COLONIZATION AND GROWTH OF ASCOPHYLLUM NODOSUM (PHAEOPHYTA) IN MAINE1

Colonization and growth of Ascophyllum nodosum (L.) Le Jol. were investigated in two Maine estuaries from 1972 to 1978. Following denudation of intertidal rock, substrata were initially colonized by Fucus vesiculosus L.; eventually, Ascophyllum supplanted Fucus, and became dominant in terms of percentage cover. Ascophyllum settled first and most densely in the low intertidal zone, but its fastest growth occurred in the mid-intertidal zone. Some, but not all, Ascophyllum germlings produced a vesicle within one year of colonization. The mean annual growth of A. nodosum was variable among sites, zones and years.     

Phenolic Compounds in the Embryo Development of Several Northern Hemisphere Fucoids

Abstract: Light and electron microscopy were used to study the involvement of phenolic compounds in the early development of the Northern Hemisphere fucoids, Fucus serratus (L.), Fucus spiralis (L.) and Himanthalia elongata (L.) S. F. Gray. Phenolic compounds, packaged within physodes are a major cytoplasmic component of brown algae. Physodes accumulate at the zygote periphery early in development and are secreted into the primary zygote wall. At germination, physodes accumulate at the rhizoid tip. Physodes, together with other wall components, contribute to the development of the cell plate. Good evidence already exists for the involvement of phenolic compounds in the development of Southern Hemisphere fucoids, and this study shows that phenolics play a similar role in the Northern Hemisphere. Consequently, their perceived role as herbivore deterrents in Northern Hemisphere species may be a consequence of their role in wall construction.     

ISOLATION AND CHARACTERIZATION OF GOLGI APPARATUS FROM EGGS OF FUCUS (PHAEOPHYCEAE)1

A golgi-rich cell-free fraction has been obtained from eggs of Fucus serratus L. and characterized by enzyme markers (IDP-ase and TPP-ase) and electron microscopy. The results are correlated with cytochemical localization of IDP-ase and TPP-ase in situ.     

Arrested development in Fucus spiralis (Phaeophyceae) germlings exposed to copper

Exposure of Fucus spiralis germlings to precise copper concentrations (0 to 844?nM?Cu²⁺) in chemically defined medium demonstrated a relationship between ultrastructural changes and growth retardation with increasing copper concentration. Electron-translucent vesicles, present in ova, which normally disappear after fertilization, accumulated in germlings exposed to Cu²⁺ above 10.6?nM, suggesting that copper may inhibit a metabolic pathway involved in cell wall formation which is initiated by fertilization. No membrane damage was observed during the exposure period. During a post-exposure period in copper-free medium, recovery occurred (rhizoid extension, apical hair formation) in germlings previously exposed to concentrations below 106?nM?Cu²⁺ and electron-translucent vesicles became granular and disappeared. It is proposed that the electron-translucent vesicles contain a cell wall precursor and that copper inhibits its incorporation into the cell wall, preventing growth and development of the zygote.     

PATERNAL LEAKAGE OF MITOCHONDRIAL DNA IN A FUCUS (PHAEOPHYCEAE) HYBRID ZONE1

Eukaryotic mitochondria are mostly uniparentally (maternally) inherited, although mtDNA heteroplasmy has been reported in all major lineages. Heteroplasmy, the presence of more than one mitochondrial genome in an individual, can arise from recombination, point mutations, or by occasional transmission of the paternal mtDNA (=paternal leakage). Here, we report the first evidence of mtDNA paternal leakage in brown algae. In Denmark, where Fucus serratus L. and Fucus evanescens C. Agardh have hybridized for years, we found eight introgressed individuals that possessed the very distinct haplotypes of each parental species. The finding of heteroplasmy in individuals resulting from several generations of backcrosses suggests that paternal leakage occurred in earlier generations and has persisted through several meiotic bottlenecks.     

