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The invasive brown alga Sargassum muticum was first recorded in Norway in 1988 and is presently common in the sublittoral fringe on the sheltered coast in South Norway. Here, results from a study on mesofauna associated with S. muticum in an archipelago on the southwest coast of Norway are presented, with two stations placed in sounds exposed to tidal currents and two in sheltered bays. Sargassum muticum occurred with a patchy distribution and an estimated density of less than 7 individuals m−2 at three of the stations (two in sheltered bays and one in a sound) and 42 individuals m−2 at the fourth station (placed in a sound). A total of 102 distinct faunal taxa were identified, with an average of 31 taxa per sample. Crustacea and Gastropoda constituted around half of the identified taxa. Fauna richness showed no relation to site type but had a curvilinear correlation with habitat size (dry weight of thallus). Total and sessile fauna richness showed a significant negative correlation with branching density. Vagile faunal density showed a curvilinear correlation with weight of epiphytes and was significantly related to site type with higher densities in the bays. The community composition of vagile fauna reflected this and was significantly related to site type, but not to epiphyte weight or branching density. When including sessile taxa in a community analysis the stations became less separated, and the community was significantly influenced by branch density. Thus, both site characteristics and morphology of S. muticum influenced the associated fauna community. publishedVersion

Vertebrata lanosa is a small red epiphytic alga growing almost exclusively on Ascophyllum nodosum. It has recently gained attention as a food alga in the North Atlantic. We examined distribution of V. lanosa in relation to environmental factors, by measuring cover of A. nodosum and V. lanosa in sample quadrats at 27 stations in an area in southwestern Norway. The probability of finding high cover (hotspots) of V. lanosa (defined as scores of V. lanosa belonging to the upper 25 % of data) was analysed in relation to height above Chart Datum, wave exposure, cardinal direction, inclination and substratum type. The relationship between amount (cover or volume) of the host alga (A. nodosum) and cover of V. lanosa was also examined. A significant and positive relationship between high cover of V. lanosa and increasing wave exposure was found, which may be attributed to the fact that wave action can cause scrapes and wounds on A. nodosum branches, where spores of V. lanosa have higher chances of successful settlement and survival. The results also showed a significant negative impact of high cover or large volume of A. nodosum on V. lanosa. Finally, the probability of finding high cover of V. lanosa was highest in the middle part of the Ascophyllum zone. The results suggest that the epiphyte and its main host do not have completely overlapping habitat requirements, and that sheltered areas with high biomass of A. nodosum are likely to contain relatively little V. lanosa for harvesting.

The health of the world's oceans is intrinsically linked to the biodiversity of the ecosystems they sustain. The importance of protecting and maintaining ocean biodiversity has been affirmed through the setting of the UN Sustainable Development Goal 14 to conserve and sustainably use the ocean for society's continuing needs. The decade beginning 2021-2030 has additionally been declared as the UN Decade of Ocean Science for Sustainable Development. This program aims to maximize the benefits of ocean science to the management, conservation, and sustainable development of the marine environment by facilitating communication and cooperation at the science-policy interface. A central principle of the program is the conservation of species and ecosystem components of biodiversity. However, a significant omission from the draft version of the Decade of Ocean Science Implementation Plan is the acknowledgment of the importance of monitoring and maintaining genetic biodiversity within species. In this paper, we emphasize the importance of genetic diversity to adaptive capacity, evolutionary potential, community function, and resilience within populations, as well as highlighting some of the major threats to genetic diversity in the marine environment from direct human impacts and the effects of global climate change. We then highlight the significance of ocean genetic diversity to a diverse range of socioeconomic factors in the marine environment, including marine industries, welfare and leisure pursuits, coastal communities, and wider society. Genetic biodiversity in the ocean, and its monitoring and maintenance, is then discussed with respect to its integral role in the successful realization of the 2030 vision for the Decade of Ocean Science. Finally, we suggest how ocean genetic diversity might be better integrated into biodiversity management practices through the continued interaction between environmental managers and scientists, as well as through key leverage points in industry requirements for Blue Capital financing and social responsibility. info:eu-repo/semantics/publishedVersion

