Jan Rueness

Sargassum muticum and other introduced Japanese macroalgae: Biological pollution of European coasts

Abstract The first finds of attached populations of the Japanese brown seaweed Sargassum muticum are reported from Norway. The rapid spread of this invasive species in Europe during the last 15 years is discussed. Other recent introductions of large brown algae caused by importation of Japanese oyster in mariculture include Undaria pinnatifida and Laminaria japonica. The ecological consequences of their spread are difficult to predict, but the changes they could bring about in the ecosystem are far more serious than the earlier well-known introductions of species belonging to the fouling community.

Life history and molecular sequences of Gracilaria vermiculophylla(Gracilariales, Rhodophyta), a new introduction to European waters

J. Rueness. 2005. Life history and molecular sequences of Gracilaria vermiculophylla (Gracilariales, Rhodophyta), a new introduction to European waters. Phycologia 44: 120–128. Gracilaria vermiculophylla, originally described from Japan, is reported for the first time from European waters where it appears to be restricted to sheltered, estuarine habitats as loose-lying, entangled mats on mud and fine sand, mostly in the vegetative state. The life history was completed in culture in an isolate from Brittany, France. Growth experiments demonstrated the euryhaline and eyrytherm nature of the alga with good growth at 11°C, 19.5°C and 25°C at salinities of 10, 20 and 30 psu, and best growth at 10 psu and 19.5°C. Specimens were sampled from 13 locations in Brittany. In addition, samples of unidentified Gracilaria sp. growing under similar environments were received from Sweden, the Netherlands, Spain and Portugal. Dried specimens of authentic G. vermiculophylla (G. asiatica) from Japan and Korea were examined using DNA sequence data. Mitochondrial DNA cox 2–3 spacer was sequenced in at least one individual from each locality and plastid DNA Rubisco spacer sequences were obtained from many. The rbcL sequence was obtained in the cultured clone, and was only partially sequenced (c. 50–60%) in a few others. No intraspecific variation was seen in the cox 2–3 and Rubisco spacers, and only one difference was seen in rbcL sequences. Isolates of G. gracilis and Gracilariopsis longissima were used for comparisons. It is concluded that the G. vermiculophylla populations in Europe are probably due to a recent introduction event. Some recent reports suggest that the species may also occur on both Atlantic and Pacific coasts of America.

The Baltic Sea as a model system for studying postglacial colonization and ecological differentiation, exemplified by the red alga Ceramium tenuicorne

The Baltic Sea provides a unique model system for studying genetic effects of postglacial colonization and ecological differentiation, because all marine organisms must have immigrated after the opening of the Danish Straits 8000 years ago and responded to the development of the steep Skagerrak‐Baltic salinity gradient. The red alga Ceramium tenuicorne shows conspicuous variation in growth and reproduction along this gradient. Herein we obtained reproductive data coupled with two types of molecular markers, one organellar (cox2–3 spacer sequences of mitochondrial DNA; mtDNA) and one mainly nuclear (random amplified polymorphic DNAs; RAPDs). Nine main populations were sampled in a nested spatial hierarchy including three salinity regions (Oslofjorden, Kattegat, and the Baltic Sea), and nine additional populations were sampled for the mtDNA analysis. Asexuality was frequent at low (Baltic) and medium (Kattegat) salinities but virtually absent at the highest salinity (Oslofjorden). Five mtDNA haplotypes were observed, of which two highly divergent ones were common. One was restricted to and fixed in Oslofjorden, and the other, which was closely related to the three rare haplotypes, was found from southernmost Norway via Kattegat into the Baltic. The RAPD data revealed, on the other hand, a continuous cline corresponding to the salinity gradient, with 27.4% divergence among salinity regions and most of the variation stored at the smallest spatial scale analysed (64.2%; within 1 m2 subpopulations). The combined data suggest colonization from a diverse Atlantic glacial gene pool followed by (1) lineage sorting of ancestral mtDNA polymorphisms and (2) strong differential selection among nuclear genotypes along the salinity gradient, including selection for nonrecombinant multiplication of those best fit to the marginal low‐salinity habitats.

Growth in culture of four red algae from Norway with potential for mariculture

There has been a rapid development of red algal mariculture during recent years (Hansen et al. 1981). Seaweed biomass conversion to fuels, and the use of red algae for nutrient-scrubbing purposes, are new applications in addition to the traditional utilization as a source for phycocolloids and for food.