THE RELEASE OF COPPER-COMPLEXING LIGANDS BY THE BROWN ALGA FUCUS VESICULOSUS (PHAEOPHYCEAE) IN RESPONSE TO INCREASING TOTAL COPPER LEVELS

The growth of Fucus vesiculosus L. germlings in chemically defined culture media containing a range of Cu concentrations (20–1000 nM) was monitored simultaneously with measurement of the Cu speciation in the media by competitive equilibrium-adsorptive cathodic stripping voltammetry. Fucus vesiculosus germlings were found to exude Cu-complexing ligands with conditional stability constants of the order of 1.6 × 10¹¹. Ligand concentrations increased with increasing total dissolved Cu concentrations (Cu_T) until a concentration of 500–800 neq Cu·L⁻¹ was reached. Concentrations of the ligand exceeded Cu_T in treatments containing 20 and 100 nM Cu, were similar to Cu_T in the 500-nM Cu treatment, but were less than Cu_T in the 1000-nM treatment. Therefore, [Cu²⁺] were calculated to be at concentrations of 10⁻¹¹− 10⁻¹⁰ M in the 20- and 100-nM treatments, 10⁻⁹ M in the 500-nM treatment, and 10⁻⁷ M in the 1000-nM treatment. Growth rates were lowest at Cu²⁺ concentration > 10⁻⁹. These results are discussed within the context of the potential roles for exuded copper-complexing ligands.     

THE FUCUS (PHAEOPHYCEAE) SPERM RECEPTOR FOR EGGS. I. DEVELOPMENT AND CHARACTERISTICS OF A BINDING ASSAY1

To explore the molecular basis of egg-sperm recognition in the brown alga , Fucus serratus L., we developed an in vitro binding assay involving egg plasma membrane vesicles (PMVs) and proteins contained in a KCl extract of sperm. Binding between the two components was measured using biotinylated PMVs followed by the addition of streptavidin conjugated to alkaline phosphatase and the appropriate substrate. Biotinylation did not affect the ability of egg PMVs to inhibit fertilization in a species-preferential manner. Binding of labeled egg PMVs to the sperm KCl extract was saturable and competable with unlabeled PMVs but was not species-specific. Protease treatment of the KCl extract abolished binding, whereas periodate had no effect, suggesting that sperm protein rather than carbohydrate was involved. Preincubation of the sperm extract with sulfated polysaccharides (e.g. fucoidan and ascophyllan) inhibited binding of egg plasma membranes. Sulfation seems to be important for this effect since desulfated fucoidan was far less effective at blocking binding. Polysaccharides which inhibited binding also inhibited fertilization. Overall, the results indicate that at least some aspects of binding between Fucus sperm and eggs are mediated by a protein(s) derived from sperm which recognizes sulfated glycoconjugates on the egg plasma membrane .     

Interaction between isopod grazing and wave action: a structuring force in macroalgal communities in the southern Baltic Sea

The macroalgal belt in the southern Baltic Sea may be partly structured by the interaction of physical and biological factors. A field study, spanning the 1990s, describes a rapid decline of the Fucus spp. stands along the wave-exposed Swedish southeast coast. During this period, a relative dominance of Fucus vesiculosus L. shifted to a relative dominance of Fucus serratus L. The decline of F. vesiculosus coincided with observations of large numbers of the grazing isopods Idotea baltica (Pallas) and Idotea granulosa Rathke, or with field observations of frequent grazing marks on Fucus fronds. I. baltica, but not I. granulosa, tended to aggregate in the declining Fucus spp. stands, indicating a strong preference for Fucus spp. In a mesocosm experiment I. baltica, when given a choice, grazed both Fucus species at weak water motion. At strong water motion grazing was concentrated on F. vesiculosus. It is hypothesized that one of the reasons I. baltica preferred F. vesiculosus to F. serratus at strong water motion may have been differences in habitat quality, like width of thallus, influencing the ability to cling to the plant. Smaller thallus, as in F. vesiculosus, thus is the preferred habitat for grazing of I. blatica. We postulate that the existence of F. serratus in the area may be favoured by strong wave action and moderate but not strong grazing by I. baltica, relaxing the interspecific competition from F. vesiculosus.     

