and axinellids typically build in the Mediterranean the so-called “sponge gardens” or
“sponge grounds” in depth ranges which are similar to those reported on NorthAtlantic margins (Maldonado et al. 2016).
Sponges are one of the best studied and more diverse groups in the Alboran Sea
and offer many novelties, as previously noted in Sect. 10.2.1. Specifically, about
200 species have been recorded around the Alboran Island (Sitjà and Maldonado
2014). Here we will focus only on highlighting the most dominant species that make
up sponge gardens.
Among demosponges, the astrophorids Poecillastra compressa and Pachastrella
monilifera appear to have the most extensive geographical distribution within the
Mediterranean and give rise to dense aggregations (reaching densities of up to
10 individuals m
À2 ), sometimes as dominant species and others mixed with corals
and gorgonians (Aguilar et al. 2017). Both species show an Atlantic-Mediterranean
overlapped distribution and share a great morphological and dimensional plasticity,
which allow them to grow into a variety of different environments, on several types
of substrate and within a wide bathymetric range (Bo et al. 2012). They can be
massive, plate-like or cup-like in shape, being P. monilifera generally white, while
P. compressa exhibits orange colour when observed alive. Both species are common
in the deep circalittoral hard bottoms of the Alboran Ridge (Sitjà and Maldonado
2014).
The demosponges of the genus Phakellia, with mostly Atlantic distribution, are
also common in the Western Mediterranean (de la Torriente et al. 2014; Aguilar et al.
2017), becoming abundant in the deep circalittoral and upper bathyal zones, especially on slopy rocky plains and seamounts. Both chalice-shaped or fan-shaped
sponges Phakellia ventilabrum and P. robusta are widespread in the Strait of
Gibraltar and Alboran Sea (Maldonado 1992; Boury-Esnault et al. 1994; Carballo
and García-Gómez 1994; Lo Iacono et al. 2012; Gofas et al. 2014; de la Torriente
et al. 2018). In the Alboran Ridge, Phakellia species have been observed in mixed
assemblages dominated by cnidarians and sponges on the deep circalittoral hard
bottoms (Gofas et al. 2014) and rhodolith beds (Sitjà and Maldonado 2014).
On soft bottoms, the presence of sponge aggregations is limited to a few species,
such as the northwestern Atlantic Thenea muricata, which is also common in muddy
bottoms of the bathyal zone throughout the Mediterranean, including the Alboran
Sea (Boury-Esnault et al. 1994). The T. muricata assemblage is usually monospecific, reaching a high biomass. It is affected by bottom trawling (Pansini and Musso
1991), since it is a common by-catch species.
The northeastern Atlantic large (up to 1 m tall) and vase-shaped hexactinellid
sponge Asconema setubalense is the most important species forming aggregations in
the Western Mediterranean (Boury-Esnault et al. 2015), mainly on seamount rocky
bottoms at depths below 200 m, but has not been found beyond the Alboran Sea.
Another widespread Atlantic glass sponge is Pheronema carpenteri, which can also
give rise to important communities but in this case on muddy bottoms. In the
Mediterranean, it has been found from the Alboran to the Tyrrhenian Sea at depths
between 350 m and more than 2000 m (Boury-Esnault et al. 2015).
10 Invertebrates: The Realm of Diversity
375
“sponge grounds” in depth ranges which are similar to those reported on NorthAtlantic margins (Maldonado et al. 2016).
Sponges are one of the best studied and more diverse groups in the Alboran Sea
and offer many novelties, as previously noted in Sect. 10.2.1. Specifically, about
200 species have been recorded around the Alboran Island (Sitjà and Maldonado
2014). Here we will focus only on highlighting the most dominant species that make
up sponge gardens.
Among demosponges, the astrophorids Poecillastra compressa and Pachastrella
monilifera appear to have the most extensive geographical distribution within the
Mediterranean and give rise to dense aggregations (reaching densities of up to
10 individuals m
À2 ), sometimes as dominant species and others mixed with corals
and gorgonians (Aguilar et al. 2017). Both species show an Atlantic-Mediterranean
overlapped distribution and share a great morphological and dimensional plasticity,
which allow them to grow into a variety of different environments, on several types
of substrate and within a wide bathymetric range (Bo et al. 2012). They can be
massive, plate-like or cup-like in shape, being P. monilifera generally white, while
P. compressa exhibits orange colour when observed alive. Both species are common
in the deep circalittoral hard bottoms of the Alboran Ridge (Sitjà and Maldonado
2014).
The demosponges of the genus Phakellia, with mostly Atlantic distribution, are
also common in the Western Mediterranean (de la Torriente et al. 2014; Aguilar et al.
2017), becoming abundant in the deep circalittoral and upper bathyal zones, especially on slopy rocky plains and seamounts. Both chalice-shaped or fan-shaped
sponges Phakellia ventilabrum and P. robusta are widespread in the Strait of
Gibraltar and Alboran Sea (Maldonado 1992; Boury-Esnault et al. 1994; Carballo
and García-Gómez 1994; Lo Iacono et al. 2012; Gofas et al. 2014; de la Torriente
et al. 2018). In the Alboran Ridge, Phakellia species have been observed in mixed
assemblages dominated by cnidarians and sponges on the deep circalittoral hard
bottoms (Gofas et al. 2014) and rhodolith beds (Sitjà and Maldonado 2014).
On soft bottoms, the presence of sponge aggregations is limited to a few species,
such as the northwestern Atlantic Thenea muricata, which is also common in muddy
bottoms of the bathyal zone throughout the Mediterranean, including the Alboran
Sea (Boury-Esnault et al. 1994). The T. muricata assemblage is usually monospecific, reaching a high biomass. It is affected by bottom trawling (Pansini and Musso
1991), since it is a common by-catch species.
The northeastern Atlantic large (up to 1 m tall) and vase-shaped hexactinellid
sponge Asconema setubalense is the most important species forming aggregations in
the Western Mediterranean (Boury-Esnault et al. 2015), mainly on seamount rocky
bottoms at depths below 200 m, but has not been found beyond the Alboran Sea.
Another widespread Atlantic glass sponge is Pheronema carpenteri, which can also
give rise to important communities but in this case on muddy bottoms. In the
Mediterranean, it has been found from the Alboran to the Tyrrhenian Sea at depths
between 350 m and more than 2000 m (Boury-Esnault et al. 2015).
10 Invertebrates: The Realm of Diversity
375