Sea are the shallower well-sorted fine sands, coastal bioclastic sand and
gravel and coastal terrigenous muds, the latter in areas with less current and usually
under influence of rivers or aquaculture facilities which supply the mud.
9.6.1 Well-Sorted Fine Sand
This assemblage is located in the shallower part of the infralittoral zone, usually
between 1 and about 20 m, but there are substantial differences between the surf zone
and the deeper parts (Pérès and Picard 1964; Dauvin et al. 2017). The surf zone
(1–3 m) is characterized by high instability due to strong wave action, and the
bottom is medium-grained sand. The faunistic assemblages show low species
richness and high dominances. Below, where the waves no longer have a direct
effect, there are very homogenous sands of terrigenous origin with low mud content,
the so-called well-sorted fine sands. These bottoms are usually devoid of macrophytes (except for seagrasses, see below). Most of their fauna belongs to the infauna,
and their surface is apparently barren (Fig. 9.16). Altogether, this is probably the
most extensive infralittoral habitat.
In the surf zone, the bivalve Donax trunculus (locally known in Spain as coquina)
is the most characteristic mollusc, together with the Mediterranean Donax
semistriatus and the Atlantic Donax vittatus (Salas 1987), the Mediterranean
nassarid Tritia grana, as well as the tropical West African naticid Sinum bifasciatum
(only occasionally, and restricted to the coast of Málaga) (Gofas et al. 2011). Among
the decapod crustaceans, the characteristic species are Philocheras trispinosus,
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J. L. Rueda et al.
or La Línea de la Concepción on the Mediterranean one.
Most of the studies on communities from sublittoral soft bottoms have been
carried out in the northern margin of this basin, such as the Gibraltar area (Rueda
et al. 2000; Rueda and Salas 2003), the littoral of Málaga province (García Raso
1982, 1983, 1987; Salas et al. 1984; Salas 1987; Urra et al. 2011, 2013c), the littoral
of Granada province (Rueda et al. 2009a, b; Marina et al. 2015) or the bay of Almería
(Rodríguez and Ibáñez 1976). The African part of the Alboran Sea has been less
sampled and studied. In Morocco there are some data from few areas, such as the
National Park of Al Hoceima (UICN 2012), Cap des Trois Fourches (Bazairi et al.
2013) and Jbel Moussa (Bazairi et al. 2016). The infralittoral soft bottom in these
areas is represented by fine sand in the sheltered bays, from 3 to 20–30 m depth,
some of them bordered by Cymodocea nodosa meadows, while in the capes the
bottom is mainly coarse bioclastic sand. In Algeria the data from the Alboran margin
are from the littoral of Oran (Hussein 2015) and Rachgoun Island (Ramos-Esplá
et al. 2016). In the latter, most of the infralittoral zone is occupied by rock with
photophilous algae, with Posidonia beds in the southern littoral of the island. The
infralittoral soft bottom of the Oran area is mainly represented by coarse bioclastic
sand with meadows of Posidonia oceanica and Cymodocea nodosa (Hussein 2015).
In general, the most extensively represented infralittoral biosedimentary units in
the Alboran Sea are the shallower well-sorted fine sands, coastal bioclastic sand and
gravel and coastal terrigenous muds, the latter in areas with less current and usually
under influence of rivers or aquaculture facilities which supply the mud.
9.6.1 Well-Sorted Fine Sand
This assemblage is located in the shallower part of the infralittoral zone, usually
between 1 and about 20 m, but there are substantial differences between the surf zone
and the deeper parts (Pérès and Picard 1964; Dauvin et al. 2017). The surf zone
(1–3 m) is characterized by high instability due to strong wave action, and the
bottom is medium-grained sand. The faunistic assemblages show low species
richness and high dominances. Below, where the waves no longer have a direct
effect, there are very homogenous sands of terrigenous origin with low mud content,
the so-called well-sorted fine sands. These bottoms are usually devoid of macrophytes (except for seagrasses, see below). Most of their fauna belongs to the infauna,
and their surface is apparently barren (Fig. 9.16). Altogether, this is probably the
most extensive infralittoral habitat.
In the surf zone, the bivalve Donax trunculus (locally known in Spain as coquina)
is the most characteristic mollusc, together with the Mediterranean Donax
semistriatus and the Atlantic Donax vittatus (Salas 1987), the Mediterranean
nassarid Tritia grana, as well as the tropical West African naticid Sinum bifasciatum
(only occasionally, and restricted to the coast of Málaga) (Gofas et al. 2011). Among
the decapod crustaceans, the characteristic species are Philocheras trispinosus,
320
J. L. Rueda et al.