10.4 The Invertebrates of the Water Column
10.4.1 Planktonic Invertebrates
The peculiar and contrasting hydrological characteristics of the Alboran Sea are
reflected in the structure and dynamics of plankton communities, which have been
the object of many researches and publications. Several articles concern the specific
composition and population assemblages of zooplankton in the Alboran Sea
(e.g. Vives et al. 1975; Rodríguez 1983; Greze et al. 1985; Champalbert 1996;
Youssara and Gaudy 2001; Andersen et al. 2004; Siokou-Frangou et al. 2010). In
fact, nearly 30 years ago, a literature review and field guide of zooplankton of this
area was already published by the Woods Hole Oceanographic Institution (Madin
1991).
While microzooplankton is mainly composed by protists (flagellates, dinoflagellates, ciliates, radiolarians, foraminiferans, among others), the invertebrates are the
main component of mesozooplankton (size range of 0.2–2 mm) and macroplankton
(organisms visible to the naked eye). Epipelagic mesozooplankton is highly diversified in terms of taxonomic composition. In addition to the strictly planktonic
groups (holozooplankton), the pelagic larval phases of many invertebrates which
are benthic in their adult phase are also incorporated to the plankton
(merozooplankton). As elsewhere, copepods represent the largest group in the
Alboran Sea both in terms of abundance and biomass (about 60% of the biomass),
followed by cladocerans (near 20%) and larvae of various groups (about 12%,
mainly crustaceans and molluscs).
More than 250 species of copepods have been recorded in the Alboran Sea. A few
small-sized and species-rich genera of calanoids (Clausocalanus, Calocalanus,
Pleuromamma and Temora, together with Ctenocalanus vanus) and cyclopoids
(Oithona, Oncaea) account for the bulk of copepod abundance and biomass in
epipelagic layers (Seguin et al. 1994; Youssara and Gaudy 2001; Siokou-Frangou
et al. 2010). According to Rodríguez (1983), the most abundant copepods reported
in spring in the upper layer were Paracalanus parvus, Clausocalanus arcuicornis,
Centropages chierchiae, Acartia clausi, Temora stylifera, Oithona similis, O. nana
and Oncaea spp. Some species seem particularly linked to Atlantic waters, such as
Pleuromamma borealis, Subeucalanus crassus, Eucalanus elongatus or Triconia
dentipes (Youssara and Gaudy 2001). Otherwise, two copepod species were
described from the Alboran Sea by Shmeleva (1979): Oncaea alboranica and
Calocalanus alboranus.
In the neuston layer, pontellids often constitute the major diurnal biomass.
Among the most abundant species, Anomalocera patersoni, Pontella lobiancoi,
P. atlantica and Pontellopsis regalis have an Atlantic origin and are abundant in
oceanic waters, whereas Pontella mediterranea and Labidocera wollastoni are rather
neritic species (Champalbert 1996).
Across the Almería-Oran Front area, three species of Pleuromamma were found
in large numbers: P. borealis, the most abundant, followed by P. abdominalis and to
394
J. Templado et al.
10.4.1 Planktonic Invertebrates
The peculiar and contrasting hydrological characteristics of the Alboran Sea are
reflected in the structure and dynamics of plankton communities, which have been
the object of many researches and publications. Several articles concern the specific
composition and population assemblages of zooplankton in the Alboran Sea
(e.g. Vives et al. 1975; Rodríguez 1983; Greze et al. 1985; Champalbert 1996;
Youssara and Gaudy 2001; Andersen et al. 2004; Siokou-Frangou et al. 2010). In
fact, nearly 30 years ago, a literature review and field guide of zooplankton of this
area was already published by the Woods Hole Oceanographic Institution (Madin
1991).
While microzooplankton is mainly composed by protists (flagellates, dinoflagellates, ciliates, radiolarians, foraminiferans, among others), the invertebrates are the
main component of mesozooplankton (size range of 0.2–2 mm) and macroplankton
(organisms visible to the naked eye). Epipelagic mesozooplankton is highly diversified in terms of taxonomic composition. In addition to the strictly planktonic
groups (holozooplankton), the pelagic larval phases of many invertebrates which
are benthic in their adult phase are also incorporated to the plankton
(merozooplankton). As elsewhere, copepods represent the largest group in the
Alboran Sea both in terms of abundance and biomass (about 60% of the biomass),
followed by cladocerans (near 20%) and larvae of various groups (about 12%,
mainly crustaceans and molluscs).
More than 250 species of copepods have been recorded in the Alboran Sea. A few
small-sized and species-rich genera of calanoids (Clausocalanus, Calocalanus,
Pleuromamma and Temora, together with Ctenocalanus vanus) and cyclopoids
(Oithona, Oncaea) account for the bulk of copepod abundance and biomass in
epipelagic layers (Seguin et al. 1994; Youssara and Gaudy 2001; Siokou-Frangou
et al. 2010). According to Rodríguez (1983), the most abundant copepods reported
in spring in the upper layer were Paracalanus parvus, Clausocalanus arcuicornis,
Centropages chierchiae, Acartia clausi, Temora stylifera, Oithona similis, O. nana
and Oncaea spp. Some species seem particularly linked to Atlantic waters, such as
Pleuromamma borealis, Subeucalanus crassus, Eucalanus elongatus or Triconia
dentipes (Youssara and Gaudy 2001). Otherwise, two copepod species were
described from the Alboran Sea by Shmeleva (1979): Oncaea alboranica and
Calocalanus alboranus.
In the neuston layer, pontellids often constitute the major diurnal biomass.
Among the most abundant species, Anomalocera patersoni, Pontella lobiancoi,
P. atlantica and Pontellopsis regalis have an Atlantic origin and are abundant in
oceanic waters, whereas Pontella mediterranea and Labidocera wollastoni are rather
neritic species (Champalbert 1996).
Across the Almería-Oran Front area, three species of Pleuromamma were found
in large numbers: P. borealis, the most abundant, followed by P. abdominalis and to
394
J. Templado et al.