Tor Eiliv Lein

Spore dispersal in Laminaria hyperborea (Laminariales, Phaeophyceae)

Abstract Large areas of barren sea floor are found in northern Norway. These are limited to the inner coast: the outer coast is undisturbed with an intact kelp forest where the dominant species is Laminaria hyperborea. The kelp forest is an important spore source for the reforestation of barren areas, and its dispersal range is of vital importance. Experiment using sampling devices at varying distances from the kelp forest have shown the dispersal range of a populaiion of L. hyperborea plants to be at least 200 m. Large numbers of zoospores were found in samples taken from the water column at a depth of 5 m both within and 50 and 200 m from the kelp forest. Laboratory experiments have shown that spores probably swim as long as they can and thereafter sink passively out of the water column to settle.

Population studies of Laminaria hyperborea from its northern range of distribution in Norway

Eight populations of Laminaria hyperborea from wave-exposed localities in Finnmark (70–71°N) were compared with two populations in Vega (65 °N). Standing stock in shallow water (3–5 m) was within the same range in the two areas (6–16 kg fr. wt. m-2). Both the highest and lowest value of standing stock were registered in Finnmark. Degree of wave-exposure was determined by the numbers of sectors exposed to open sea at each locality, with each sector given a relative wind force value. The most wave-exposed locality in Vega had a slightly higher annual biomass production as a function of plant age compared with the populations from Finnmark within a similar range of wave exposure. Of the two localities in Vega the most wave-exposed one had a higher annual biomass production per plant than the more sheltered one. The most wave-exposed locality examined was situated in Finnmark and exhibited the lowest annual biomass production per plant. Recruits (one-year-old plants) were found at all the localities except at one locality in Finnmark. The plants reached a higher age in Finnmark (13–18 years) than in Vega (8–9 years).

The newly introduced species Heterosiphonia japonica Yendo (Dasyaceae, Rhodophyta): geographical distribution and abundance at the Norwegian southwest coast

The newly introduced red alga Heterosiphonia japonica, previously denoted as Dasysiphonia sp., has, since its first record in Europe in 1994, established populations in the Netherlands, Spain, France and Norway. In order to investigate the geographical distribution of the species along the Norwegian southwest coast, 83 localities were dredged along a total distance of 830 km, and the abundance of H. japonica recorded on a semi‐quantitative scale in 2000–2001. H. japonica was present in the entire range investigated. The local abundance of H. japonica at 40 localities in an area south of Bergen was recorded by dredging. H. japonica was not present at wave‐exposed localities, but was abundant at the more sheltered localities where it could constitute up to 65% of the total algal content of the dredge. The size distribution in a population was also studied at one locality during 1 year. Plants in good condition were found throughout the year and a large number of plantlets were present during all seasons. The results of this study suggest that the species has a high dispersal and recruitment capacity. The effect of H. japonica on indigenous ecosystems has yet to be determined.

The effects of Littorina littorea L. (Gastropoda) grazing on littoral green algae in the inner Oslofjord, Norway

Abstract Quantitative studies of Littorina littorea and mainly Enteromorpha compressa (L.) Grev. and Blidingia minima (Naq. ex. Klutz) Kylin in the polluted parts of the fjord have shown that the abundant green algal vegetation found in 1973, in 1976 and 1978 was reduced or absent from most of the localities with dense snail populations. Analysis of the density of Littorina and the occurrence of Enteromorpha (including Blidingia) indicated a negative correlation between the algea and the herbivorous snails (correlation coefficient: - 0.82). Transplantation and exclusion experiments with Littorina in the field showed that snail grazing during summer had a clear and recognizable negative effect on the occurrence and reestablishment of the algae. The snails often formed fronts which grazed the algae and generally left behind a greatly reduced algal vegetation consisting mainly of larger Fucus individuals and encrusting algae. The results indicated that snail grazing in the investigated area must have been an...

Prymnesium parvum Carter (Prymnesiophyceae) in association with macro algae in Ryfylke, southwestern Norway

Abstract During summer 1989, a bloom of P. parvum led to loss of approximately 750 tonnes of salmon and rainbow trout in fish farms in Ryfylke. The flagellate was observed densely covering fish nets and various littoral macroalgae in the fjord. Preliminary experiments in laboratory showed that P. parvum grown in nutrient-poor water swam towards Cladophora sp. These observations may indicate heterotrophic use of dissolved organic matter from the macroalgae or from epiphytic diatoms associated with the macroalgae.

