Nutrient availability and accumulation of phenolic compounds in the brown alga Fucus vesiculosus

Plant phenols tend to accumulate under conditions where plants have excess carbon above the level which can be used for growth, and where phenylalanine, the substrate of phenylpropanoid synthesis, accumulates due to suppressed protein synthesis. These internal balances imply an accumulation of phenols as a consequence of nitrogen deficiency suppressing plant primary metabolism. In three sublittoral populations of the brown alga Fucus vesiculosus (L.) collected from the northern Baltic Sea between May and September 1982, the accumulation of phenolic compounds correlated inversely with nitrogen content of thallus; higher phenolic contents were on average found under nitrogen deficiency. Phenolic content did not correlate with carbon content of thallus as such, while a significant negative correlation was found with the nitrogen: carbon ratio. Phenolic compounds, although having possibly defensive functions in plants, may thus partially vary as a function of resource availability rather than as a result of an active allocation into plant defences.     

Photosynthesis and ion loss in the brown algae Dictyopteris membranacea and Fucus virsoides

The sublittoral brown alga Dictyopteris membranacea (Stackhouse) Batters is very sensitive to low salinities. A one minute exposure to distilled water causes total breakdown of photosynthesis and respiration. The breakdown phenomena were studied as after-effects following re-exposure to sea water. Since rate of ion loss is highest during the first minute of osmotic stress, the irreversible metabolic depression appears to be due to fast ion loss. Photosynthesis of Fucus virsoides J.Ag is not affected by distilled water, even over very long periods of time.     

Feeding of the copepod Acartia tonsa on the diatom Nitzschia closterium and brown algae (Fucus vesiculosus) detritus

Integumental sensilla were examined in 39 species of meso- and bathypelagic shrimps and 6 species of epibenthic shrimps. A tuft organ, consisting of a group of openended, tubular setae and so probably functioning as a chemosensor, is described. A single tuft with ancillary smaller tufts occur on the dorsal median surface of the fourth abdominal segment and two pairs of tufts occur on the proximal dorsal region of the telson of all oplophorid and pandalid shrimps examined. An additional tuft is present on the fifth abdominal segment of the rare bathypelagic Physetocaris microphthalma Chace. No tuft organs were identified in Processa canaliculata Leach, suggesting that they may not occur in all families of caridean shrimps. Acanthephyrid, systellaspid and pandalid shrimps have the integument completely covered by scales. These are extremely delicate and are normally removed during the process of catching the shrimp through abrasion of the integument by the net. The scales are peculiarly orientated, pointing anteriorly in the anterior half and posteriorly in the posterior half of the body. They probably have a sensory function as distance receptors, monitoring water currents and disturbances in the environment surrounding the shrimp.     

Influence of environmental parameters on intraspecific variation in Fucus vesiculosus

The vesiculation and branching of Fucus vesiculosus L. were examined on plants from three different locations on the Maine Coast, USA. These localities varied in exposure to wave action and salinity. Statistical analysis of population differences was computed for 10 morphometric characteristics. It was found that decreased salinity correlated with increased vesiculation and branching. Increased wave action correlated with decreased vesiculation. Position within vertical range was not a factor in either vesiculation or branching.     

Fertilization in natural populations of the dioecious brown alga Fucus ceranoides and the importance of the polyspermy block

The brown alga Fucus ceranoides L. was studied in several estuaries on the Isle of Man (Great Britain) in the summers of 1989 and 1990. The objective were to determine the success of natural fertilization in a dioecious organism with external fertilization and to contribute to our understanding of processes such as polyspermy blocks and propagule settlement under natural conditions. Gamete release occurred on a semilunar cycle near full and new moons; at such times, settlement densities of 500 zygotes cm^-2 d^-1 were common. Gamete release was largely restricted to daytime high tides. Fertilization success was high: about 95 to 100% of all eggs released were fertilized, and 1 to 9% of these zygotes were polyspermic. The incidence of polyspermy increased towards the upper limit of F. ceranoides in the estuary of the river Neb; this may be significant in the context of the Na⁺-dependent block against polyspermy. Levels of polyspermy were not related to fertilization success (R²=0.06). Rates of pronuclear migration and karyogamy determined in the laboratory were used as an internal clock to estimate when eggs were fertilized in the field. Most eggs were fertilized 30 to 120 min after plants were immersed by the incoming tide, which corresponded to the period 60 min before to 30 min after high tide. The high success of fertilization suggests that polyspermy blocks are important in nature, and, in combination with the high settlement of zygotes, shows that population size in F. ceranoides is determined by post-settlement mortality, not by propagule availability.     