The flavonoid content in leaves of Zostera marina and the endangered Zostera noltii, including mono- and disulphated flavonoids, from different sample localities were characterized. Seasonal variation of both individual and total flavonoid, as well as rosmarinic acid concentration were revealed. Minor amounts of luteolin 7-(6″-malonyl)glucoside ( 6 ) and apigenin7-(6″-malonyl)glucoside ( 11 ) were identified in Z. noltii for the first time. The total flavonoid content was found to be higher in Z. noltii than in Z. marina at most of the examined localities, and the qualitative flavonoid content was somewhat different in the two species. The quantitative variation of flavonoids and rosmarinic acid was found to be relatively consistent from year to year in Z. marina during a period of three years. The two species appeared though to have a different flavonoid production in the various seasons at the West coast. While Z. marina had the highest content in young leaves in May or June, with a markedly decrease from June to September and the lowest measured content in February, Z. noltii had the lowest measured flavonoid content in May/June followed by an increase from June to September and the highest measured content during wintertime in February. The observed seasonal differences may be related to the fact that Z. noltii is considered a perennial, thermophilous species, and the increasing flavonoid production during the colder seasons from September to March/April in Norway may serve as a protective function.

Kelps and fucoids are important members of temperate seaweed communities, but may be negatively impacted by climate change and non-native species. We used a field experiment to investigate the effect of higher temperatures and a non-native seaweed, Sargassum muticum, on the kelp Saccharina latissima and fucoid Fucus serratus. All 3 are canopy-forming species which may grow together in the infralittoral and upper sublittoral zones in southwestern Norway. Artificial assemblages with different combinations of the species were placed in the shallow sublittoral, and length changes, weight changes and survival of the thalli were measured. This was done during a hot summer and again during a cool summer. The results showed that the species and their competitive interactions were affected by the different thermal conditions. S. latissima was the most successful species in the cool summer and had an impact on the other 2 species, but it was strongly negatively affected by the hot summer. Under these conditions, F. serratus became the most successful species, gaining the most weight. The effect of Sargassum muticum on the native species was no larger than the effect of intraspecific competition within those species. At the end of both summers S. muticum was in poor condition, potentially caused by low seawater nutrients resulting in low internal nitrogen. publishedVersion

This is a post-peer-review, pre-copyedit version of an article published in Biological Invasions. The final authenticated version is available online at: https://doi.org/10.1007/s10530-019-02058-x. We present the results of an inventory and status assessment of alien species in Norway. The inventory covered all known multicellular neobiota, 2496 in total, 1039 of which were classified as naturalised. The latter constitute c. 3% of all species known to be stably reproducing in Norway. These figures are higher than expected from Norway’s latitude, which may be due a combination of climatic and historical factors, as well as sampling effort. Most of the naturalised neobiota were plants (71%),followed by animals (21%) and fungi (8%). The main habitat types colonised were open lowlands (79%), urban environments (52%) and woodlands (42%). The main areas of origin were Europe (67%), North America (15%) and Asia (13%). For most taxa, the rate of novel introductions seems to have been increasing during recent decades. Within Norway, the number of alien species recorded per county was negatively correlated with latitude and positively correlated with human population density. In the high-Arctic territories under Norwegian sovereignty, i.e. Svalbard and Jan Mayen, 104 alien species were recorded, of which 5 were naturalised.

Safeguarding the services provided by marine forests inherently depends on an accurate understanding of macroalgal species diversity. Here, we provide the first DNA barcode survey of marine macroalgae from Norway, with a focus on the Bergen area, and compared our findings to morphological listings for the corresponding location. Specimens were sampled 14–20 April and 3–13 June 2016, and variously sequenced for several genetic markers, including the five prime end of the cytochrome c oxidase subunit I gene (COI-5P), elongation factor tufA, and the ribulose-1, 5-biphosphate carboxylase large subunit gene (rbcL). We generated 655 new barcode records for COI-5P, 11 for tufA, and 50 for rbcL, representing nine species of Chlorophyta, 51 species of Phaeophyceae, and 74 species of Rhodophyta. Sequence data confirmed the presence of 113 morphological species. A further 17 genetic groups indicated the presence of new species for the area, only six of which were linked to formally described species. The remaining four genetic records were uncertain in terms of morphological species assignment and relation to the local flora. We recommend further DNA barcoding surveys in the area, as only a third of the listed morphological species were genetically confirmed.

