a lower extent by P. gracilis (Andersen et al. 2004). Other abundant copepods
recorded by these authors around this front are Subeucalanus monachus, Eucalanus
hyalinus, Clausocalanus furcatus and Centropages typicus.
Cladocerans, which exhibit a seasonal and/or aggregative distribution, are
represented by few species, but they can be very abundant in coastal waters, such
as Penilia avirostris, Pseudevadne tergestina, Evadne spinifera and E. nordmanni
(Rodríguez 1983). On the other hand, ostracods, which are not numerous in the
mesozooplankton communities at temperate latitudes, are more abundant in deep
waters than in the epipelagic zone (Siokou-Frangou et al. 2010).
The macroplankton of the Alboran Sea consists essentially of euphausiids,
chaetognaths and gelatinous zooplankton. According to Madin (1991), the dominant
euphausiid species occurring were Euphausia krohnii, Nematoscelis megalops,
Stylocheiron abbreviatum and S. suhmi, with maximum abundances in summer.
Chaetognaths are active predators and an important component of zooplankton.
They are well represented in the Alboran Sea by more than a dozen species (Camiñas
1985) that become very abundant in areas of higher biomass, such as in the vicinity
of the Almería-Oran Front. According to this author, the most abundant chaetognaths in the area are Parasagitta friderici, Serratosagitta tasmanica, Pterosagitta
draco, Flacisagitta enflata and Decipisagitta decipiens.
Three main phyla, the carnivorous Cnidaria and Ctenophora and the filterfeeding Tunicata, dominate the gelatinous macroplankton (Fig. 10.15). These
holoplanktonic organisms exhibit important seasonal and interannual variations,
both in biomass and specific composition. As evidence of the species richness of
gelatinous plankton in the Alboran Sea, 58 species of planktonic Cnidaria and
Ctenophora were observed during a cruise in April 1991 off the North Moroccan
coast: 12 hydromedusae, 18 siphonophores, 6 scyphomedusae and 22 ctenophores
(Mills et al. 1996). The most abundant species in surface waters were Pandea conica
and Solmaris leucostyla (hydromedusae); Nanomia bijuga, Lensia conoidea and
Abylopsis tetragona (siphonophores); and Haeckelia beehleri, Pleurobrachia
rhodopis, Bolinopsis vitrea, Ocyropsis maculata and Beroe ovata (ctenophores).
The mesopelagic Solmissus albescens (Narcomedusae) was the most numerous
jellyfish in a wide bathymetric range capable of migrating to the surface at night.
A few species, such as the coronate scyphozoans Periphylla periphylla and
Paraphyllina ransoni and the siphonophore Rhizophysa filiformis, seemed to occur
mainly near the bottom (Mills et al. 1996). These authors have also noted a very rich
mesopelagic ctenophore fauna. Among them, Bathocyroe fosteri and
Thalassocalyce inconstans, originally known from the Atlantic, have been reported
in this westernmost area of the Mediterranean (Madin 1991).
The ubiquitous and troublesome scyphozoan Pelagia noctiluca (Fig. 10.15),
which appears to be blooming with increased frequency (Brotz and Pauly 2012),
deserves special mention. This holoplanktonic jellyfish inhabits oceanic as well as
coastal areas, being responsible for the majority of the stings suffered by bathers
(Canepa et al. 2014). Blooms of this medusa have been persistent in recent years in
the Andalusian coast, resulting in a large number of stings and in the temporary
closure of many beaches.
10 Invertebrates: The Realm of Diversity
395
recorded by these authors around this front are Subeucalanus monachus, Eucalanus
hyalinus, Clausocalanus furcatus and Centropages typicus.
Cladocerans, which exhibit a seasonal and/or aggregative distribution, are
represented by few species, but they can be very abundant in coastal waters, such
as Penilia avirostris, Pseudevadne tergestina, Evadne spinifera and E. nordmanni
(Rodríguez 1983). On the other hand, ostracods, which are not numerous in the
mesozooplankton communities at temperate latitudes, are more abundant in deep
waters than in the epipelagic zone (Siokou-Frangou et al. 2010).
The macroplankton of the Alboran Sea consists essentially of euphausiids,
chaetognaths and gelatinous zooplankton. According to Madin (1991), the dominant
euphausiid species occurring were Euphausia krohnii, Nematoscelis megalops,
Stylocheiron abbreviatum and S. suhmi, with maximum abundances in summer.
Chaetognaths are active predators and an important component of zooplankton.
They are well represented in the Alboran Sea by more than a dozen species (Camiñas
1985) that become very abundant in areas of higher biomass, such as in the vicinity
of the Almería-Oran Front. According to this author, the most abundant chaetognaths in the area are Parasagitta friderici, Serratosagitta tasmanica, Pterosagitta
draco, Flacisagitta enflata and Decipisagitta decipiens.
Three main phyla, the carnivorous Cnidaria and Ctenophora and the filterfeeding Tunicata, dominate the gelatinous macroplankton (Fig. 10.15). These
holoplanktonic organisms exhibit important seasonal and interannual variations,
both in biomass and specific composition. As evidence of the species richness of
gelatinous plankton in the Alboran Sea, 58 species of planktonic Cnidaria and
Ctenophora were observed during a cruise in April 1991 off the North Moroccan
coast: 12 hydromedusae, 18 siphonophores, 6 scyphomedusae and 22 ctenophores
(Mills et al. 1996). The most abundant species in surface waters were Pandea conica
and Solmaris leucostyla (hydromedusae); Nanomia bijuga, Lensia conoidea and
Abylopsis tetragona (siphonophores); and Haeckelia beehleri, Pleurobrachia
rhodopis, Bolinopsis vitrea, Ocyropsis maculata and Beroe ovata (ctenophores).
The mesopelagic Solmissus albescens (Narcomedusae) was the most numerous
jellyfish in a wide bathymetric range capable of migrating to the surface at night.
A few species, such as the coronate scyphozoans Periphylla periphylla and
Paraphyllina ransoni and the siphonophore Rhizophysa filiformis, seemed to occur
mainly near the bottom (Mills et al. 1996). These authors have also noted a very rich
mesopelagic ctenophore fauna. Among them, Bathocyroe fosteri and
Thalassocalyce inconstans, originally known from the Atlantic, have been reported
in this westernmost area of the Mediterranean (Madin 1991).
The ubiquitous and troublesome scyphozoan Pelagia noctiluca (Fig. 10.15),
which appears to be blooming with increased frequency (Brotz and Pauly 2012),
deserves special mention. This holoplanktonic jellyfish inhabits oceanic as well as
coastal areas, being responsible for the majority of the stings suffered by bathers
(Canepa et al. 2014). Blooms of this medusa have been persistent in recent years in
the Andalusian coast, resulting in a large number of stings and in the temporary
closure of many beaches.
10 Invertebrates: The Realm of Diversity
395