The Northern Atlantic Coasts
169
grasses (mainly Zostera marina, but species of the genera Ruppia and
Zannichellia are also common).
Although consisting of fewer species, the algal zonation in the littoral
and sublittoral belts is roughly the same as on the northern Atlantic
shores (e.g. Soderstrom 1965; Wrern 1965), except for the laminarians
which are closely restricted to the sublittoral zone as is Fucus serratus.
Many species also are reduced in size, a phenomenon more accentuated the further one approaches the Baltic (e.g. Wrern 1965; Wallentinus 1991). In comparison to the fully marine Atlantic shores, the marine flora thus is somewhat impoverished, even in areas not affected by
pollution. Several factors are responsible. The reduced salinity, caused by
the outflow of the Baltic water and in some regions also by the many
rivers, is one of the main reasons for this reduction in number of species.
But also higher water temperatures are responsible for the lack of some
species (see e.g. Sundene 1962). Prominent species missing are brown
algae such as Pelvetia canaliculata, Fucus ceranoides (cf. Back et al.
1992), Himanthalia elongata, Saccorhiza polyschides (see Norton 1977)
and Alaria esculenta (cf. Sundene 1962), and the red alga Mastocarpus
stellata, while others occur in the area only rarely (see e.g. species listed
by Wrern 1958, 1961; Karlsson et al. 1992a).
For the Swedish west coast, monitoring studies which include the
seaweed communities have been carried out only on a pilot scale since
1989 (Karlsson et al. 1992b). Before, only temporary research projects
were performed. Within this programme changes in macro algal vegetation have been analyzed statistically in time and space. However, unfortunately, we still have too poor a knowledge of the quantitative response
of the macroalgal communities to a particular load of nutrients. This is
especially true for the effects of altered balance between nitrogen and
phosphorus as well as for the role of trace elements.
Introduced species have changed the macro algal communities in this
area during the last century, too (e.g. Karlsson et al. 1992a; Wallentinus,
in press). During the last decade, the Japanese brown alga Sargassum
muticum was first found attached in the northern part of the province of
Bohuslan in 1987. Now in the early 1990s, it grows along many of the
shores of the Skagerrak, from the Norwegian border southwards to the
Goteborg archipelago, the northern Kattegat (Karlsson et al. 1992a). They
also reported that it has locally started to be a nuisance to recreation and
fishery, but so far it has not outcompeted native algal species.
Other events also influence the composition of the algal vegetation.
The toxic bloom of the prymnesiophyte Chrysochromulina polylepis in
the late spring of 1988 had an impact on several macro algae, mainly red
and some green algae, in both the Skagerrak and the Kattegat area (e.g.
169
grasses (mainly Zostera marina, but species of the genera Ruppia and
Zannichellia are also common).
Although consisting of fewer species, the algal zonation in the littoral
and sublittoral belts is roughly the same as on the northern Atlantic
shores (e.g. Soderstrom 1965; Wrern 1965), except for the laminarians
which are closely restricted to the sublittoral zone as is Fucus serratus.
Many species also are reduced in size, a phenomenon more accentuated the further one approaches the Baltic (e.g. Wrern 1965; Wallentinus 1991). In comparison to the fully marine Atlantic shores, the marine flora thus is somewhat impoverished, even in areas not affected by
pollution. Several factors are responsible. The reduced salinity, caused by
the outflow of the Baltic water and in some regions also by the many
rivers, is one of the main reasons for this reduction in number of species.
But also higher water temperatures are responsible for the lack of some
species (see e.g. Sundene 1962). Prominent species missing are brown
algae such as Pelvetia canaliculata, Fucus ceranoides (cf. Back et al.
1992), Himanthalia elongata, Saccorhiza polyschides (see Norton 1977)
and Alaria esculenta (cf. Sundene 1962), and the red alga Mastocarpus
stellata, while others occur in the area only rarely (see e.g. species listed
by Wrern 1958, 1961; Karlsson et al. 1992a).
For the Swedish west coast, monitoring studies which include the
seaweed communities have been carried out only on a pilot scale since
1989 (Karlsson et al. 1992b). Before, only temporary research projects
were performed. Within this programme changes in macro algal vegetation have been analyzed statistically in time and space. However, unfortunately, we still have too poor a knowledge of the quantitative response
of the macroalgal communities to a particular load of nutrients. This is
especially true for the effects of altered balance between nitrogen and
phosphorus as well as for the role of trace elements.
Introduced species have changed the macro algal communities in this
area during the last century, too (e.g. Karlsson et al. 1992a; Wallentinus,
in press). During the last decade, the Japanese brown alga Sargassum
muticum was first found attached in the northern part of the province of
Bohuslan in 1987. Now in the early 1990s, it grows along many of the
shores of the Skagerrak, from the Norwegian border southwards to the
Goteborg archipelago, the northern Kattegat (Karlsson et al. 1992a). They
also reported that it has locally started to be a nuisance to recreation and
fishery, but so far it has not outcompeted native algal species.
Other events also influence the composition of the algal vegetation.
The toxic bloom of the prymnesiophyte Chrysochromulina polylepis in
the late spring of 1988 had an impact on several macro algae, mainly red
and some green algae, in both the Skagerrak and the Kattegat area (e.g.