The introduction of a non-native, habitat-forming macroalga may have impacts on the seaweed-associated faunal community. Codium fragile subsp. fragile is a well-known and widespread algal invader that may compete with native habitat-forming macroalgae and affect ecosystem services. This alga can be abundant at semi-exposed/sheltered sites on the south-west coast of Norway, where its vertical distribution range overlaps with another canopy-forming alga, the native Fucus serratus. Whether these seaweeds support similar or dissimilar associated communities will influence the ecological impact of C. fragile subsp. fragile. Therefore, the richness and composition of fauna associated with these species was assessed by sampling at three localities. While the majority of taxa occurred on both F. serratus and C. fragile subsp. fragile, there were clear differences in community composition between them. Fauna taxa richness and community composition were also related to macroalgal epiphyte abundance, and there were a number of taxa associated to high epiphyte samples. The results suggest that shared macroalgal epiphytes lead to higher similarity between the invertebrate communities associated with C. fragile subsp. fragile and F. serratus, providing correlative evidence that epiphytic macroalgae play a role in shaping the impact of this macroalga on associated fauna.

Codium fragile subsp. fragile (hereafter C. fragile) is a widespread non-native chlorophyte. Experimental and observational approaches were used to examine the influence of temperature on its growth and local distribution in southwestern Norway, where it has been established for over 80 years. Growth was measured in laboratory experiments at current and predicted seasonal minimum and maximum seawater temperatures, and under natural conditions by recording length over 1 year in the field. The results indicated that if temperatures increase, C. fragile growth rate may increase in spring, but not in mid-autumn/winter due to low light. Thallus fragmentation was common in autumn/winter in the field, but very rare in the winter-temperature laboratory experiment, indicating that low temperature is not the only driver. Growth occurred at temperatures which are reported as too low for growth in other locations, suggesting that C. fragile can acclimatise/adapt to local temperature regimes. Local distribution was examined by surveying abundance using categories based on the number of thalli and their arrangement (scattered/patch/zone) at 46 stations from 2011 to 2016. Codium fragile colonised the stations relatively often, but was frequently lost from sites with only bedrock compared to sites with stony substratum present (cobbles/boulders). It was more likely to be consistently present at sites with stones and could form dominant patches of canopy in the upper sublittoral on this substratum. An increase in the number of stations with C. fragile present was seen after two mild winters, suggesting that higher minimum temperatures may increase site occupancy of C. fragile in this region. acceptedVersion

Genetic affiliation, nuclear DNA content, and gamete functioning were examined in small salt marsh Fucus from three localities in western Ireland. Individuals with small and dioecious receptacles were found at all localities, but production of germlings was only evident from those at Locality 1. Here, the Fucus vegetation formed a morphological cline from F. vesiculosus with bladders in the mid intertidal to small Fucus individuals lacking bladders in the salt marsh of the upper intertidal. Measurements of nuclear DNA content ranged from 1 1.8 pg at this locality, with the F. vesiculosus individuals in the lower range. At the two other localities, the small salt marsh Fucus formed distinct morphological entities. Microsatellite analyses revealed that the small salt marsh Fucus individuals from Locality 2 were derived mainly from F. vesiculosus, whereas those from Locality 3 were hybrids between F. vesiculosus and F. spiralis with greatest affiliation to F. spiralis. While the small salt marsh Fucus forms from Locality 2 had high nuclear DNA content (ca. 4 pg) and were probably octoploids, the small salt marsh ucus from Locality 3 formed two groups: one with high (3.9 4.6 pg) and one with low (1.5 1.9 pg) nuclear DNA content. Nuclear DNA content measured in individuals from Locality 3 varied between 1.1 2.8 pg in F. vesiculosus and 2 3.5 pg in F. spiralis and showed a more or less stepwise increase in both species, consistent with polyploidy. We hypothesize that the small salt marsh Fucus forms originate from genome size changes in the parental taxa. The final version of this research has been published in European Journal of Phycology. © 2017 Taylor & Francis