Determination of photosynthetic rates for the marine algae Fucus vesiculosus and Laminaria digitata

A continuously recording, flow-through oxygen electrode system for the measurement of oxygen exchange is described and applied to an investigation of photosynthetic rates in the marine algae Fucus vesiculosus L. and Laminaria digitata (Huds.) Lam. The photosynthetic rate (mg O₂.g dry weight^-1.h^-1) at 15°C and 21.5 mW.cm^-2 (usually just saturating) ranges in F. vesiculosus from 1.20 in basal portions of the thallus to 9.27 at the apices and in L. digitata from 1.19 mg O₂ at the thallus base to 3.97 mg O₂ at distances of several centimetres behind the upper thallus margin. This variation is reduced when the photosynthetic rate is expressed in terms of fresh weight or surface area.This research was carried out while one of us (R.J.K.) was an Alexander von Humboldt fellow at the University of Kiel, and is part of the programme Sonderforschungsbereich 95, Wechselwirkung Meer-Meeresboden, Universität Kiel.     

Seasonal variations in salt-march macroalgae photosynthesis. II. Fucus vesiculosus and Ulva lactuca

Photosynthesis in whole plants of the salt-marsh algae Fucus vesiculosus and Ulva lactuca was evaluated by ¹⁴C-uptake under a variety of light intensities at approximately mately monthly intervals during a 15-month study. Photosynthetic capacity in both species was closely related to seasonal irradiation patterns and changes in field biomass. Maximum photosynthesis occurred in the spring and summer months. Photosynthesis on a dry weight basis was higher in U. lactuca, while photosynthesis on a chlorophyll a basis was equal in both species. Photosynthetic capacity was inversely related to pigment content. Maximum chlorophyll a concentrations occurred during the winter. Frond profile studies in F. vesiculosus indicated that apices always exhibited greatest photosynthetic capacity. Uptake of ¹⁴C into ethanol-soluble and insoluble fractions was different in each species. F. vesiculosus showed greater activity in the ethanol-soluble fraction while U. lactuca exhibited greater activity in ethanol-insoluble fractions.This research was supported by Research Grant AG-375 from the National Science Foundation and, in part, by the State University of New York Research Foundation and the Energy Research and Development Administration (ERDA).     

Distribution and maximum growth depth of Fucus vesiculosus along the Gulf of Finland

 A survey of the distribution and maximum depth of a continuous Fucus vesiculosus belt was carried out in the Gulf of Finland in 1991. F. vesiculosus is widely distributed throughout the Gulf of Finland, including the vicinity of Vyborg Bay, Russia in the east. The maximum growth depth of F. vesiculosus in the Gulf of Finland reflects two different patterns according to the exposure to wave action. The most robust and continuous F. vesiculosus belt is observed on exposed shores, where the maximum growth depth is 5 to 6 m, with the optimum at 2 to 3 m. On moderately exposed shores the maximum growth depth is 3 m, with an optimum growth depth of <2 m. The maximum growth depth also varies geographically, with a decreasing trend towards the east. Maximum growth depth of F. vesiculosus correlates with light intensity. The compensation point for F. vesiculosus photosynthesis is about 25 μmol m⁻² s⁻¹, and photosynthesis is saturated at a light intensity of 300 μmol m⁻² s⁻¹. Vertical irradiance attenuation measurements in situ in summer revealed that for F. vesiculosus photosynthesis the quantity of light is optimal (200 to 300 μmol m⁻² s⁻¹) at <3 m depth. At depths >5 m the quantity of light is near or below the photosynthesis compensation point and insufficient for growth. These depth limits of light penetration coincide with measured growth depths of F. vesiculosus in the Gulf of Finland. Received: 7 May 1999 / Accepted: 18 November 1999     

