Fucus Species Research Articles

Interspecific competition between Enteromorpha (Ulvales: Chlorophyceae) and Fucus (Fucales: Phaeophyceae) germlings: effects of nutrient concentration, temperature, and settlement density

The increased abundance of ephemeral algae and corresponding decline in perennial fucoids observed in eutrophic (nutrient-rich) waters could be caused by eutrophication-driven shifts in the competitive relationship between the 2 groups as early as the germling stage. During the initial post-settlement period germlings are exposed to large temporal variations in temperature, which may influence their performance and competitive interactions. Effects of temperature, nutrient concentration, and settlement density on the competitive relationship between germlings of Fucus serratus L. and F. evanescens C. Agardh and of the ephemeral alga Enteromorpha compressa (Linnaeus) Greville were examined using factorially designed culture experiments. In monocultures, germling growth of both Fucus species and E. compressa was generally stimulated by nutrient enrichment (32 pmol nitrate/ammonia and 2 μmol phosphate l -1 seawater) and high temperature (17°C compared to 7°C), and negatively related to settlement density (10 to 50 germlings cm -2 for Fucus, 30 to 130 germlings cm -2 for E. compressa). In mixed cultures, interspecific competition effects of E. compressa on F. serratus and F. evanescens germlings increased with increasing nutrient and temperature levels. In the nutrient-enriched cultures, interspecific competition from E. compressa suppressed the yield of Fucus spp. by 80 to 100% at 17°C, with F. evanescens being more suppressed than F. serratus, whereas the suppressive effects of E. compressa on Fucus germlings were <60% at 7°C. These results suggest that competition from ephemeral algae at early life stages may be a reason for the decline of fucoids in eutrophic waters and that reproduction at low temperatures, as in species like F. serratus and F. evanescens, may shield the vulnerable initial germling stages from the severest competition pressure by ephemeral algae.

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.

Chemical settlement inhibition versus post-settlement mortality as an explanation for differential fouling of two congeneric seaweeds.

It has been proposed that seaweed secondary metabolites, e.g. brown algal phlorotannins, may have an ecologically important function as a chemical defence against epiphytes, by acting against colonisation of epiphytic organisms. We tested whether the low epiphytic abundance on the invasive brown seaweed Fucus evanescens, compared to the congeneric F. vesiculosus, is due to a more effective chemical defence against epiphyte colonisation. A field survey of the distribution of the common fouling organism Balanus improvisus (Cirripedia) showed that the abundance was consistently lower on F. evanescens than on F. vesiculosus. However, contrary to expectations, results from experimental studies indicated that F. vesiculosus has a more effective anti-settlement defence than F. evanescens. In settlement experiments with intact fronds of the two Fucus species, both species deterred settlement by barnacle larvae, but settlement was lower on F. vesiculosus both in choice and no-choice experiments. Phlorotannins from F. vesiculosus also had a stronger negative effect on larval settlement and were active at a lower concentration than those from F. evanescens. The results show that Fucus phlorotannins have the potential to inhibit settlement of invertebrate larvae, but that settlement inhibition cannot explain the lower abundance of the barnacle Balanus improvisus on F. evanescens compared to F. vesiculosus. Assessment of barnacle survival in the laboratory and in the field showed that this pattern could instead be attributed to a higher mortality of newly settled barnacles. Observation suggests that the increased mortality was due to detachment of young barnacles from the seaweed surface. This shows that the antifouling mechanism of F. evanescens acts on post-settlement stages of B. improvisus.

DIFFERENCES IN LIFE‐HISTORY CHARACTERISTICS ARE CONSISTENT WITH THE VERTICAL DISTRIBUTION PATTERN OF FUCUS SERRATUS AND FUCUS VESICULOSUS (FUCALES, PHAEOPHYCEAE) IN THE CENTRAL BALTIC SEA

On the rocky shores of southeast Sweden, in the central Baltic Sea, the brown seaweed species Fucus serratus L. and Fucus vesiculosus L. form dense constantly submerged stands. The relative proportion of the two species in the belt is shifting both vertically and geographically. Our hypothesis is that differences in life‐history characteristics and the tolerance to physical factors such as wave force, freezing, and light may alter the competitive outcome between the two species with increasing wave exposure. This study included a combination of field studies and laboratory experiments. In sheltered locations, F. serratus and F. vesiculosus grow in mixed stands from 0.5 to 3 m deep, whereas at exposed sites F. vesiculosus grow from 0.5 to 2 m deep and F. serratus mainly from 1 to 5 m deep. The two Fucus species differed markedly in their tolerance to physical stress as well as in a number of reproductive and vegetative characteristics. Tolerance to freezing and wave action was higher in F. vesiculosus compared with F. serratus. Fucus vesiculosus also produced 10 times more eggs per receptacle, allocated significantly more tissue per frond for reproduction, and produced more reproductive fronds per individual than did F. serratus. In addition, the survival rate of F. vesiculosus germlings was slightly higher than that of F. serratus germlings during the first year. These differences in life history characteristics are suggested to partly explain the observed distribution patterns of the two Fucus species in the Baltic Sea.