Comparison of survival and growth in germlings of six fucoid species (Fucales, Phaeophyceae) at two different temperature and nutrient levels

During their initial post‐settlement period, fucoid germlings will be exposed to large variations in environmental factors such as temperature and nutrient concentration, which may influence survival and growth. Factorially designed culture experiments were used to compare the effects of temperature and nutrient concentration on the survival and growth of germlings in six fucoid species from the Norwegian Skagerrak coast. In four of the species (Ascophyllum nodosum, Fucus evanescens, F. serratus, and F. vesiculosus), survival did not differ between the two temperatures tested (7 and 17°C), whereas survival was reduced at 7°C in F. spiralis and Sargassum muticum. The effect of nutrient enrichment (seawater enriched with 32 μmol N and 2 μmol P per litre) on germling growth depended on the temperature regime, and differed little between species. The relative growth rate of germlings increased with increasing temperature in all six species and was higher in S. muticum (∼0.21 day ) than in the other fucoids (0.09–0.14 day ) at 17°C. At 7°C, F. serratus germlings had the highest relative growth rate (∼0.13 day ), whereas those of S. muticum and F. spiralis were reduced to ∼0.05 and ∼0.03 day , respectively. These results are in accordance with the reproductive season for the species, as germlings of the summer/autumn reproducers, F. spiralis and S. muticum, were less tolerant to low temperatures than the other Skagerrak fucoids whose reproduction occurs earlier in the year. Egg volume varied almost 10‐fold across species, from F. vesiculosus (smallest) to S. muticum (largest), and showed no correlation with relative growth rates or survival, wherease the size of germlings was positively related to egg volume after 15 days of cultivation under nutrient‐enriched conditions at 17°C. These results suggest that summer reproduction, larger eggs and a higher growth rate of germlings may give the introduced species, S. muticum, a competitive advantage.

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.

EFFECT OF CANOPY BIOMASS AND WAVE EXPOSURE ON GROWTH IN LAMINARIA HYPERBOREA (LAMINARIACEAE : PHAEOPHYTA)

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...

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).

Systematics of the marine microfilamentous green algae Uronema curvatum and Urospora microscopica (Chlorophyta)

The microfilamentous green alga Uronema curvatum is widely distributed along the western and eastern coasts of the north Atlantic Ocean where it typically grows on crustose red algae and on haptera of kelps in subtidal habitats. The placement of this marine species in a genus of freshwater Chlorophyceae had been questioned. Molecular phylogenetic analysis of nuclear-encoded small and large subunit rDNA sequences reveal that U. curvatum is closely related to the ulvophycean order Cladophorales, with which it shares a number of morphological features, including a siphonocladous level of organization and zoidangial development. The divergent phylogenetic position of U. curvatum, sister to the rest of the Cladophorales, along with a combination of distinctive morphological features, such as the absence of pyrenoids, the diminutive size of the unbranched filaments and the discoid holdfast, warrants the recognition of a separate genus, Okellya, within a new family of Cladophorales, Okellyaceae. The epiphytic Urospora microscopica from Norway, which has been allied with U. curvatum, is revealed as a member of the cladophoralean genus Chaetomorpha and is herein transferred to that genus as C. norvegica nom. nov.

Effects of temperature and salinity on growth, reproduction and survival in the introduced red alga Heterosiphonia japonica (Ceramiales, Rhodophyta)

Abstract We determined temperature and salinity responses in culture of a Norwegian isolate of the introduced red alga Heterosiphonia japonica. The species was eurythermal, surviving temperatures between 0°C and 30°C, with adult plants showing slightly higher temperature tolerance than carposporelings. Optimal growth conditions for carposporelings were 19–25°C and 30 psu. Growth rates at 20 psu and 30 psu did not differ significantly, but a marked reduction in the development of tetrasporangial stichidia was observed at 20 psu. At 15 psu, growth was poor and no stichidia were produced. Ten psu was lethal. Vegetative reproduction by fragmentation was common. Sporelings survived at least 40 days in darkness under various temperature conditions. The wide tolerance limits to temperature and salinity, high specific growth rates and effective propagation by fragmentation suggest that H. japonica will continue to disperse northwards and eastwards along the Norwegian coast, but that spread into the Kattegat and Baltic Sea will be controlled by low salinities and freezing winter temperatures. The life history of the Norwegian isolate was completed in culture, and a Polysiphonia type of life history was observed at 12°C and 17°C, whereas only tetrasporangial and vegetative specimens have been observed in field collections.