Zonation,vesicle pressure and gas composition in Fucus vesiculosus and Ascophyllum nodosum at Kristineberg (West Coast of Sweden)

Features of fucoid zonation (Fucus spiralis, F. vesiculosus, Ascophyllum and F. serratus) in a vertical range of 60 cm at Kristineberg (Gullmar Fjord, W. Coast of Sweden) are described. In contrast to identical species occupying areas with wider tidal ranges, these plants are smaller in size and inhabit narrow, overlapping zones. Investigation into the magnitude of pressure and gas composition in vesicles of F. vesiculosus and Ascophyllum nodosum revealed an average positive pressure equivalent to 1.7 and 7 cm of water for the 2 plants in succession. These small values compare favourably with the pressure head to which such vesicles are subjected at Kristineberg. O₂-percentage amounts to 28.5% and 32.7% in vesicles of both plants in succession. O₂-values increase in daytime and decrease at night or when plants are maintained in the dark. CO₂-content in the two plants fluctuates between 0 to 2.6% and bears no correlation to the oxygen values. It is suggested that the pressure produced in the vesicles is due mainly to oxygen. Comparison of these results with those by other authors are made whenever possible.     

Photosynthesis and respiration in the alga Ahnfeltia plicata in a flow-through system

Photosynthesis and respiration in Ahnfeltia plicata (Huds.) Fries (Gigartinales) was measured in a seawater flowthrough system at different temperatures, salinities and photon flux densities (PFD). The exchanges of dissolved oxygen and inorganic carbon were continuously recorded with an oxygen probe and a pH electrode measuring variation in CO₂–HCO ₃ ^- equilibrium as pH changes. Highest apparent photosynthesis at moderate photon flux density (PFD 50 E m^-2 s^-1) was found at 15°C and 33 S. Photosynthesis was measured up to PFD 500 E m^-2 s^-1 and no light saturation was documented. In the present experimental set-up, with continuous supply of fresh seawater, the number of limiting factors during photosynthesis measurements is reduced.     

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.     

Effects of salinity and bromine on zygotes and embryos of Fucus vesiculosus from the Baltic Sea

Zygotes and young embryos derived from Fucus vesiculosus collected in the archipelgo of Stockholm in 1990, growing at a salinity of 6 to 7 S, were cultured under different salinity conditions and in media of different bromine concentrations. Optimum salinity was 10 to 12 S for germination (rhizoid initiation) while apical hair formation showed a broader tolerance curve with an optimum at 8 to 14 S. Bromine caused inhibition of early development of F. vesiculosus. At 6 salinity a 50% reduction in germination took place at 10.0 mM Br and at 1.25 mM Br only 4.7% of the embryos developed apical hairs, as compared to 32.7% in the control. Bromine toxicity decreased at higher salinities. The results indicate that F. vesiculosus in the Baltic Sea has diverged from its Atlantic progenitors and to some extent acclimated to low salinity. Still, the salinity in the normal environment of the tested population is lower than optimum, leading to a lower degree of germination of zygotes, a lower growth rate of young embryos and probably also a higher sensitivity to additional stress factors such as chemical pollution.     

Biofouling attractants from a brown marine alga Ecklonia cava

In recent years, industrial pollutants and the mountain forest fire ashes released into seawater cause damage to the marine environment, mainly it reduces the algal productivity in the inter tidal region. To get recover from the stress due to pollutants and to increase the growth and development of biofouling algae (benthic organisms), Ecklonia cava extract was investigated for its biofouling attracting efficiency. Bioactive guided fractions of E. cava extract derived from column chromatography were tested against spore attachment of a fouling alga, Ulva pertusa. Fraction B showed increased spore attachment rate with a maximum of 92 +/- 5%. This fraction was further analysed on HPLC, GC-Mass and NMR, deduced as pentadecanoic acid.     