Do monospecific stands of three Fucus species (Phaeophyta) comply with the ‘self-thinning rule’?

Development of biomass and density in experimental monospecific stands of Fucus serratus, F. vesiculosus and F. spiralis was followed on Helgoland (southern North Sea) in plots with three different initial germling densities. As biomass increased over time, considerable mortality occurred. Mortality was significantly higher in stands with higher initial densities, leading to similar final densities. The self-thinning law, which describes boundary conditions for combinations of biomass and density of plants, was refuted in two ways for all three Fucus species: (i) several data points on a bi-logarithmic plane lay considerably above self-thinning lines with conventional parameters from terrestrial plant ecology; however, ‘overall boundaries’ (i.e. a self-thinning line that constrains all lines found) from terrestrial plant ecology were not significantly transgressed, (ii) lines fitted with principal components analysis (PCA) revealed a positive correlation between stand biomass and density. Reasons are proposed why seaweeds generally seem to show higher maximum biomass for a given density than terrestrial plants. Size distributions at the end of the experiment were positively skewed with high Gini coefficients that lay in the range found in other seaweed studies. Inequality decreased with individual mass and increased with density. Gini coefficients were highly correlated with other measurements of inequality (coefficient of variation, skewness).

Competitive ranks of three Fucus spp. (Phaeophyta) in laboratory experiments?testing of Keddy's competitive hierarchy model

Keddy's competitive hierarchy model describes species distribution patterns along gradients under equilibrium conditions and can potentially serve as an explanation for zonation patterns of intertidal seaweeds on rocky shores. One of the assumptions of the model is a competitive hierarchy with the top competitor occupying the benign end of the gradient. Another assumption is the consistency of competitive ranks of species in all environmental conditions included in the shared parts of species' fundamental niches. In laboratory replacement series experiments, the competitive ranks of pairs of Fucus species that occupy adjacent zones in the field were analysed and compared to ranks found in previous field experiments. Unattached thalli of Fucus serratus versus F. vesiculosus or F. vesiculosus versus F. spiralis, respectively, were held in aerated beakers to establish the competitive ranking of the three congeners. Each replacement series was conducted at three total densities. F. vesiculosus was clearly competitively dominant over F. serratus. In competition with F. spiralis, F. vesiculosus was only dominant at its lowest absolute input frequencies, but at higher frequencies dominance was reversed. At high densities, the total ranking was F. spiralis > F. vesiculosus > F. serratus, which is the opposite order to that which would be expected from Keddy's model. Although all three species thrived well under the laboratory conditions, the results did not reflect in situ competitive dominances, which may be an effect of nutrient competition in the laboratory. Keddy's assumption that competitive ranks are consistent over the whole range of fundamental niches cannot be supported for Fucus spp.

Mechanisms of range expansion in the intertidal brown alga Fucus serratus in northern Spain

The intertidal brown alga Fucusserratus is naturally expanding its distributional range along the north shore of Spain. Shores being colonised by F. serratus harbour saturated algal communities, with almost no free space. Processes responsible for the successful expansion were investigated in a locality where the alga was experimentally introduced. After a short period, the number of F. serratus plants increased exponentially at a monthly intrinsic rate of 0.111. At early and intermediate stages of invasion, colonisation occurred by the growth of patches of the invader around the transplant points. F. serratus is a bad disperser, with most of propagules settling in near proximity to parent plants. Colonisation of manipulated and control areas was influenced by the proximity of propagule sources. Experimental removals of canopies, irrespective of whether the turf was removed or left intact, accelerated the expansion, as this component of the community had a negative influence on recruitment of both F. serratus and F. vesiculosus. The unmanipulated algal beds were, however, invasible, as some control quadrats close (<10 m) to F. serratus patches had a 100% cover of F. serratus at the end of the study. Prior or concurrent to increases of F. serratus, a decrease in cover of F. vesiculosus and other resident macroalgae was evident. No formal competition experiment was done but results suggest that F. serratus outcompetes F. vesiculosus and Bifurcariabifurcata at mid-tidal levels. In scraped quadrats, in which both Fucus species recruited at large densities, F. serratus grew at a higher rate than F. vesiculosus and eventually monopolised the experimental surfaces.

