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Sediment cores were collected from an area off the west coast of Norway, where a well-established kelp community made up mainly of Laminaria hyperborea is found. Chemical analyses of the sectioned sediment cores were made, which included organic carbon, carbohydrates and phenols. These were used to collate the sediments in order to establish whether the different sites had a common origin and if this was kelp-related. The organic matter content in the surface sediments appears to be related to the water depth, which determines the degree of perturbation at the sediment-water boundary and hence the sedimentation of the organic matter. The relation between carbohydrates and phenols in the sediment appears to indicate a common origin. However, the carbohydrate and phenol content in the sediment organic fraction appears to closely resemble (to be analogous) to that of the kelp Laminaria hyperborea. Although there are some diagenetic and decomposition changes in the subsurface (historical) organic matt...

During the growing season from February to May, a release of stored nitrate into the seawater medium was observed in a night and day incubation of 2–3-year-old plants of Laminaria hyperborea. A large part of the nitrate that was released appears to be assimilated by photosynthesis during the day. This is at variance with the common consensus that stored nitrate in kelp is translocated to the growing tissues at the meristem. During the non-growth season, however, there was active uptake of nitrate during both day and night irrespective of the nitrate level in the seawater medium. The uptake rate (nmole g−1 h−1) was found to depend on the initial nitrate level.

To investigate the importance of benthic vegetation for shallow infaunal assemblages, macroinvertebrates were sampled inZostera marina meadows and in adjacent bare sand at three sites in the Skagerrak region and one in the Western part of Norway. A total of 3777 individuals were encountered, representing mainly the faunal groups Annelida, Nemertea, Echinodermata, Crustacea and Mollusca. Twice as many individuals were found in theZ. marina meadows compared to the bare sand. Oligochaetes were the most abundant group (29% of total number of individuals), followed by crustaceans (24%), polychaetes (18.5%) and molluscs (16%). Polychaetes showed the highest species number (42), followed by molluscs (30) and crustaceans (26). Multivariate cluster technique showed the highest similarities within sites and thereafter grouping according to the two different habitats;Zostera and sand. No regional differences were evident between the Skagerrak sites and the site in Western Norway, as the site from Western No...

The importance of the tissue C : N ratio and the content of phlorotannins for the suitability of kelp, Laminaria hyperborea, as food for consumers was tested. Laminas from kelp were sampled in winter. In the laboratory, the kelp was experimentally degraded for 3, 14 and 44 days by kelp-associated bacterial communities under aerobic conditions. The kelp C : N ratio and phlorotannin contents decreased with degradation. The kelp was fed to the kelp-associated amphipods Ampithoe rubricata and Gammarus locusta in no-choice feeding experiments. The growth of amphipods was higher on kelp that was not degraded or degraded for short periods than on kelp degraded for long periods. The results show that the content of phlorotannins in L. hyperborea lamina is of little importance for their suitability as food. An earlier study using kelp with a high C : N ratio showed increased amphipod growth after long degradation and the results from both studies suggest that the C : N ratio of kelp varies greatly with se...

The macrophytes Fucus serratus and Zostera marina form similar substrates for associated flora and fauna in shallow waters in Norway. While F. serratus forms a more or less continuous belt on rocky substrate along the coast, Z. marina forms disjunct populations on sandy or muddy bottoms. This study focused on the organisms associated with these two macrophytes in two localities in the Skagerrak region. In total, 130 taxa of epiphytic organisms were identified: 22 green algae, 41 red algae, 32 brown algae, eight diatoms and 27 sessile animals. One hundred and twenty-seven taxa of mobile macrofauna were registered. The dominant group was crustaceans, with amphipods as the order containing most species. Many species of both plants and animals preferred one or the other habitat. It is concluded that coastal macrophyte systems have high species diversity.

The invasive brown alga Sargassum muticum was first observed growing attached in Norway in 1988. Since then, the species has spread rapidly and is now an established member of the algal community in sheltered areas along the entire Skagerrak coast. In 1999, one population in the outer Oslofjord was investigated for epiphytic macroalgae, and evidence was found of a rich macroalgal community on S. muticum. A total of 82 different algal taxa were identified: 34 rhodophytes, 23 phaeophytes and 25 chlorophytes. The epiphytes found on S. muticum included more than 25% of the total number of algal species found in the Oslofjord area. A summary of all species recorded is given, with floristic notes on particular taxa.

Annual growth per plant and allocation of growth to the stipe were measured in 2- to 4-year-old plants of Laminaria hyperborea from five stations with different degrees of wave exposure and different amounts of canopy biomass. Low growth in plants with initial stipe lengths of less than about 40 cm suggested that the presence of canopy-forming plants suppresses growth of understorey plants, and this was supported by the high lamina growth rate of understorey plants after removal of the canopy-forming plants. Canopy biomass and wave exposure were found to exert a differential effect on the growth of the age groups examined. Average annual growth per plant in 2- to 3- year-old plants decreased with increasing canopy biomass; growth of 4 year-old plants was not significantly influenced by canopy biomass, but increased with increasing wave exposure of the sites, suggesting an influence of some factor connected with wave exposure. The allocation of annual growth to stipe and lamina was also found to be influen...

The seasonal growth pattern of canopy plants has been compared with that of first-year plants. Large, canopy-forming sporophytes grew between January and June. The seasonal variation in total carbon content of the lamina reflected the seasonal pattern of storage carbohydrates, with high content in the summer and autumn, and decreasing content after growth started in January. Vegetative and reproductive laminae contained similar percentages of carbon in dry weight in January, indicating that the process of sorus formation did not involve high consumption of stored carbohydrates in reproductive plants. The nitrogen content of the laminae of canopy plants was high during the growth period and low during the rest of the year. The high nitrogen content during spring may reflect storage in a period of excess ambient nitrate. The first-year plants grew until the end of September, with the highest relative growth rate during July. During the summer the nitrogen dry weight content of the first-year plants...

Lithophyllum crouanii and Titanoderma pustulatum have been found to be common epiphytes on Laminaria hyperborea stipes from western Norway. The two species were studied by light microscopy and SEM. The main character used to separate the two species macroscopically is that L. crouanii has immersed conceptacles seen as white circles on the thallus surface, whereas T. pustulatum has gradually raised conceptacies. Sporangial conceptacies are uniporate in both species. L. crouanii has zonately divided tetrasporangia and gametophytic plants were common. Only bisporangial plants were found in T. pustulatum. In vegetative specimens a cross section revealed that T. pustulatum has a unistratose hypothallium composed of oblique palisade cells and a bistratose margin. L. crouanii has horizontally aligned perithallial cells of more or less equal size and never has a bistratose margin.

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.

G. latifolium from the Norwegian west coast was isolated into unialgal culture and growth responses to various regimes of temperature, light, and salinity were determined. The morphological variability in cultures of cloned material and of field-collected specimens is discussed in relation to species delineation. Comparisons with cultured strains referable to G. pusillum from Norway, France, and Ireland were undertaken. Enzyme electrophoresis provided supporting data for the distinction between the two entities from Norway. The distribution of G. latifolium along the Norwegian coast was recorded from examination of available herbarium specimens. The boundary near the entrance to the Skagerrak coast corresponds to lethal winter temperatures (< 0° C), while the northern boundary corresponds to a summer growth limit near the 10° C August isotherm, below which little or no growth occurs.