Increased seawater temperature and light during early springs accelerate receptacle growth of Fucus vesiculosus in the northern Baltic proper

In many temperate estuarine areas, ongoing climatic changes are expected to lead to higher seawater temperatures, to increased inflow of freshwater and nutrients (due to increased rainfall) and to altered light conditions. During the last two decades, several winters have been unusually mild in southern Finland, and the subsequent springs have been early. This may have consequences for the seasonality of many species, including the bladder-wrack, Fucus vesiculosus, whose reproductive cycle may be especially sensitive. In the present study, F. vesiculosus receptacles from the field were weighed regularly during three warm (early) springs and compared with receptacles from three cold (late) springs. On average, the first sign of receptacle growth in the field occurred 5–6?weeks earlier and receptacles probably matured 2–3?weeks earlier during the warm springs than during the cold springs. This may be due to differences in seawater temperatures among years, but significantly heavier receptacles at 0.8?m compared to at 3.1?m further suggests the importance of light for receptacle growth as a measure of maturation, since there were no depth-related differences in seawater temperatures. Also, when plotting receptacle wet weights against seawater temperatures, the importance of light can be seen as different regression relationships (slopes and intercepts). In an outdoor aquarium experiment, the effects of temperature and light on receptacle growth were also tested, and there were significant differences between shallow and deep specimens, but temperature and light had no effects, except on initial receptacle growth. Since oogonian development, and thereby the time for zygote release, followed the receptacle growth curve, this could mean a mismatch between the timing of F. vesiculosus zygote settlement and the cover of competing filamentous algae, but such species interactions require further investigations in order to better understand their possible consequences.     

Juvenile life stages of the brown alga Fucus serratus L. are more sensitive to combined stress from high copper concentration and temperature than adults

The combined effects of exposure to copper and temperature were investigated in adult specimens and germlings of the canopy-forming brown alga Fucus serratus. A matrix of four temperatures, 6, 12, 17 and 22 °C, and three concentrations of copper, 0, 100 and 1,000 nM total copper were used. Measured endpoints were growth rate, chlorophyll fluorescence parameters and for germlings also survival. The growth rate of adult specimens of F. serratus changed with increasing temperature. Growth tended to be negatively affected by high concentrations of copper when exposed to heat (22 °C) though not significantly so. The photosynthetic performance (i.e., chlorophyll fluorescence parameters: F _v/F _m, maximum electron transport rate (ETR_max) and maximum non-photosynthetic quenching (NPQ_max) of adults was largely unaffected by both copper and temperature. Germling survival, growth rate and chlorophyll fluorescence parameters were affected by the combination of copper concentration and temperature. Increasing temperature led to reduced survival, increased rhizoid growth and higher F _v/F _m and ETR_max, whereas high copper concentration had a negative effect on the latter three endpoints. The negative effect of high copper concentration was amplified by high temperature. We conclude that juveniles of F. serratus are more susceptible to environmental stressors than adult specimens and recommend therefore including early life stages when assessing the risk of exposure to toxic compounds. Considering the response of adult specimens only may lead to false conclusions regarding the ecological impact of environmental stress.     

Demography of the intertidal brown alga Pelvetia fastigiata in Southern California,USA

The demography of Pelvetia fastigiata was studied from 1973 through 1977 in the intertidal zone near La Jolla, California, USA. Populations were usually small and relatively stable as new recruits replaced older individuals that were lost; however, in 1977 high recruitment substantially increased total abundances. The survivorship of recruits was similar regardless of the season or year of recruitment. Mortality rates decreased with age, and the mean life expectancy continued to increase for at least 1 yr. Losses of juveniles were high; 50% lived 80 d and only 9% survived to the age of first reproduction (about 1.5 yr). Plants present at the start of the study had higher survivorship rates than new recruits, 19 and 7%, respectively, living more than 3 yr. Individuals within aggregations of large plants lived longer than most dispersed individuals, and aggregations remained intact throughout the study in spite of low recruitment. Established individuals had low mortality rates and populations probably relied on these persistent individuals for reproduction.     

