180
1. Wallentinus
to the threshold at about 100 m, and deep water below. High nutrient
concentrations could be measured in the surface layer as far as 10 km
from the discharge, being highest on the northern side of the fjord, and
even 25 km from the discharge there were indications of somewhat
increased nutrient levels. Reduced oxygen levels were measured in the
deep water in late summer.
Molvrer and Knutzen found an almost total dominance of green algal
associations (species of Ulothrix, Enteromorpha and Urospora) in the
littoral zone along 4-5 km on the northern side. Fucoids were absent,
whereas they occurred in the fjord inside the point of discharge. In
addition, the filter-feeding Semibalanus balanoides and Mytilus edulis
were present in large amounts, probably being favoured by high plankton concentrations and partly competing for space with the algae. Nitrogen and phosphorus content in the fucoid tissues were also increased at
stations where the nutrient concentrations were high and showed a linear
correlation with the concentrations in the water. By the mid-1980s, the
discharges had been reduced by 54 and 26% for nitrogen and phosphorus, respectively, resulting in lower chlorophyll a concentrations in
the water (Molvrer and Knutzen 1987).
6.6 Iceland
The composition of macroalgal communities along the Icelandic coasts
have been described by Munda in several papers, and she has emphasized the differences along the coasts, where several Atlantic species
disappear and are replaced by arctic and subarctic species depending on
the influence of different water masses as well as climate (e.g. Munda
1992 and references therein). However, there are few published studies
referring to effects of nutrients on macroalgae along the Icelandic coasts.
Gunnarsson and P6risson (1976) described the impact of sewage discharge on the cover and distribution of littoral algae near Reykjavik.
They found fewer species and less coverage close to the outlet with
reduction of species such as Pelvetia canaliculata, Ascophyllum
nodosum, Vertebrata (=Polysiphonia) lanosa, Sphacelaria radicans and
Elachista fucicola. On the other hand, species of Ulothrix and Prasiola
were found exclusively near the discharge, and moreover, Fucus distichus
grew only near that area.
The risk of eutrophication from discharges, including aquaculture, in
Icelandic coastal waters was pointed out during a symposium on Iceland
1. Wallentinus
to the threshold at about 100 m, and deep water below. High nutrient
concentrations could be measured in the surface layer as far as 10 km
from the discharge, being highest on the northern side of the fjord, and
even 25 km from the discharge there were indications of somewhat
increased nutrient levels. Reduced oxygen levels were measured in the
deep water in late summer.
Molvrer and Knutzen found an almost total dominance of green algal
associations (species of Ulothrix, Enteromorpha and Urospora) in the
littoral zone along 4-5 km on the northern side. Fucoids were absent,
whereas they occurred in the fjord inside the point of discharge. In
addition, the filter-feeding Semibalanus balanoides and Mytilus edulis
were present in large amounts, probably being favoured by high plankton concentrations and partly competing for space with the algae. Nitrogen and phosphorus content in the fucoid tissues were also increased at
stations where the nutrient concentrations were high and showed a linear
correlation with the concentrations in the water. By the mid-1980s, the
discharges had been reduced by 54 and 26% for nitrogen and phosphorus, respectively, resulting in lower chlorophyll a concentrations in
the water (Molvrer and Knutzen 1987).
6.6 Iceland
The composition of macroalgal communities along the Icelandic coasts
have been described by Munda in several papers, and she has emphasized the differences along the coasts, where several Atlantic species
disappear and are replaced by arctic and subarctic species depending on
the influence of different water masses as well as climate (e.g. Munda
1992 and references therein). However, there are few published studies
referring to effects of nutrients on macroalgae along the Icelandic coasts.
Gunnarsson and P6risson (1976) described the impact of sewage discharge on the cover and distribution of littoral algae near Reykjavik.
They found fewer species and less coverage close to the outlet with
reduction of species such as Pelvetia canaliculata, Ascophyllum
nodosum, Vertebrata (=Polysiphonia) lanosa, Sphacelaria radicans and
Elachista fucicola. On the other hand, species of Ulothrix and Prasiola
were found exclusively near the discharge, and moreover, Fucus distichus
grew only near that area.
The risk of eutrophication from discharges, including aquaculture, in
Icelandic coastal waters was pointed out during a symposium on Iceland