Introduction to the Marine Algae: Overview 13
algae (e.g., Bangia). The intermediate zone (mid shore) is characterized by three horizontal bands:
the upper one containing barnacles (Chthamalus, Semibalanus), mussels (Mytilus), some Chlorophyta
(Blidingia), and some brown algae (e.g., Pelvetia, Fucus distichus, Ralfsia); the mid band still containing
littorinids and barnacles, but dominated by Fucus vesiculosus, Ascophyllum nodosum, Hildenbrandia,
and Porphyra; and finally the lower band which is totally dominated by algae, namely Fucus serratus,
Mastocarpus stellatus, Chondrus crispus, corallines, Ulva, Cladophora rupestris, and seasonally
Dumontia and Scytosiphon. The lower intertidal zone (low shore) is dominated by the red Palmaria
palmata and several Laminaria species. At these northern latitudes, the Fucales distribution follows a
gradation with Pelvetia appearing higher on the coast, followed by Fucus spiralis, F. vesiculosus, and
F. serratus, and then Laminaria digitata and L. hyperborea (Johnson et al. 1998).
The dense mats of fucoids influence the structure and functioning of communities because these large
algae provide available colonization area to numerous epiphytes; they also offer these epiphytes protection
against desiccation and hydrodynamism. Consequently, fucoids dominated communities support multiple
herbivores, including mollusks, barnacles, and echinoderms. In the rocky shores of northern Europe,
algae and barnacles share dominance and the algal growth is the main factor influencing the coastal
ecology (Hawkins and Hartnoll 1983; Jenkins et al. 2004). The transition between the intertidal and
subtidal communities in temperate and cold North Atlantic is marked by the presence of kelps, species
of Laminariales, predominantly Laminaria, Alaria, Ecklonia, Nereocystis, and Macrocystis. These algae
extend their distribution to lower subtidal levels, where they can form extensive submerged forests,
depending on water clarity. Kelps are globally important foundation species that occupy coastlines of
all continents except Antarctica. Kelps are among the most productive primary producers on the planet,
and greatly enhance diversity and secondary productivity locally by forming habitat for many other
species, including those that support commercial fisheries (Bertocci et al. 2016). Sea urchins are often the
structuring organisms of these forests and can cause deforestations (called sea urchin barrens) when their
populations expand, eliminating all large seaweeds from considerable areas. Kelp forests are receding in
many coastal areas in Europe (Araújo et al. 2016) and globally (Krumhansl et al. 2016) mostly due to
climate change and other stresses.
Benthic communities of warm temperate and subtropical waters
The intertidal algal communities in warm temperate and subtropical waters are characterized by some
basic differences in relation to the ones from temperate and cold waters especially with regard to the
absence of the large Laminariales. This is the situation of the Macaronesian Region composed of the
Atlantic islands of Azores, Madeira, the Canaries, and Cape Verde (Fig. 5).
The Macaronesia seems to represent a bridge between Northern Europe, the Mediterranean, and the
tropical and subtropical coasts further south. Many cold-water species in this region have their southern
limit of distribution, while others have their northern limit of occurrence here.
The typical intertidal zonation at these latitudes is characterized by the presence of three main zones
(Neto et al. 2005). Higher in the shore is a zone characterized by animals (winkles, Littorina spp., Fig. 6A)
with the marine lichen Lichina confinis and the Cyanobacteria Rivularia sporadically present. The upper
mid shore zone is characterized by a patchy mosaic of animals (mainly barnacles) and algae (principally
Fucus spiralis, Gelidium microdon, and Caulacanthus ustulatus, Fig. 6B). The lower part of this zone is
characterized by algal turf, a growth of either diminutive algae or diminutive forms of larger species that
create a dense, compact mat 20–30 mm thick often covering large areas of rock (Fig. 6C). Turfs may be
monospecific or contain numerous species and may be characterized by articulated calcareous algae such
as Elisolandia and Jania, or by soft algae such as Ceramium, Chondracanthus, and Osmundea. The lower
level (low shore) is dominated by the larger, erect, corticated macrophytes (Pterocladiella capillacea,
Cystoseira abies-marina, Halopteris scoparia) and articulated calcareous algae.