REACTIVE OXYGEN PRODUCTION AND DAMAGE IN INTERTIDAL FUCUS SPP. (PHAEOPHYCEAE)

The research described in this paper was designed to test the hypothesis that the differential stress tolerance associated with the vertical zonation of intertidal seaweeds is attributable to reactive oxygen metabolism. To do so, we measured the production of, and damage caused by, reactive oxygen in three species of intertidal brown seaweeds— Fucus spiralis L., F. evanescens C. Ag., and F. distichus L.— that differ in their ability to withstand freezing, desiccation, and high light stress. Fucus spiralis is the most stress-tolerant species and F. distichus the least. Reactive oxygen production was determined by measuring the production of H₂O₂ and the oxidation of dichlorohydrofluorescein diacetate to dichlorofluorescein. Damage caused by freezing, desiccation, and high-light stress was assessed by measuring variable fluorescence (F_v/F_m) and lipid peroxidation. Production of reactive oxygen increased following freezing, desiccation, or high-light stress. In general, the data were consistent with the hypothesis that reactive oxygen metabolism is involved in stress tolerance. The production of reactive oxygen was relatively low in unstressed seaweeds, and there was little difference between species. Fucus distichus showed the greatest increase in reactive oxygen production after desiccation and freezing stress. Fucus evanescens produced more reactive oxygen production after desiccation than F. spiralis. Although F. evanescens and F. spiralis produced similar amounts of reactive oxygen after freezing, this treatment resulted in an increase in lipid peroxidation only in F. evanescens (and F. distichus ).     

FLUORESCENCE EMISSION SPECTRA OF MARINE AND BRACKISH‐WATER ECOTYPES OF FUCUS VESICULOSUS AND FUCUS RADICANS (PHAEOPHYCEAE) REVEAL DIFFERENCES IN LIGHT‐HARVESTING APPARATUS1

The Bothnian Sea in the northerly part of the Baltic Sea is a geologically recent brackish‐water environment, and rapid speciation is occurring in the algal community of the Bothnian Sea. We measured low‐temperature fluorescence emission spectra from the Bothnian Sea and the Norwegian Sea ecotypes of Fucus vesiculosus L., a marine macroalga widespread in the Bothnian Sea. Powdered, frozen thallus was used to obtain undistorted emission spectra. The spectra were compared with spectra measured from the newly identified species Fucus radicans Bergström et L. Kautsky, which is a close relative of F. vesiculosus and endemic to the Bothnian Sea. The spectrum of variable fluorescence was used to identify fluorescence peaks originating in PSI and PSII in this chl c–containing alga. The spectra revealed much higher PSII emission, compared to PSI emission, in the Bothnian Sea ecotype of F. vesiculosus than in F. radicans or in the Norwegian Sea ecotype of F. vesiculosus. The results suggest that more light‐harvesting chl a/c proteins serve PSII in the Bothnian Sea ecotype of F. vesiculosus than in the two other algal strains. Treatment of the Bothnian Sea ecotype of F. vesiculosus in high salinity (10, 20, and 35 practical salinity units) for 1 week did not lead to spectral changes, indicating that the measured features of the Bothnian Sea F. vesiculosus are stable and not simply a direct result of exposure to low salinity.     

Effect of fucoidan from brown alga <Emphasis Type="Italic">Fucus evanescens</Emphasis> on a formation of TMV-specific inclusions in the cells of tobacco leaves

The effect of fucoidan (1.3; 1.4-α-L-fucan), a sulfated polysaccharide from the brown alga Fucus evanescens on the formation of specific granular and tubular inclusions induced by tobacco mosaic virus (TMV) and consisted presumably of the virus-coded protein components of the viral replicase was investigated in the TMV-infected leaves of tobacco (Nicotiana tabacum L.). In four days after inoculation of the leaves with a TMV preparation (1 mg/ml), the signature of infection in a presence of fucoidan (1 mg/ml) was a preferential formation of intracellular granular inclusions, which were related to early stages of the virus reproduction. When infected leaves were not treated with fucoidan, their cells contained mainly tubular inclusions, which were presumably formed from the granular ones on the last stages of the infection process. These observations demonstrated that fucoidan delayed the development of the TMV-induced infection.     

FREEZE FRACTURE STUDY OF THYLAKOIDS OF FUCUS SERRATUS1

Freeze-fractured thylakoids of Fucus serratus L. exhibit three types of faces with a particle density analogous to that of EFs, EFu and PF faces of green plants. However the particle size distribution is unimodal in the three types with a mean of about 8 nm. No obvious distinction between PFs and PFu faces could be detected. The absence on EFs faces of the distinct class of large particles (>13 nm) existing in green plant thylakoids implies a unique organization of pigment proteins, especially of the light-harvesting complexes.     