The distribution of Codium fragile subsp. fragile and the native canopy-forming alga Fucus serratus was recorded at 51 sites in a 20 km long, sheltered region on the southwest coast of Norway. The purpose of the study was to examine if these species are potentially competing and how their distributions are related to wave-exposure and substrate. Codium fragile subsp. fragile was patchily distributed, a pattern which appears to have been sustained over time since its introduction to this area. It was almost always observed growing below mean low water, in the low intertidal and shallow subtidal. Both substrate type and wave-exposure influenced the vertical distribution of C. fragile subsp. fragile; growth occurred higher on the shore at sheltered sites and deeper in the subtidal on stony substrate. Its vertical range of growth overlapped with that of F. serratus and, when C. fragile subsp. fragile was abundant, F. serratus tended to grow higher on the shore and at lower abundances. This suggests that C. fragile subsp. fragile is affecting F. serratus in this area through competition, but only in the lower portion of the fucoid’s vertical range and only at sites favorable for its own growth with regard to shelter and substrate.

Concentration of 99Tc has been measured in fucoids and molluscs, sampled in a sheltered intertidal at the southwest coast of Norway from February to November 2006. The concentrations of 99Tc in molluscs differed significantly between species. The filtering bivalve Mytilus edulis had the lowest concentrations with averages of 2.3–5.9 Bq kg−1 d.w., while the herbivorous gastropods Littorina littorina, Littorina obtusata and Patella vulgata had higher concentrations. P. vulgata and L. obtusata had the highest concentrations, 40–47 and 26–30 Bq kg−1 d.w., respectively. L. obtusata has a specialized habit of living, and prefers to feed on fucoids. P. vulgata can graze extensively on the fucoid Ascophyllum nodosum when available. Fucoids are known to have very high uptake of 99Tc, and this was also found in the present study. The high 99Tc-concentrations of L. obtusata and P. vulgata are most likely due to their habit of feeding on fucoids.

The present study showed a differential composition of amphipod fauna on red algae with different morphology. The stipes of Laminaria hyperborea are covered with epiphytes, of which red algae constitute a main group. A rich invertebrate fauna dominated by gastropods and amphipods is associated with the epiphytes. The algae may function as a habitat providing refuge against wave action and predation, or as food. The study was carried out on the southwest coast of Norway. Common epiphytic red algae of different morphology with associated amphipods were sampled at three different depths at three localities with kelp forest (L. hyperborea). Although the total amphipod densities increased with habitat size, the distribution of amphipods on the selected epiphytes differed. Ptilota gunneri is repeatedly feather-branched with a complex branching pattern and has high densities of small amphipods, dominated by Jassa falcata and species from the familiy Stenothoidae. The filamentous epiphyte Polysiphonia el...

The surfaces of kelp are covered with bacteria that may utilize kelp-produced carbon and thereby contribute significantly to the carbon flux in kelp forest ecosystems. There is scant knowledge about the identity of these bacteria and about which kelp-derived carbon sources they utilize. An enrichment approach, using kelp constituent carbon sources for bacterial cultivation, was used to identify bacterial populations associated with the kelp Laminaria hyperborea that degrade kelp components. In order to assess whether the cultured bacteria are significant under natural conditions, partial 16 rRNA gene sequences from the cultured bacteria were compared to sequences obtained from the indigenous bacterial communities inhabiting natural kelp surface biofilms. The results identify different members of the Roseobacter clade of Alphaproteobacteria in addition to members of Gammaproteobacteria that are involved in kelp constituent degradation. These bacteria are observed sporadically on natural kelp surfaces and may represent opportunistic bacteria important in degradation of dead kelp material. Many of the cultured bacteria appear to be generalists that are able to utilize different kelp carbon sources. This study is the first to link culturable kelpassociated bacteria with their occurrence and possible roles in the natural environment. publishedVersion