Adaptation of light-harvesting pigments to downwelling light and the consequent photosynthetic performance of the eulittoral rockweeds Ascophyllum nodosum and Fucus vesiculosus

We compared the effect of habitat and water depth on the light-harvesting pigment content for Ascophyllum nodosum and Fucus vesiculosus at two near-shore stations in Long Island Sound (USA). Excised pieces of seaweeds were attached at depth intervals to a vertically buoyed line, and left in situ for 7 days. For comparison, fronds were collected from sun and shade habitats in the littoral zone. The three major antenna (light-harvesting) pigments increased in concentration with depth or shade. Chlorophyll c to a ratios remained stable at about 0.2. Fucoxanthin to chlorophyll a ratios decreased by 20 to 30% with depth or shade. Although pigment composition for the two rockweed species was equivalent, the maximum photosynthetic performance of F. vesiculosus exceeded that of A. nodosum by a factor of 2, while the compensation depths for 4 m-adapted A. nodosum and F. vesiculosus under natural limiting light conditions were equivalent. Plants held at 4 m had higher photosynthetic rates compared with plants held at 0 m, no matter the depth of measurement. Indirect evidence indicates that the enhanced photosynthesis of 4 m-adapted plants is due not only to higher concentrations of antenna pigments but to other physiological factors as well. We conclude that the clearly delineated vertical distribution of these two canopy species, the F. vesiculosus zone over the A. nodosum zone, is not determined by light quantity or quality, but by biotic factors as evidenced by the experiments of Menge which are cited herein.     

Photosynthesis and amelioration of desiccation in the intertidal saccate alga Colpomenia peregrina

Rates of gross photosynthesis for the intertidal saccate alga Colpomenia peregrina (Sauv.) Hamel were determined under submersed and emersed conditions. Maximal photosynthetic rates were lower than for most seaweeds but comparable with other saccate members of the genus. By fitting the data to a hyperbolic tangent function, maximal photosynthetic rates were estimated to be 5.29 mmol CO₂ m^-2 h^-1 under submersed conditions and 2.06 mmol CO₂ m^-2 h^-1 under emersed conditions. I_k for submersed thalli was 69.1 E m^-2 s^-1, wherea for emersed thalli it was 149.0 E m^-2 s^-1, or 2.2 times higher. At low tide in the field and under saturating irradiance, carbon from seawater retained within the thallus cavity was assimilated at 0.9 mmol CO₂ m^-2 h^-1. In the laboratory under emersed conditions, carbon from this source was taken up at 0.6 mmol CO₂ m^-2 h^-1 at 20°C and at 0.34 mmol CO₂ m^-2 h^-1. Retained seawater also greatly reduced drying under desiccating conditions. Experimental thalli from which seawater had been removed lost thallus water continuously throughout the drying period (120 min). On the other hand, control, thalli lost water for the first 15 min, after which no further water loss occurred. At the termination of the experiment, control thalli had lost 7.2% of their water, whereas experimental thalli had lost 39.2%. Desiccation affected the emersed photosynthetic rate of experimental and control thalli. Emersed photosynthetic rates for thalli dried for 15 min were higher than for fullyhydrated thalli. However, emersed photosynthesis of thalli dried for longer than 15 min was lower than fully-hydrated rates and was directly related to percent water loss. Utilizing data from this study, a model was constructed to determine total photosynthetic production of C. peregrina over a single daylight period. From these calculations it was determined that emersed photosynthesis can increase daily photosynthetic production of C. peregrina by 50%.     

Occurrence and significance of nitrogen transport in the brown alga Laminaria digitata

Nitrogen transport in a Laminaria digitata (Huds.) Lamour population growing at Arbroath, Scotland has been investigated (during the period 3 June 1981 to 3 July 1981), using ¹⁵N as tracer. NO ₃ ^- was assimilated both by the blade meristem and by the mature blade. NO ₃ ^- uptake by the blade meristem alone was insufficient to supply the nitrogen demand for growth. This additional demand was met by nitrogen transport from the mature blade to the meristem. It was estimated that 70% of the nitrogen demand of the meristematic region was supplied by nitrogen transport from the mature blade. Although transport occurred, the size of the endogenous pool of stored nitrogen in the mature blade did not change, the quantity of nitrogen transported being equivalent to the amount of NO ₃ ^- assimilated during the experimental period. The possible co-transport of nitrogen and carbon is discussed.