Spanish Atlantic Coasts
269
importance that they have had in the shallow coastal platforms of
Brittany, the Netherlands, Germany or Denmark.
A survey within a group of phycologists working in different places
along the Spanish Atlantic coast revealed that macroalgal proliferations
are very scarce. Despite this, some local proliferations in the inner part
of the Rias during summer have had catastrophic effects on the populations of bivalves of commercial interest.
The main species that cause proliferations in these areas belong to the
Ulvaceae. Data are available from studies made on algal community
structure and succession. Of these, three studies have been selected to
compare the behaviour of the Ulvaceae in the three coastal areas; Fernandez (1980) for the Cantabric area (A), Niell (1976) and several subsequent papers published on the Rias Bajas of the northwestern area (B),
and Niell et al. (1989) for the definition of some characteristics of the
communities of the Strait of Gibraltar (C).
Proliferations of seaweed of the Ulva type are associated with increase
of nitrogen in the environment. Ulvaceae are typical opportunistic
species. The filamentous and ramified species of Enteromorpha
(E. compressa and E. prolifera) are replaced in summer by E. ramulosa, E.
multiramosa and/or E. clathrata. They are most resistant to emersion
than the species of Ulva (U. rigida, U. curvata and U.cf.gigantea), which
are mainly present at low levels of the intertidal system.
In the Cantabric area, the presence of Enteromorpha on the rocky
shores is very irregular, with sparse populations and very low biomass (Fig
10.2). The biomass of Ulva reached maximal values of 30 g dry weight per
m 2 in July (Fernandez 1980), whereas Fuentes (1986) found a maximal
biomass of 24 g dry weight per m 2 of Ulva at the level of Fucus vesiculosus
in Ria of Arousa (northwestern area), values very similar to those obtained
by Niell (1976) at the level of Himanthalia, 23.4 g dry weight m -2.
A presumed polluted area close to a pulp kraft mill factory was also
studied in the Ria of Pontevedra (NielI1974; Niell and Buela 1976; Niell
and Paz6 1978). Around the source of pollution, a nearly abiotic area was
found where only some sulfur bacteria lived. Macrophytic vegetation
increased with increasing distance from the point of discharge. In this
area, the biomass of Ulvaceae was higher compared to other Rias
(Fig 10.3). Waste freshwater of industrial and urban origin caused the
presence of green patches in the intertidal system, without the typical
Fucacean dominance. In this area, the biomass of Enteromorpha was
higher than the biomass of Ulva.
Data are more scarce in the southern Atlantic region of Spain, and
most of them are part of studies on recuperation of cleaned surfaces
(Espejo 1984). Figures presented in this study are computed from small
269
importance that they have had in the shallow coastal platforms of
Brittany, the Netherlands, Germany or Denmark.
A survey within a group of phycologists working in different places
along the Spanish Atlantic coast revealed that macroalgal proliferations
are very scarce. Despite this, some local proliferations in the inner part
of the Rias during summer have had catastrophic effects on the populations of bivalves of commercial interest.
The main species that cause proliferations in these areas belong to the
Ulvaceae. Data are available from studies made on algal community
structure and succession. Of these, three studies have been selected to
compare the behaviour of the Ulvaceae in the three coastal areas; Fernandez (1980) for the Cantabric area (A), Niell (1976) and several subsequent papers published on the Rias Bajas of the northwestern area (B),
and Niell et al. (1989) for the definition of some characteristics of the
communities of the Strait of Gibraltar (C).
Proliferations of seaweed of the Ulva type are associated with increase
of nitrogen in the environment. Ulvaceae are typical opportunistic
species. The filamentous and ramified species of Enteromorpha
(E. compressa and E. prolifera) are replaced in summer by E. ramulosa, E.
multiramosa and/or E. clathrata. They are most resistant to emersion
than the species of Ulva (U. rigida, U. curvata and U.cf.gigantea), which
are mainly present at low levels of the intertidal system.
In the Cantabric area, the presence of Enteromorpha on the rocky
shores is very irregular, with sparse populations and very low biomass (Fig
10.2). The biomass of Ulva reached maximal values of 30 g dry weight per
m 2 in July (Fernandez 1980), whereas Fuentes (1986) found a maximal
biomass of 24 g dry weight per m 2 of Ulva at the level of Fucus vesiculosus
in Ria of Arousa (northwestern area), values very similar to those obtained
by Niell (1976) at the level of Himanthalia, 23.4 g dry weight m -2.
A presumed polluted area close to a pulp kraft mill factory was also
studied in the Ria of Pontevedra (NielI1974; Niell and Buela 1976; Niell
and Paz6 1978). Around the source of pollution, a nearly abiotic area was
found where only some sulfur bacteria lived. Macrophytic vegetation
increased with increasing distance from the point of discharge. In this
area, the biomass of Ulvaceae was higher compared to other Rias
(Fig 10.3). Waste freshwater of industrial and urban origin caused the
presence of green patches in the intertidal system, without the typical
Fucacean dominance. In this area, the biomass of Enteromorpha was
higher than the biomass of Ulva.
Data are more scarce in the southern Atlantic region of Spain, and
most of them are part of studies on recuperation of cleaned surfaces
(Espejo 1984). Figures presented in this study are computed from small