Changes of macroalgal biodiversity in sublittoral sites in southwest Norway: impact of an introduced species or higher temperature?

Abstract The Pacific red alga Heterosiphonia japonica has dispersed rapidly along European shores. Due to the species’ high abundance in many habitats, an impact on species richness and composition of local macroalgal communities might be expected. Higher sea temperatures may also influence local macroalgal composition, by providing more favourable conditions for species requiring higher temperatures. Macroalgal composition at 22 sublittoral sites along the south-western coast of Norway investigated prior to the establishment of H. japonica (1994–1995) were reinvestigated in 2003–2004, using similar methods. The total number of species collected in the area was approximately the same in the present investigation as in the previous study. With regard to number and composition of species at each site, there were no significant differences between sites with high abundance of H. japonica and sites with low or no abundance. Similarity percentage analysis (SIMPER) showed that there were temporal changes in composition of the macroalgal communities, mainly caused by higher frequency of ‘southern species’ (species with a northern limit on our coast). There was a significant increase in the percentage share of such species in the reinvestigations. The temporal differences observed are most likely caused by several warm summers/autumns and mild winters since the first investigation, which may favour a higher abundance of ‘southern species’. Heterosiphonia japonica was the most important species contributing to temporal dissimilarity in the area. This paper concludes that H. japonica has caused no negative impact on regional algal species richness in the relatively short time span since its introduction.

Mass-occurrence of a brown filamentous endophyte in the lamina of the kelp Laminaria hyperborea (Gunnerus) foslie along the southwestern coast of Norway

Abstract The mass-occurrence of spot disease on the dominant kelp species (Laminaria hyperborea (Gunnerus) Foslie) in Norway is described. The spots were associated with an endophyte provisionally assigned to the genus Streblonema and growing mainly in the mucilage canals in the outer cortex of the lamina. Spot disease had a mean cover on old plants (< 4 years) of 2.3–16.7 % of the lamina on two stations and was found on more than 20 % of the plants on all stations examined. After a period of strong wind, heavily infested plants had major lamina loss, and many kelp plants were observed without lamina. Sori were not normally found on infested parts of the lamina. There was no correlation between infested areas of the old lamina and the formation of the new lamina in early winter.

A newly immigrated red alga (‘Dasysiphonia’, Dasyaceae, Rhodophyta) to the Norwegian coast

Abstract A red alga, (‘Dasysiphonia’, Dasyaceae, Rhodophyta), was recorded for the first time in Norway in 1996. The species is identical to an alga, first observed in Europe from the coast of the Netherlands in 1994, probably introduced from the North Pacific. A brief description and the seasonal development of the Norwegian plants are given. In 1997–99 it was found on 15 new sites in the Hordaland and Sogn og Fjordane counties. It is assumed that the species spread fast, and in a few years will be a common alga on a larger part of the Norwegian coast.

Environmental effects of a herring mass mortality in northern Norway. Impact on and recovery of rockyshore and soft-bottom biotas

Abstract In October 1984 a school of herring died in the small shallow bay of Alterosen, Lofoten, northern Norway. During the decay of the fish, subtidal sediments turned black from sulphides while fats and oils floated ashore covering seaweeds and rocks. In the subtidal the soft-bottom macrofauna was killed. Recovery took more than three years, following typical successional patterns. The polychaetes Capitella capitata and Scolelepis fuliginosa had high abundances during 1985 and 1986. Intertidal damage was limited. In the rocky shore the key algal species, Ascophyllum nodosum, tolerated the pollution, but encrusting algae and sponges, and epiphytes were locally affected. Intertidal sediment fauna was only affected during autumn 1984. The different impact and recovery of the intertidal and subtidal communities was found to be in marked contrast to other cases of long-term organic pollution. The results are discussed in view of various effects of stress and disturbance on communities.

A method for the experimental exclusion of Littorina littorea L. (Gastropoda) and the establishment of fucoid germlings in the field

Abstract A new method for the exclusion of Littorina littorea L. and methods for the establishment and growing of fucoids on experimental granite plates and on the rocky shore are described. The equipment used requires regular attention, but provides more natural conditions of light, wave exposure, and recruitment of flora and fauna, compared with the use of wire cages. The grazing activity of Littorina littorea was highest from April to September, and significantly less during October–March in the inner Oslofjord, Norway.