2014); and many cnidarians. Among the latter, the gorgonian Eunicella filiformis lies
loose on the bottom; the hydroids Modeeria rotunda and Aglaophenia tubulifera, the
solitary coral Caryophyllia spp. and the gorgonian Leptogorgia sarmentosa settle on
large bioclasts; and some sea pens (Veretillum cynomorium, Pennatula rubra) may
also occur. The annelid Hyalinoecia tubicola crawls over the sediment, Lanice
conchilega builds a semi-buried tube, and serpulids settle on the bioclasts. Among
molluscs, the most frequent species are the gastropods Anatoma aspera, Clelandella
miliaris, Calyptraea chinensis, Fusinus pulchellus, Orania fusulus and Xenophora
crispa as well as the rare and protected cowry Schilderia achatidea and the bivalves
Bathyarca pectunculoides, Parvamussium fenestratum, Neopycnodonte cochlear,
Arca tetragona and Parvicardium minimum. The most common decapods are
Inachus dorsettensis, Munida speciosa, Galathea intermedia, Anapagurus
breviaculeatus, Pagurus prideaux, Eurynome aspera and Ebalia granulosa. The
crinoid Antedon mediterranea, the starfishes Anseropoda placenta and Chaetaster
longipes, the holothurian Parastichopus regalis and different ophiuroids
(Ophiothrix quinquemaculata) are representative of the echinoderms. The bryozoans
Cellaria salicornioides and Reteporella spp. and the ascidian Molgula
appendiculata grow commonly on medium-sized bioclasts. Interestingly, a part of
Alboran platform shelf bioclasts is composed of subfossil shells of Modiolus
modiolus and other boreal species that inhabited these bottoms and then close to
the coast due to lower sea level, during the last Ice Age.
Despite their unquestionable species richness, bioclastic gravels do not benefit
from any kind of formal protection other than being encompassed in marine
protected areas designated for other components. Perspectives for specific protection
are scant because these bottoms are a major target for trawling and because they can
be very extensive. A fair representation of coastal bioclastic gravels is found in
Parque Natural del Estrecho, in the Calahonda Special Area of Conservation and in
the “Site d’Intérêt Biologique et Ecologique” of Jbel Moussa among others. The
deeper “shelf edge” gravels are included in the offshore Special Areas of Conservation planned on the Alboran Platform and Seco de los Olivos (Gofas et al. 2014a; de
la Torriente et al. 2014).
9.6.4 “Maërl”/Rhodolith Beds
“Maërl” or rhodolith beds are defined by the presence of free-living calcareous red
algae over the underlying sediment. The Breton word “maërl” was used since 1867
for Atlantic bottoms of this kind off the NW coast of France, mainly formed by the
branched calcareous algae Phymatolithon calcareum and Lithothamnion
corallioides (Cabioch 1969). The term “rhodolith” (Ginsburg and Bosellini 1973),
meaning red stone, was subsequently coined to designate unattached nodules formed
by coralline algae, spanning a large array of forms (branched or not) and sizes (from
a few millimetres to over 10 cm), and this term became used worldwide (Bosence
1983a, b; Foster 2001). Both “maërl” and “rhodolith” are often used indifferently
330
J. L. Rueda et al.
loose on the bottom; the hydroids Modeeria rotunda and Aglaophenia tubulifera, the
solitary coral Caryophyllia spp. and the gorgonian Leptogorgia sarmentosa settle on
large bioclasts; and some sea pens (Veretillum cynomorium, Pennatula rubra) may
also occur. The annelid Hyalinoecia tubicola crawls over the sediment, Lanice
conchilega builds a semi-buried tube, and serpulids settle on the bioclasts. Among
molluscs, the most frequent species are the gastropods Anatoma aspera, Clelandella
miliaris, Calyptraea chinensis, Fusinus pulchellus, Orania fusulus and Xenophora
crispa as well as the rare and protected cowry Schilderia achatidea and the bivalves
Bathyarca pectunculoides, Parvamussium fenestratum, Neopycnodonte cochlear,
Arca tetragona and Parvicardium minimum. The most common decapods are
Inachus dorsettensis, Munida speciosa, Galathea intermedia, Anapagurus
breviaculeatus, Pagurus prideaux, Eurynome aspera and Ebalia granulosa. The
crinoid Antedon mediterranea, the starfishes Anseropoda placenta and Chaetaster
longipes, the holothurian Parastichopus regalis and different ophiuroids
(Ophiothrix quinquemaculata) are representative of the echinoderms. The bryozoans
Cellaria salicornioides and Reteporella spp. and the ascidian Molgula
appendiculata grow commonly on medium-sized bioclasts. Interestingly, a part of
Alboran platform shelf bioclasts is composed of subfossil shells of Modiolus
modiolus and other boreal species that inhabited these bottoms and then close to
the coast due to lower sea level, during the last Ice Age.
Despite their unquestionable species richness, bioclastic gravels do not benefit
from any kind of formal protection other than being encompassed in marine
protected areas designated for other components. Perspectives for specific protection
are scant because these bottoms are a major target for trawling and because they can
be very extensive. A fair representation of coastal bioclastic gravels is found in
Parque Natural del Estrecho, in the Calahonda Special Area of Conservation and in
the “Site d’Intérêt Biologique et Ecologique” of Jbel Moussa among others. The
deeper “shelf edge” gravels are included in the offshore Special Areas of Conservation planned on the Alboran Platform and Seco de los Olivos (Gofas et al. 2014a; de
la Torriente et al. 2014).
9.6.4 “Maërl”/Rhodolith Beds
“Maërl” or rhodolith beds are defined by the presence of free-living calcareous red
algae over the underlying sediment. The Breton word “maërl” was used since 1867
for Atlantic bottoms of this kind off the NW coast of France, mainly formed by the
branched calcareous algae Phymatolithon calcareum and Lithothamnion
corallioides (Cabioch 1969). The term “rhodolith” (Ginsburg and Bosellini 1973),
meaning red stone, was subsequently coined to designate unattached nodules formed
by coralline algae, spanning a large array of forms (branched or not) and sizes (from
a few millimetres to over 10 cm), and this term became used worldwide (Bosence
1983a, b; Foster 2001). Both “maërl” and “rhodolith” are often used indifferently
330
J. L. Rueda et al.