Hybridization and introgression in a mixed population of the intertidal seaweeds Fucus evanescens and F. serratus

The introduced Fucus evanescens (hermaphroditic) and the native F. serratus (dioecious) have been in secondary contact along the Danish coast of the Kattegat Sea for 60–100 years and dioecious hybrids have been observed at Blushøj for several years. Hybridization in Fucus is unusual because it appears to always involve a hermaphroditic and a dioecious parental pair. We determined the degree and spatial patterns of introgression for 286 individuals using 10 microsatellite loci and cpDNA. Hybrids accounted for nearly 13% of the population, yet parental species were well differentiated (F_ST = 0.633). The presence of F. evanescens chloroplasts in 100% of F₁ hybrids revealed asymmetrical hybridization. Fucus evanescens cpDNA was observed in 50% of introgressed and 5.4% of pure F. serratus, but no F. serratus cpDNA was found in F. evanescens. In contrast, nuclear DNA introgression was symmetrical with an equal amount (≈1.5%) of genes introgressed into each parental species. Survivorship and viability data suggest selection against hybrids in the hybrid zone.     

Isolation of protoplasts from Fucus serratus and F. vesiculosus(Fucales, Phaeophyceae): factors affecting protoplast yield

Protoplasts were isolated enzymatically from meristematic tissues of the brown algae, Fucus serratus, using a combination of 2% cellulase R-10 Onozuka, 0.5% macerozyme and 1% crude extract of gland gut of Aplysia vaccaria. The main factors affecting protoplast yield were identified. Protoplasts were produced in large quantities from apical region of thallus and from plantlets compared to mature explants. Yields were greatly improved by the addition of sodium citrate and bovine serum albumin in the enzymatic solution and could reach 5.8 × 10⁶ protoplasts per gram of fresh wt. The applicability of these optimal parameters to other species Fucus vesiculosus was shown.     

AMINO ACID SEQUENCE ANALYSIS OF THE SMALL SUBUNIT OF RIBULOSE BISPHOSPHATE CARBOXYLASE FROM FUCUS (PHAEOPHYCEAE)1

This paper reports for the first time amino acid sequence information for the small subunit of ribulose-1,5-bisphosphate carboxylase / oxygenase (Rubisco) from a non-green alga. N-terminal sequences are presented for the polypeptide from three species of the genus Fucus (Phaeophyceae). Although homologous to small subunit polypeptides from other organisms, the Fucus sequences exhibit a unique N-terminal section resembling neither cyanobacterial nor chlorophytic sequences. This difference may be a consequence of the plastid DNA coding arrangement for the small subunit in chromophytes, a situation reported for the related organism Olisthodiscus but not previously investigated at the amino acid sequence level.     

The Effect of Elevated UV Radiation on Fucus spp. (Fucales,Phaeophyta) Zygote and Embryo Development

Abstract: This study has shown that in Fucus serratus and Fucus distichus, young zygotes and embryos are highly susceptible to elevated levels of both UVA (UVAR) and UVB radiation (UVBR). Zygotes treated with UVAR are able to polarise and germinate, but are very slow to divide; if they do, they often have skewed division planes or deformed rhizoids. Those treated with UVAR and UVBR remain spherical, they do not polarise, germinate to form rhizoids or undergo cell division. We suggest that the UVR may be affecting the cytoskeleton. Conversely, zygotes and embryos of Fucus spiralis are able to withstand these same UVR levels and, at the light microscope level, appear to develop normally. When the brown algal phenolic compound phloroglucinol was placed in a filter covering the developing embryos, normal development was seen under all treatments. Phenolic compounds protect the developing fucoids from UVR. In comparison with the other two species, Fucus spiralis grows high up on the shore and is exposed for much longer periods of time and, presumably, to higher levels of natural UVR. The failure of the juvenile stages of F. serratus and F. distichus to withstand UVR stress may have implications for the continued survival of these species in the intertidal, and may prove detrimental to the population as a whole if UVR levels increase.     

