The Northern Atlantic Coasts
177
studies. No impact of eutrophication was found in these outer areas at
the start of the monitoring programme (Pedersen et al. 1991).
After the toxic algal bloom of the prymnesiophyte Chrysochromulina
polylepis in the late spring of 1988, a large number of localities along the
southern and southwestern coasts were investigated for effects of the
bloom on the hard-bottom communities (e.g. Berge et al. 1988; Pedersen
et al. 1989). The main effects were about the same as on the Swedish west
coast. In 1990, almost normal community composition was reported for
those areas with an increase in the number of macroalgal species occurring compared to the period directly after the bloom (Pedersen et al.
1991).
Changes in the macroalgal communities have also been caused by
introduced species (e.g. Rueness 1989; Wallentinus in press), the most
prominent being that of the Japanese brown alga Sargassum muticum. It
was first reported as drift plants in southern Norway in 1984, and in 1988
the first attached plants were found (Rueness 1989 and references therein). During 1989 it grew attached at several new localities along the
Norwegian coast of Skagerrak, from west of the mouth of the Oslofjord
in the east, to as far west as MandaI, occurring partly in large quantities
and reaching sizes of 1-2 m (Rueness 1990). Rueness stated that it
mainly occupies areas where other species of the Fucales are less well
developed, and that it can be a nuisance in marinas and recreation areas.
He also predicted its further dispersal along the Norwegian coast towards
north and east, including into the inner Oslofjord, where so far only drift
plants had been found. In 1993, it was reported growing at the island of
Herdla outside Bergen on the west coast (T. Lein and J. Rueness, pers.
comm.).
Experimental studies of the impact of fish farming (discharges of
nutrients and warm-water effluents) have been carried out showing that
both the metabolism of the algae and the community structure were
influenced by the heated water and that the effects were accentuated
(synergistic or antagonistic effects) when combined with nutrients
(Pedersen et al. 1992).
6.4.1 The Oslo Fjord
Along the Norwegian south coast, the most well-known area with respect
to changes in macroalgal communities is that of the Oslo Fjord. Especially the inner part of this fjord has been extensively studied (for references
see Bokn et al. 1992). They referred to reports on macro algae in this area
dating back 100 years from which it can be concluded that Fucus
177
studies. No impact of eutrophication was found in these outer areas at
the start of the monitoring programme (Pedersen et al. 1991).
After the toxic algal bloom of the prymnesiophyte Chrysochromulina
polylepis in the late spring of 1988, a large number of localities along the
southern and southwestern coasts were investigated for effects of the
bloom on the hard-bottom communities (e.g. Berge et al. 1988; Pedersen
et al. 1989). The main effects were about the same as on the Swedish west
coast. In 1990, almost normal community composition was reported for
those areas with an increase in the number of macroalgal species occurring compared to the period directly after the bloom (Pedersen et al.
1991).
Changes in the macroalgal communities have also been caused by
introduced species (e.g. Rueness 1989; Wallentinus in press), the most
prominent being that of the Japanese brown alga Sargassum muticum. It
was first reported as drift plants in southern Norway in 1984, and in 1988
the first attached plants were found (Rueness 1989 and references therein). During 1989 it grew attached at several new localities along the
Norwegian coast of Skagerrak, from west of the mouth of the Oslofjord
in the east, to as far west as MandaI, occurring partly in large quantities
and reaching sizes of 1-2 m (Rueness 1990). Rueness stated that it
mainly occupies areas where other species of the Fucales are less well
developed, and that it can be a nuisance in marinas and recreation areas.
He also predicted its further dispersal along the Norwegian coast towards
north and east, including into the inner Oslofjord, where so far only drift
plants had been found. In 1993, it was reported growing at the island of
Herdla outside Bergen on the west coast (T. Lein and J. Rueness, pers.
comm.).
Experimental studies of the impact of fish farming (discharges of
nutrients and warm-water effluents) have been carried out showing that
both the metabolism of the algae and the community structure were
influenced by the heated water and that the effects were accentuated
(synergistic or antagonistic effects) when combined with nutrients
(Pedersen et al. 1992).
6.4.1 The Oslo Fjord
Along the Norwegian south coast, the most well-known area with respect
to changes in macroalgal communities is that of the Oslo Fjord. Especially the inner part of this fjord has been extensively studied (for references
see Bokn et al. 1992). They referred to reports on macro algae in this area
dating back 100 years from which it can be concluded that Fucus