The distribution of technetium-99 ( 99 Tc) in annual growth segments of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) from the southwestern coast of Norway is examined in samples collected from January to November 2006. A twenty-fold increase in the 99 Tc-concentration from the youngest to the oldest growth segments was found. The concentrations ranged from 42 to 98 Bq/kg dry weight (d.w.) and from 964 to 1000 Bq/kg d.w. in growth segments formed in 2006 and 1996, respectively. In addition, a seasonal variation in the 99 Tc concentration was observed in the actively growing 2006-segments: concentrations decreased from 98 Bq/kg d.w. in April to 54 Bq/kg d.w. in June; there was a further reduction from June to August (42 Bq/kg d.w.); and, finally there was an increase from August to November (93 Bq/kg d.w.). In most of the segments formed between 2000 and 2005, there was a tendency of slightly decreasing 99 Tc-concentrations between June and November but this pattern was not observed for the older growth segments. In order to find an explanation for the non-homogenous distribution of 99 Tc within thalli of A. nodosum , different hypotheses are discussed. Uptake and elimination of 99 Tc appears to be most pronounced in the actively growing segments. To date, such non-homogenous distribution of 99 Tc within thalli of A. nodosum has not been taken into consideration, neither in connection with sample collection nor analysis. This paper shows that special protocols must be followed if A. nodosum is going to be used as a bioindicator for 99 Tc in the marine environment. A sampling strategy is proposed.

Coastal kelp forest ecosystems provide important habitats for a diverse assemblage of invertebrates, fish and marine top-predators such as seabirds and sea mammals. Although kelp is harvested industrially on a worldwide scale little is known about the multi-trophic consequences of this habitat removal. We investigated how kelp fisheries, which remove feeding and nursery grounds of coastal fish, influence local food webs and the availability of food to a marine top predator, the great cormorant (Phalacrocorax carbo). We conducted experimental harvesting of the canopy-forming kelp (Laminaria hyperborea) during a 3 year period (2001–2003) in an area at the coast of Central Norway while synoptically monitoring fish occurrence and cormorant foraging parameters. Our results demonstrate that cormorants preferentially foraged within kelp-forested areas and performed significantly more dives when feeding in harvested versus un-harvested areas suggesting lower foraging yield in the former case. In kelp areas that were newly harvested the number of small (

Seasonal variations of the cell density and bacterial community composition in biofilms growing on the surface of the kelp Laminaria hyperborea from 2 sites on the southwestern coast of Norway were investigated using total cell enumeration and denaturing gradient gel electrophoresis (DGGE) fingerprinting. The major taxonomical groups of bacteria inhabiting the biofilms were identified by DGGE band sequence classification. The microbial cell density of the biofilm appeared to be highly affected by the seasonal growth cycle of the kelp and was found to be lowest on growing kelp in March (minimum 8.3 × 102 cells cm–2), while on non-growing kelp in July to February, it was around 1.0 × 107 cells cm–2 with large fluctuations. The composition of the bacterial community of the biofilm followed a continuous seasonal succession that may be explained by the influence of both biotic factors such as seasonal changes in the kelp substrate and abiotic factors such as seawater temperature. Planctomycetes and Alphaproteobacteria were frequently detected throughout the year, while Verrucomicrobia, Cyanobacteria, Gammaproteobacteria, Betaproteobacteria, and Bacteroidetes were more sporadically detected. The bacterial communities of the biofilm on kelp showed little overlap with that of the surrounding seawater publishedVersion

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 com...

In order to trace the introduction history of the western Pacific species Heterosiphonia japonica to and within Europe, information on distribution pattern of the species in Europe, oyster import and shipping activity has been compiled and analyzed. Additionally survival of fragments of H. japonica during a simulated journey in ballast water from Asia (Korea) to Europe (France) has been observed. The species was first recorded in Europe near an oyster culture area in Brittany (France) in 1984. Since then, it has spread quickly in Europe. The first introduction into Europe and secondary dispersal in southern Europe has most likely been trough movement of the Pacific oyster Crassostrea gigas. However, survival of H. japonica in temperatures varying from 14 to 28 degrees during a simulated 28-days journey in ballast water was demonstrated, and an introduction by ships from the Pacific Ocean may thus be considered as possible. Spreading of the species in the North Sea area and Scandinavia is most likely due to transport by ships, e.g. as attached to ships hulls, as fragments in ballast water or entangled e.g. in fishing gear.

The red alga Antithamnion nipponicum was discovered on the west coast of Norway, south of Bergen in 2007. From its native range in Japan and Korea the alga was first introduced to the Mediterranean Sea in 1988. Except for a possible report from the Azores (as A. pectinatum) there are no published records from European Atlantic coasts. The introduction to Norway most likely occurred via fouling on ship hulls, or by ballast water. Vegetative and tetrasporangium-bearing plants were found, and the specimens conform to the detailed description recently published by Cho et al. (2005), based on material from Pacific and Atlantic coasts of North America where the alga is also a recent introduction.

