268
F.X. Niell et al.
The southern Atlantic region is a continuation of the Portuguese
coast, extending into the Mediterranean to the mid coast of Malaga.
Conde (1981) gives evidence for the delimitation of this region. Among
other aspects, it is defined by the presence of Fucus spiralis on the
Mediterranean coast, the existence of slight tidal movements and by the
limit of distribution of the seagrass Posidonia oceanica, a Mediterranean
endemic species, the frontier of which coincides with the previously
mentioned eastern distribution of F. spiralis. For these reasons, the Strait
of Gibraltar is not really a biogeographical frontier, as Fisher-Piette
(I959b) pointed out in his classical and interesting descriptions. The
political frontier between Spain and Portugal is also biogeographically
irrelevant. This is specially evident due to the presence of Atlantic
surface water that enters the Alboran Sea.
In this area there are interesting salt marshes (Doiiana, Cadiz Bay,
Barbate and Palmones-Algeciras), which, despite their characteristic of
being natural bird sanctuaries, are very polluted due to discharge of
urban and industrial effluents. The Romans, during the colonization,
used to catch fish in these areas by means of controlling the outflow of
tidal water in special closed constructions ("esteros"), which were
opened at high tide to allow fish to enter. The outflowing water was
sieved using nets. These structures were connected by means of a complicated system of channels, and are, together with the salt brine ponds,
frequent in many parts of the area. All along this coast there are small
shallow tidal estuaries.
This region presents clear differences compared to the northern and
north-western coasts. Summer air temperature (close to 40°C), as well as
irradiance, is high, and irregular input of nutrients related to stormy and
unpredictable rains or to very changeable strong winds in the area of the
Strait of Gibraltar is typical. The tidal amplitude is very small with a
maximal oscillation of 1 m (Niell et al. 1989), and the emersion period is
usually long, obviously causing stress for plants and animals.
10.2 Macroalgal Proliferation
Along the Spanish Atlantic Coasts
Until now, no important or catastrophic occurrence of algal masses has
been found along the Spanish Atlantic coast. Yearly observations in the
Ria of Vigo and in the southern Atlantic region detected only local proliferations of green algae, which have never attained the enviornmental
F.X. Niell et al.
The southern Atlantic region is a continuation of the Portuguese
coast, extending into the Mediterranean to the mid coast of Malaga.
Conde (1981) gives evidence for the delimitation of this region. Among
other aspects, it is defined by the presence of Fucus spiralis on the
Mediterranean coast, the existence of slight tidal movements and by the
limit of distribution of the seagrass Posidonia oceanica, a Mediterranean
endemic species, the frontier of which coincides with the previously
mentioned eastern distribution of F. spiralis. For these reasons, the Strait
of Gibraltar is not really a biogeographical frontier, as Fisher-Piette
(I959b) pointed out in his classical and interesting descriptions. The
political frontier between Spain and Portugal is also biogeographically
irrelevant. This is specially evident due to the presence of Atlantic
surface water that enters the Alboran Sea.
In this area there are interesting salt marshes (Doiiana, Cadiz Bay,
Barbate and Palmones-Algeciras), which, despite their characteristic of
being natural bird sanctuaries, are very polluted due to discharge of
urban and industrial effluents. The Romans, during the colonization,
used to catch fish in these areas by means of controlling the outflow of
tidal water in special closed constructions ("esteros"), which were
opened at high tide to allow fish to enter. The outflowing water was
sieved using nets. These structures were connected by means of a complicated system of channels, and are, together with the salt brine ponds,
frequent in many parts of the area. All along this coast there are small
shallow tidal estuaries.
This region presents clear differences compared to the northern and
north-western coasts. Summer air temperature (close to 40°C), as well as
irradiance, is high, and irregular input of nutrients related to stormy and
unpredictable rains or to very changeable strong winds in the area of the
Strait of Gibraltar is typical. The tidal amplitude is very small with a
maximal oscillation of 1 m (Niell et al. 1989), and the emersion period is
usually long, obviously causing stress for plants and animals.
10.2 Macroalgal Proliferation
Along the Spanish Atlantic Coasts
Until now, no important or catastrophic occurrence of algal masses has
been found along the Spanish Atlantic coast. Yearly observations in the
Ria of Vigo and in the southern Atlantic region detected only local proliferations of green algae, which have never attained the enviornmental