As in Northern latitudes, seaweed communities create a suitable habitat for many small invertebrates
that live among algal thalli or within the algal turf. The more common herbivorous are the limpets that
graze on the microscopic germling algal stages, and the sea-urchins.
algae (e.g., Bangia). The intermediate zone (mid shore) is characterized by three horizontal bands:
the upper one containing barnacles (Chthamalus, Semibalanus), mussels (Mytilus), some Chlorophyta
(Blidingia), and some brown algae (e.g., Pelvetia, Fucus distichus, Ralfsia); the mid band still containing
littorinids and barnacles, but dominated by Fucus vesiculosus, Ascophyllum nodosum, Hildenbrandia,
and Porphyra; and finally the lower band which is totally dominated by algae, namely Fucus serratus,
Mastocarpus stellatus, Chondrus crispus, corallines, Ulva, Cladophora rupestris, and seasonally
Dumontia and Scytosiphon. The lower intertidal zone (low shore) is dominated by the red Palmaria
palmata and several Laminaria species. At these northern latitudes, the Fucales distribution follows a
gradation with Pelvetia appearing higher on the coast, followed by Fucus spiralis, F. vesiculosus, and
F. serratus, and then Laminaria digitata and L. hyperborea (Johnson et al. 1998).
The dense mats of fucoids influence the structure and functioning of communities because these large
algae provide available colonization area to numerous epiphytes; they also offer these epiphytes protection
against desiccation and hydrodynamism. Consequently, fucoids dominated communities support multiple
herbivores, including mollusks, barnacles, and echinoderms. In the rocky shores of northern Europe,
algae and barnacles share dominance and the algal growth is the main factor influencing the coastal
ecology (Hawkins and Hartnoll 1983; Jenkins et al. 2004). The transition between the intertidal and
subtidal communities in temperate and cold North Atlantic is marked by the presence of kelps, species
of Laminariales, predominantly Laminaria, Alaria, Ecklonia, Nereocystis, and Macrocystis. These algae
extend their distribution to lower subtidal levels, where they can form extensive submerged forests,
depending on water clarity. Kelps are globally important foundation species that occupy coastlines of
all continents except Antarctica. Kelps are among the most productive primary producers on the planet,
and greatly enhance diversity and secondary productivity locally by forming habitat for many other
species, including those that support commercial fisheries (Bertocci et al. 2016). Sea urchins are often the
structuring organisms of these forests and can cause deforestations (called sea urchin barrens) when their
populations expand, eliminating all large seaweeds from considerable areas. Kelp forests are receding in
many coastal areas in Europe (Araújo et al. 2016) and globally (Krumhansl et al. 2016) mostly due to
climate change and other stresses.
Benthic communities of warm temperate and subtropical waters
The intertidal algal communities in warm temperate and subtropical waters are characterized by some
basic differences in relation to the ones from temperate and cold waters especially with regard to the
absence of the large Laminariales. This is the situation of the Macaronesian Region composed of the
Atlantic islands of Azores, Madeira, the Canaries, and Cape Verde (Fig. 5).
The Macaronesia seems to represent a bridge between Northern Europe, the Mediterranean, and the
tropical and subtropical coasts further south. Many cold-water species in this region have their southern
limit of distribution, while others have their northern limit of occurrence here.
The typical intertidal zonation at these latitudes is characterized by the presence of three main zones
(Neto et al. 2005). Higher in the shore is a zone characterized by animals (winkles, Littorina spp., Fig. 6A)
with the marine lichen Lichina confinis and the Cyanobacteria Rivularia sporadically present. The upper
mid shore zone is characterized by a patchy mosaic of animals (mainly barnacles) and algae (principally
Fucus spiralis, Gelidium microdon, and Caulacanthus ustulatus, Fig. 6B). The lower part of this zone is
characterized by algal turf, a growth of either diminutive algae or diminutive forms of larger species that
create a dense, compact mat 20–30 mm thick often covering large areas of rock (Fig. 6C). Turfs may be
monospecific or contain numerous species and may be characterized by articulated calcareous algae such
as Elisolandia and Jania, or by soft algae such as Ceramium, Chondracanthus, and Osmundea. The lower
level (low shore) is dominated by the larger, erect, corticated macrophytes (Pterocladiella capillacea,
Cystoseira abies-marina, Halopteris scoparia) and articulated calcareous algae.
As in Northern latitudes, seaweed communities create a suitable habitat for many small invertebrates
that live among algal thalli or within the algal turf. The more common herbivorous are the limpets that
graze on the microscopic germling algal stages, and the sea-urchins.