Sargassum muticum (Yendo) Fensholt was introduced to European coasts during the 1970s. We studied survival and growth of seeded S. muticum germlings in field experiments on the southwestern coast of Norway, close to its present northernmost limit of distribution in Europe. A cage experiment was conducted twice (using different starting densities of germlings) at 2 localities during the summer and autumn of 2002, each experiment lasting 1 mo. Germling survival was significantly higher within grazer-excluding cages than on unprotected substrate. Germlings within cage controls (cages accessible to mesograzers) experienced intermediate mortality, which was nevertheless closer to that of unprotected than to cage-protected germlings. At a third locality, survival of unprotected germlings was recorded from September 2000 to February 2001, and only 0.6% of the germlings had survived by February. When relating proportion of mortality to initial density of germlings, we found no tendency of positive density-dependent mortality; on the contrary, on the substrate where grazers had access to the germlings, there was a tendency for high mortality when initial density was low and lower mortality when initial density was high. This suggests a ‘swamping’ effect of high germling densities on grazers. The growth of germlings during autumn and winter was very low compared with earlier reported measurements from Spain, and we suggest that relatively slow growth rates may make the germlings vulnerable to grazing impact. The results indicate that herbivorous grazing on early post-settlement stage germlings may be a limiting factor for the spread of S. muticum in southwestern Norway.

During the last decades, trends of increasing sea water temperatures and precipitation have been observed in the North Atlantic. Increasing sea water temperatures are expected to have strong effects on coastal benthic species. Here, the distributions of macroalgae were correlated to hydrographical indexes determined from measurements at sampling and hydrographical stations along the fjord during 2 investigation periods: 1955-1956 and 2008-2009. The following indexes were used: annual maximum sea temperature, minimum salinity, and salinity stress (calculated as the difference between maximum and minimum salinity). In addition, changes in macroalgal species abundance and distribution range in the fjord were calculated. The hydrographical measurements showed higher summer temperatures and reduced salinity stress due to lower winter salinity during 2008-2009. Results from constrained ordination analyses showed that the highest variation of the macroalgal distributions along the fjord was explained by hydrographical indexes from 5 m depth, and that there were strong response differences between the algal groups. The red algae were most strongly and positively correlated with the maximum temperature gradient, and also negatively correlated with increasing salinity stress. Many red algae species also increased in abundance and their distribution ranges shifted further into the fjord in 2008-2009. The brown algae showed the highest negative correlation with increasing salinity stress, and less change in abundance or range shifts along the fjord. Some brown algae species showed a strong correlation with temperature (positive or negative). These results demonstrate that both temperature and salinity changes will impact cold temperate macroalgal communities. publishedVersion

The aim of this study was to determine the impact of sea urchin grazing (Echinus esculentus) and canopy shading on the recruitment of the kelp Laminaria hyperborea in mid-Norway. A spatially variable distribution of sea urchins was observed, and recruitment processes were studied both after disturbance, caused by kelp harvesting removal of the canopy kelps, and in pristine kelp forests. The combination of sea urchin density and the density of canopy-forming kelps had the strongest influence on the density of small kelps in pristine kelp forest, suggesting that both grazing from sea urchins and shading from the canopy contributed to the mortality of small kelps. High densities of small kelps (>20 m−2) were only found in pristine kelp forest together with ≤6 canopy-forming kelps m−2 or

We compared populations of Laminaria hyperborea from different regions along the Norwegian coast (58–71°N). The aim of the study was to examine possible regional differences in population demography and to relate these to latitudinal gradients in ambient temperature and light. A number of population parameters were examined in understory and canopy kelp individuals. We found latitudinal differences in stipe growth rate and growth pattern, mortality, longevity, recruitment and density. Stipe growth rate was higher for young individuals in mid-Norway than in south and north Norway. Mean stipe length was related to temperature and light, and correlated significantly with indices combining temperature during the growth season and daylength in summer. Mortality decreased and longevity increased with increasing latitude, probably because of a temperature decrease with increasing latitude and a general reduction in metabolic rate. Greater longevity may also cause the observed decrease in recruitment rate with increasing latitude, since there are fewer opportunities for understory individuals to replace dead canopy individuals. The development of particularly large kelp in mid-Norway appears to be explained by high growth rates and not a particularly long life span, as earlier assumed. This has consequences for decisions of the optimal harvesting regime for the species in the region, with regard to yield and maintenance of associated biodiversity.