Effects of UV radiation and temperature on growth of germlings of three species of Fucus (Phaeophyceae)

Measurements of relative growth rates (RGR) of germlings of three species of Fucus (Fucales, Phaeophyceae) collected in Helgoland (North Sea, Germany) were carried out in the laboratory in order to determine the effects of different ultraviolet radiation (UVR, λ=280–400 nm) conditions, UVR doses and temperatures. High ultraviolet-B radiation (UVBR, λ=280–315 nm) levels and low temperature, as independent factors, led to a species-specific reduction in RGR which appears to be related to the vertical distribution of the species in the intertidal zone. The inhibition of RGR ranged from 10% to even death of the germling. For the most sensitive species, high temperature in combination with a high dose of UVBR caused the death of the germlings, whereas at low temperature germlings were able to survive. This suggest growth-related temperature dependence of sensitivity to UVBR.

Establishment of the Exotic Species Fucus evanescens C. Ag. (Phaeophyceae) in öresund, Southern Sweden

The spread and establishment of the exotic species Fucus evanescens in oresund, Southern Sweden was documented through inventories in 1966–72 and 2000. The species spread fast from the first known ...

Nitrate and phosphate uptake characteristics of three species of brown algae cultured at low salinity

Nitrate and phosphate uptake mechanisms have been characterised under conditions of 100 and 50% seawater in 3 common brown algae of NW Europe: Fucus vesiculosus, F. serratus and Laminaria digitata. Under low salinity, the growth rate and internal nitrate accumulation of F. serra- tus significantly increased (20 and 48%, respectively), but no significant changes were observed for F. vesiculosus and L. digitata. However, nitrate uptake rates were reduced in L. digitata, so that this species was less adaptable to low salinity than the Fucus species. Both F. vesiculosus and F. serratus reached a steady-state uptake rate after acclimation regardless of the salinity treatment. All 3 species had a high capacity for storing inorganic N and P intracellularly. The results for F. serratus pointed to a dual mechanism of adaptation to the special characteristics of the intertidal environment where it grows. Non-saturating (low affinity) nitrate uptake and biphasic (double Michaelis-Menten curve) phosphate uptake are adaptations to high nutrient concentrations. Temporal partition of cellular energy for carbon metabolism and nutrient uptake is also suggested as an adaptation to the transient nutrient inputs occurring in these environments.

Density dependent grazing effects of the isopod Idotea baltica Pallas on Fucus vesiculosus L in the Baltic Sea

In the Baltic Sea, abiotic factors are often supposed to explain the distribution of the key species Fucus vesiculosus. Still, in many areas, decline of F. vesiculosus has coincided with mass occurrence of the herbivorous isopod Idotea baltica. The aim of this work was to examine whether, how and at what densities I. baltica can affect the distribution of F. vesiculosus in the central Baltic proper. Both large-scale field surveys and a two-week grazing experiment have been performed.

Effects of solar radiation on growth, photosynthesis and respiration of marine macroalgae from the Arctic

The effect of artificial ultraviolet (UV) and natural solar radiation on photosynthesis, respiration and growth was investigated in 14 red, green and brown macroalgal species on Spitsbergen (Norway) during summer 1998. In June, maximum mean solar radiation at sea level was 120 W m -2 of visible (370 to 695 nm) and 15 W m -2 of UV radiation (300 to 370 nm), and decreased gradually until the end of the summer. In spite of incident irradiance, levels were low in comparison with other latitudes, and UV radiation stress on growth of Arctic macroalgae was evident. Transplantation experiments of plants from deeper to shallow waters showed, for most algae, an inhibitory effect of both UVA and UVB on growth, except in the intertidal species Fucus distichus. The growth rate of selected macroalgae was directly correlated to the variations in natural solar radiation during the summer. Underwater experiments both in situ and using UV-transparent incubators revealed a linear relationship between the depth distribution and the growth rate of the algae. In almost all species the photosynthetic oxygen production decreased after 2 h incubation in the laboratory under 38 μmol m -2 s -1 photosynthetic active radiation (PAR 400 to 700 nm) supplemented with 8 W m -2 UVA (320 to 400 nm) and 0.36 W m -2 UVB (280 to 320 nm) compared to only PAR without UV. Like in the growth experiments, the only exception was the brown alga F. distichus, in which photosynthesis was not affected by UV. The degree of inhibition of photosynthesis showed a relation to the depth distribution, i.e. algae from deeper waters were more inhibited than species from shallow waters. In general, no inhibitory UV effect on respiratory oxygen consumption in all macroalgae studied was detected under the artificial radiation regimes described above, with the exception of the brown alga Desmarestia aculeata and the green alga Mono-stroma arcticum, both showing a significant stimulation of respiration after 2 h of UV exposure. The ecological relevance of the seasonal variations in the solar radiation and the optical characteristics of the water column with respect to the vertical zonation of the macroalgae is discussed.

