Spanish Atlantic Coasts
267
open marine coast to the inner shallow estuarine waters. In this region
there are relics of some seaweeds very abundant in Northern European
waters, such as Ascophyllum nodosum, Fucus serratus, Chorda filum and
dwarf forms of Fucus vesiculosus (Niell et al. 1980a). The estuaries in the
northern coast of this region are smaller than the Rias Bajas, and are
named Rias Altas. Despite this coincidence in their denomination, no
similarities in their hydrographical features can be found between these
northern and western estuaries. Rias Altas look like the estuaries of the
Cantabric region, but the dominant species of their flora are different.
The northwestern area was studied in recurrent yearly surveys by
some classical phycologists. Among them, the works of Fisher-Piette
(1955a,b, 1956, 1957a, b, 1958, 1959a, 1963) are very interesting because
he followed faunistic and floristic changes from the end of World War II
to the seventies. Fisher-Piette (op. cit.) stated that the organisms living in
this "corner" are similar to those found on the coasts of French Britanny
and used the term "septentrionalization" to refer to the boreal aspect of
the algal communities at the biogeographical discontinuity found in
Galicia, in contrast to the Portuguese and Cantabric floras. The southern
frontier of this "septentrionalized" area is located 40 Km south of the
geographical border between Spain and Portugal (Ardre 1970, 1971), in
the river Limia (Fig. 10.1).
The Rias are, in some ways, unique systems. Their geological formation has been recurrently studied since the early works of Scheu (1913)
to those of Brongersma and Pannekoek (1966) and Pannekoek (1966
a,b). The water circulation in the Rias has also been studied by a plethora
of oceanographers. Among them, Saiz and coworkers (1961a,b) and
Mouriiio et al. (1984) studied the Ria of Vigo, Otto (1975) the Ria of
Arousa, and Figueiras et al. (1985) the Ria of Pontevedra. All these works
are fundamental for the understanding of the circulation in the Rias,
which is not simple, because the estuarine system is influenced by
external coastal water movements and sometimes by the Central North
Atlantic water, running offshore southwards. Inflow of water into the
Rias causes fertilization processes. In addition, a cold upwelling occurs
during summer which has also effects on nutrient supply and productivity (Fraga 1979) and is related to the floristic discontinuity found
here with abundant presence of the northern flora and fauna species
(Niell et al. 1980b; Anad6n and Niell1981).
Ardre and coworkers (1958) made the first attempt to relate the
distribution of benthic organisms to the environmental variables in the
Rias. Since that first study, numerous investigations have been made on
different communities and organisms. The dynamics of the algal communities have been studied by Niell (1977).
267
open marine coast to the inner shallow estuarine waters. In this region
there are relics of some seaweeds very abundant in Northern European
waters, such as Ascophyllum nodosum, Fucus serratus, Chorda filum and
dwarf forms of Fucus vesiculosus (Niell et al. 1980a). The estuaries in the
northern coast of this region are smaller than the Rias Bajas, and are
named Rias Altas. Despite this coincidence in their denomination, no
similarities in their hydrographical features can be found between these
northern and western estuaries. Rias Altas look like the estuaries of the
Cantabric region, but the dominant species of their flora are different.
The northwestern area was studied in recurrent yearly surveys by
some classical phycologists. Among them, the works of Fisher-Piette
(1955a,b, 1956, 1957a, b, 1958, 1959a, 1963) are very interesting because
he followed faunistic and floristic changes from the end of World War II
to the seventies. Fisher-Piette (op. cit.) stated that the organisms living in
this "corner" are similar to those found on the coasts of French Britanny
and used the term "septentrionalization" to refer to the boreal aspect of
the algal communities at the biogeographical discontinuity found in
Galicia, in contrast to the Portuguese and Cantabric floras. The southern
frontier of this "septentrionalized" area is located 40 Km south of the
geographical border between Spain and Portugal (Ardre 1970, 1971), in
the river Limia (Fig. 10.1).
The Rias are, in some ways, unique systems. Their geological formation has been recurrently studied since the early works of Scheu (1913)
to those of Brongersma and Pannekoek (1966) and Pannekoek (1966
a,b). The water circulation in the Rias has also been studied by a plethora
of oceanographers. Among them, Saiz and coworkers (1961a,b) and
Mouriiio et al. (1984) studied the Ria of Vigo, Otto (1975) the Ria of
Arousa, and Figueiras et al. (1985) the Ria of Pontevedra. All these works
are fundamental for the understanding of the circulation in the Rias,
which is not simple, because the estuarine system is influenced by
external coastal water movements and sometimes by the Central North
Atlantic water, running offshore southwards. Inflow of water into the
Rias causes fertilization processes. In addition, a cold upwelling occurs
during summer which has also effects on nutrient supply and productivity (Fraga 1979) and is related to the floristic discontinuity found
here with abundant presence of the northern flora and fauna species
(Niell et al. 1980b; Anad6n and Niell1981).
Ardre and coworkers (1958) made the first attempt to relate the
distribution of benthic organisms to the environmental variables in the
Rias. Since that first study, numerous investigations have been made on
different communities and organisms. The dynamics of the algal communities have been studied by Niell (1977).