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. Th...

Laminaria saccharina, L. hyperborea and L. digitata (Laminariales, Phaeophyta) were cultivated at 0°C from embryospores. Slow germination of embryospores and temperature-limited growth of primary cells were found. Laminaria saccharina developed most rapidly and produced oogonia 18-20 days after sporulation, and sporophytes after 23-26 days. No differences were found in the rate of development of the primary cells between L. digitata and L. hyperborea; the first oogonia were observed after 20-34 days in L. hyperborea and after 33 days in L. digitata. Sporophytes were observed after 54-59 days in L. hyperborea, whereas the experiment with L. digitata had to be terminated after 42 days. The relatively rapid development of L. saccharina at 0°C suggests good adaptation of the gametophytic stage to Arctic conditions. The slow growth of L. hyperborea and L. digitata at 0°C suggests that this is close to the lowest temperature allowing vegetative development of primary cells of both species. Laminaria hyperborea produces spores during winter and L. digitata during late summer and autumn, and different seasons of gametophytic establishment may possibly explain why L. digitata extends into the Arctic, whereas L. hyperborea does not.

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 sporophyte formation of Laminaria hyperborea (GUNNERUS) FOSLIE in the sea was studied from January till the end of May at a locality on the west coast of Norway. Three series of gametophytes, which had been cultured in red light to prevent sexual reproduction, were transferred to the sea at depths between 10 and 45 m. After about 30 or 70 days in the sea the frequency of sporophytes in each series was registered. From 14 January to 13 February sporophytes had developed at 10 m. From 14 February to 18 March sporophytes had developed at both 10 and 20 m, while from 20 March to 28 May sporophytes had developed at all examined depths. In the period from 20 March to 28 May sporophytes constituted 82 and 27 % of the examined specimens at 40 and 45 m, respectively. In all the other cases where sporophytes were registered, 100 % of the specimens examined had developed into sporophytes. Based on continuous recordings of photon irradiance (PAR) in air and measurements of blue and integrated irradiance ...

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...

Lamina elongation and content of mannitol, laminaran and nitrate were measured during one year in Laminaria saccharina sensu lato from Iceland. The population contained both solid- and hollow-stiped plants. Growth rate was at its minimum from October to December, and started to increase in mid-winter, slightly earlier at 3 m than at 5 m. The increase in growth rate coincided with a strong reduction in stored carbohydrates and an increase in nitrate content of the laminae, indicating that stored mannitol and laminaran provided extra energy for increased lamina growth and/or for nitrate uptake. The results showed that stored mannitol was utilised before laminaran. The growth rate was at its maximum from April to June, and was reduced from June to July. The ambient nitrate concentration at the locality was low from May to August. The nitrate content of the lamina tissue in relation to dry weight was high during spring but was reduced to low values by July, indicating that nitrate levels limited growth during...

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.

Morphological development of Laminaria hyperborea was examined at localities with different degrees of wave exposure. Biomass data were converted to estimates of annual growth of lamina, stipe and hapteron. Allocation of annual growth to the hapteron constituted a small amount of the total production, but increased with increasing wave exposure. At the most sheltered locality, lamina growth amounted to between 80 and 95% of total growth in all age groups, and lamina to stipe ratios (fresh weight) were about 10. A higher portion of the annual growth was allocated to the stipe at the more wave-exposed localities. This resulted in lamina to stipe ratios of between 1 and 2 in old plants, but within these localities no gradual decrease in lamina to stipe ratio with increasing wave exposure was observed. At some localities a maximum of growth allocation to the stipe was found in the intermediate age groups. This was most pronounced at the locality with the highest density of canopy plants and intermediate wave exposure. Also, at this locallty the stipes were longer in relation to their weight than at the other localities. These results indicate that light environment, in additlon to wave exposure, Inay influence the stipe morphology and the relationship between stipe and lamina growth. At one station stipe growth was also calculated in individual tagged plants using the lengthweight relationship. The results agreed with those obtained by the biomass method. The highest allocation of growth to the stipes was found in 3 and 4 yr old plants. Maximum annual stipe growth (weight increase) occurred in 4 and 5 yr old plants and decreased in older plants, while maximum lamina growth was found in the oldest plants.