A Competitive Hierarchy Model Integrating Roles of Physiological Competence and Competitive Ability Does Not Provide a Mechanistic Explanation for the Zonation of Three Intertidal Fucus Species in Europe

It has been clear for the last 20 yr that both competitive ability and physiological competence on the intertidal gradient of rocky shores determine the zoned distribution of fucoid seaweeds in the North Atlantic. However to this point, there has been no concept integrating these functions for seaweed vegetation in a single mechanistic explanation. Keddy's competitive hierarchy model, which has not been tested in marine systems (i.e. not on seaweed vegetation) provides an explanation for the zonation of plant species on environmental gradients. The model proposes that competitive abilities of species on a stress or resource gradient are inversely related to fundamental niche breadths. We tested 2 assumptions of the model to determine whether it provided a comprehensive explanation of zonation of 3 Fucus species on the island of Helgoland in the North Sea. The 2 assumptions translate into specific predictions for the Fucus assemblage (where F. serratus occurs on the low shore, F. spiralis on the high shore, and F. vesiculosus in between): I. competitive ranking is F. serratus > F. vesiculosus > F. spiralis; 2. fundamental niche breadth rankings are the reverse of competitive ability rankings. Pairwise competition experiments were done in the field. A highly modified substitutive design was used, in order to take into account the shortcomings of this approach. The empirically derived competitive hierarchy did not fit prediction I. Transplant experiments with adults and juveniles provided results contrary to prediction 2. Since none of the assumptions of the model fit, it cannot be used to provide a mechanistic explanation for the zonation of Fucus species on Helgoland. Unlike other important models of competition, Keddy's approach does not claim universal validity in all communities. This means that it requires empirical testing in each species assemblage, and more importantly, that the negative outcome reported here does not invalidate the concept in general.

Low divergence in rDNA ITS sequences among five species of Fucus (Phaeophyceae) suggests a very recent radiation.

Sequences from the two ribosomal DNA internal transcribed spacers (ITS1 and ITS2) were compared among five species of Fucus. Based on the present taxon sampling, parsimony analysis showed that Fucus serratus is the sister-group of the remaining Fucus species when Ascophyllum nodosum was used as an outgroup. The topology of the tree was (Fucus serratus (F. lutarius (F. vesiculosus (F. spiralis + F. ceranoides)))). The extremely low variation observed suggests a very recent radiation of the genus which supports the view widely accepted that the Fucales are among the most evolutionarily advanced of the brown algae. We further note that sequence differences between Fucus and Ascophyllum were 28%: this does not rule out the utility of ITS sequences within the Fucaceae. The very low number of informative positions allows to demonstrate empirically that distance matrix methods group on the basis of symplesiomorphies.