FACTORS AFFECTING SURFACE ALKALINE PHOSPHATASE ACTIVITY IN THE BROWN ALGA FUCUS SPIRALIS AT A NORTH SEA INTERTIDAL SITE (TYNE SANDS,SCOTLAND)1

Surface alkaline phosphatase activity (APA) was measured in the tips of Fucus spiralis L. thalli over an approximately 1-year period, using small plants from upper littoral rock pools at a site on the east coast of Scotland. Maximum APA (4.4 μmol p-NP·g dry wt^?1·h^?1) occurred in April, coincident with a sharp increase in tissue N:P ratio of the tips and the probable period of most rapid growth. Enzymatic activity was not correlated with any of the physical and chemical factors (temperature, pH, external phosphate, salinity) measured in the pools or nutrient concentrations (C, N, P) in the apical part of the thallus. No obvious correlation was found between APA and the position of a plant on the shore. However, APA was significantly higher in plants emersed at low tide than in plants submerged during the whole tidal cycle. There was a significant positive correlation between APA and tissue P within a single thallus, with the highest value at the tip (which includes the meristematic zone). Changes in APA of Fucus spiralis appear to result from a complex interaction of biotic and environmental factors, including stress by emersion, growth period, rapid changes in tissue nutrient content and N:P ratio, and regzon of thallus.     

INHIBITION OF CARBON UPTAKE AND STIMULATION OF NITRATE UPTAKE AT LOW SALINITIES IN FUCUS DISTICHUS (PHAEOPHYCEAE)1

Inorganic carbon and nitrate uptake were examined in whole plants of Fucus distichus L. (Powell) incubated in dilutions of synthetic ocean water and media with different concentrations of Na⁺, K⁺ and Cl^?. Reduction in salinity from normal seawater (33 ppt) decreased carbon uptake rate but increased nitrate uptake rate by 50% each. Substitution of K⁺ for Na⁺ at constant ionic strength decreased nitrate uptake. Substitution of K⁺ or mannitol for Na⁺ decreased carbon uptake. Neither the uptake of nitrate or carbon was changed by substituting SO₄^2- for Cl^?. Ionophores, valinomycin and monensin, inhibited both nitrate uptake and carbon fixation from 20 to 70% of control rates. The stimulation of nitrate uptake at low salinity may be beneficial to plants in estuarine tidal environments in which nitrate is supplied by the fresh water source.     

Changes in Endogenous Fatty Acids and Lipid Synthesis Associated with Copper Pollution in Fucus spp

Fatty acid synthesis from [¹⁴C]acetate was studied in the brownalgae, Fucus serratus and Fucus vesiculosus, which had beencollected from sites polluted by run-off from old copper mines.Algae collected from areas exposed to copper in situ showedchanges in the pattern of fatty acids labelled in vitro withan increase in oleate labelling and a decrease in palmitatelabelling in both species. The endogenous fatty acid patternsfor algae from polluted sites also differed from those fromunpolluted sites. Algae from sites polluted by copper containedmore oleate than samples from non-polluted sites. In addition,there were decreases in the polyunsaturated fatty acids -linolenate,octadecatetraenoate and docosapentaenoate for copper-exposedalgae. These differences are discussed with regard to the possiblemetabolic site of copper's action and to the relative toleranceof Fucus spp. to high environmental dissolved copper levels. Key words: Fucus spp., Copper pollution, Fatty acid synthesis     

Research note: Salinity tolerance of Arctic kelps from Spitsbergen

The effect of hypo‐ and hypersaline treatments on the effective quantum yield of photosystem II was comparatively studied with a pulse amplitude modulated fluorometer (PAM) in the brown algal species Alaria esculenta, Fucus distichus, Laminaria digitata, Laminaria solidungula, Saccharina latissima (formerly Laminaria saccharina) and Saccorhiza dermatodea collected in the Arctic Kongsfjorden (Spitsbergen). While the euryhaline F. distichus was not affected at all by salinities ranging from 5 to 60 psu, A. esculenta, S. latissima and L. solidungula exhibited under hyposaline conditions strong loss of pigments (bleaching) or even high mortality reflecting stenohaline features. In contrast to the latter species, L. digitata and S. dermatodea survived all salinities, but showed reduced photosynthetic activities at the lowest and highest salt treatments and hence, can be characterized as stenohaline‐euryhaline organisms. The data are discussed in terms of vertical zonation (eulittoral versus sublittoral habitat), in terms of interactive effects with other abiotic factors such as temperature and in terms of the species‐specific acclimation potential.