Kelp forests worldwide are known as hotspots for macroscopic biodiversity and primary production, yet very little is known about the biodiversity and roles of microorganisms in these ecosystems. Secondary production by heterotrophic bacteria associated to kelp is important in the food web as a link between kelp primary production and kelp forest consumers. The aim of this study was to investigate the relationship between bacterial diversity and two important processes in this ecosystem; bacterial secondary production and primary succession on kelp surfaces. To address this, kelp, Laminaria hyperborea, from southwestern Norway was sampled at different geographical locations and during an annual cycle. Pyrosequencing (454-sequencing) of amplicons of the 16S rRNA gene of bacteria was used to study bacterial diversity. Incorporation of tritiated thymidine was used as a measure of bacterial production. Our data show that bacterial diversity (richness and evenness) increases with the age of the kelp surface, which corresponds to the primary succession of its bacterial communities. Higher evenness of bacterial operational taxonomical units (OTUs) is linked to higher bacterial production. Owing to the dominance of a few abundant OTUs, kelp surface biofilm communities may be characterized as low-diversity habitats. This is the first detailed study of kelp-associated bacterial communities using high-throughput sequencing and it extends current knowledge on microbial community assembly and dynamics on living surfaces.

The effect of weathered, crude oil on Ascophyllum nodosum was tested in an outdoor experiment and in a laboratory experiment. Adult A. nodosum plants which were exposed to oil in an outdoor basin for 3 days showed reduced growth for a certain period of time, after which growth recovered. Also, some necrotic damage was observed. Three-week-old and 1-year-old germlings placed under the adult plants showed no significant reduction in number compared to control plants. In the laboratory experiment some of the 1-month-old germlings were initially exposed to oil for 6 min, some for 1 h, some for 3 h and some for 5 h. After 3 weeks in running, filtered water oil-exposed germlings had reached the same length as those in the control groups, and no effect of exposing the germlings to oil for different lengths of time at the start of the experiment was found. The results indicate that a limited oil pollution of weathered, crude oil may reduce growth and biomass of adult plants for a certain period of time. However, this need not be detrimental to a population with good recruitment from germlings or vegetative shoots growing under a dense canopy layer.

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.

The brown algaFucus serratusis a key foundation species on rocky intertidal shores of northern Europe. We sampled the same population off the coast of southern Norway in 2000 and 2008, and using 26 microsatellite loci, we estimated the changes in genetic diversity and effective population size (Ne). The unexpectedly lowNe(73–386) andNe/Nratio (10−3–10−4), in combination with a significant decrease (14%) in allelic richness over the 8-year period, suggests an increased local extinction risk. If smallNeproves to be a common feature ofF. serratus, then being abundant may not be enough for the species to weather future environmental changes.

Vegetative reproduction by means of abscised fragments was studied in the introduced red alga ‘‘Heterosiphonia japonica’’. Small side branches (pseudolaterals) are actively shed in all seasons, but mostly during late summer/autumn. The development of excised pseudolaterals was studied in the laboratory under different culture conditions. At 08C, few pseudolaterals survived and no development was observed. At 48C, survival was high but development was slow, while at 12 and 208C the majority of pseudolaterals developed rhizoids and attached to the substratum. Aquarium studies of fragmentation rate of pseudolaterals and estimates of tetraspore production showed that the instantaneous fecundity by fragments could be almost as high as the estimated fecundity by tetraspores. Field observations showed recruitment of ‘‘H. japonica’’ by fragments during all seasons. There was a weak trend of higher densities of recruits originating from fragments during late summer, consistent with the high degree of pseudolateral shedding and optimal temperature for pseudolateral development at this time of the year. The results from this study show that the newly introduced species has a high capacity for regenerating from small branchlets, and a continuous release of these vegetative propagules throughout the year.

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).