4 Symmetry Breaking in the Zygotes of the Fucoid Algae: Controversies and Recent Progress

Despite its many advantages as an experimental system for the study of the epigenesis of polarity, it is obvious that the fucoid zygote also presents many problems. The development of polarity proceeds largely independently of direct gene action and thus may be considered a problem in cellular physiology. Ca2+ appears to play an important role in the process, but the optical properties of the zygotes (opacity and autofluorescence) hamper the use of modern methods of visualizing the distribution of Ca2+ and other ions. Likewise, other approaches, such as injection of fluorescent-labeled G-actin, in order to study the dynamics of actin filaments, are subject to the same limitations. It may be that the application of two-photon microscopy will enable experimenters to avoid some of these problems. This technique uses excitation wavelengths that are twice the wavelength of maximum absorption by fluorophores, and sufficient photon density for absorption is achieved only in a thin section. The fucoid zygotes are considerably more transparent to longer wavelengths, so attenuation of the exciting light and autofluorescence should be significantly reduced. Perhaps we will then be able to see further into these opaque cells. Another problem concerns the use of different species and genera. This may be unavoidable; for example, those of us who are land-locked tend to rely on Pelvetia, as it travels and stores better than the various species of Fucus and is less seasonal. Our colleagues fortunate enough to work near the ocean prefer to use the species that are locally available. Nevertheless, it is important to be careful about cross-genus and cross-species generalizations. While it is unlikely, based on what we know, that there are fundamental differences in physiological mechanisms among species, there may be small but still important differences in details. Obviously, investigators should directly compare results in more than one species whenever possible. The area of greatest disagreement, perhaps, concerns the mechanism of polarity formation, as opposed to its overt manifestation, germination. Are Ca2+ and actin involved or not? Assuming Ca2+ is involved, is the source internal or external? One basis for the different findings may be the differences in the strength of the polarizing signal provided to the zygotes. Clearly, the cells have powerful mechanisms for amplifying a faint asymmetry and developing an axis in response to an external signal. Furthermore, the fucoids generally develop in the intertidal zone and thus must be adapted to meeting the challenge of a widely varying external environment. They may have alternate mechanisms for responding to unilateral light. We have adopted the approach of presenting the cells with a fairly weak light signal--the minimum required to induce a considerable degree of organization of a population of zygotes. We then determine the effects of various inhibitors on photopolarization. One advantage of this approach is that it has allowed us to find treatments that increase the sensitivity of the zygotes to light, something that would not be possible if the untreated controls were fully polarized. Some of the differences between our results and those of others may be related to their use of a stronger light stimulus. It may be that if given a strong stimulus, a sufficient trace is left in the cells so that they can organize an axis when an inhibitor is removed. Careful consideration of this point may help to reconcile apparently contradictory findings. Despite these difficulties, the fucoid zygotes are likely to continue to be an important experimental system. Technology, including the development of more specific inhibitory reagents, may allow some of the shortcomings of the system to be overcome, and careful consideration of experimental conditions may resolve some of the points of disagreement.

Selective grazing of the isopod Idotea baltica between Fucus evanescens and F. vesiculosus from Kiel Fjord (western Baltic)

Grazing rates of the isopod Idotea baltica on Fucus evanescens and F. vesiculosus (Phaeophyta) were quantified in laboratory feeding preference experiments. Fucus species were offered alone (no-choice) or simultaneously (choice). In three of four no-choice experiments and in all four choice experiments, I. baltica significantly preferred F. vesiculosus to F. evanescens. F. evanescens recently immigrated into Kiel Fjord and has increased in abundance since 1990. One possible reason for the competitive success of this species may be that, compared to F. vesiculosus, it is less preferred by I. baltica, the most abundant mesograzer at the study site.

Pyrolysis mass spectrometry: a fresh approach to old problems in brown algal systematics?

Pyrolysis mass spectrometry (PyMS) has been tested on five freeze-dried cultures of ectocarpoid algae and on live tissue from three field populations of Fucus species. The technique enabled discrimination of Baltic and Irish Sea isolates of Pilayella littoralis. The results were in agreement with the view that P. littoralis and Hincksia ovata may be considered members of a single family (Ectocarpaceae) and support the location of Elachista fucicola in the Elachistaceae. Microspongium globosum was least similar to the other isolates and, on present evidence, should be located in another higher taxon (Myrionemataceae?). Baltic F. vesiculosus could be distinguished from conspecific plants from the Irish Sea, but the technique failed to separate clearly Irish Sea F. serratus and F. vesiculosus. This anomalous result is considered a probable consequence of introgression occurring at a shore level where the two species coexist. It is concluded that PyMS has considerable potential in the study of brown algal systematics.

Quaternary marine macroalgae from Greenland

Four species of brown algae, Sphacelaria arctica, S. plumosa, Desmarestia aculeata, and midribs of a Fucus species have been found in Holocene and interstadial deposits in Greenland. The green alga Chlorochytrium dermatocolax and the red alga Audoui‐nella cfr. microscopica are reported for the first time in such deposits. All species are present in the extant flora of marine, benthic algae from Greenland. They are very well preserved and can be identified to species level.

Spatial distribution and quantification of Fucus species and Ascophyllum nodosum beds in intertidal zones using spot imagery

Spatial distribution and quantification of Fucus species and Ascophyllum nodosum beds in intertidal zones using spot imagery

The Recovery of Net Photosynthesis during Rehydration of Three Fucus Species from the Swedish West Coast Following Exposure to Air

Article The Recovery of Net Photosynthesis during Rehydration of Three Fucus Species from the Swedish West Coast Following Exposure to Air was published on January 1, 1992 in the journal Botanica Marina (volume 35, issue 6).