Quantitative studies on brown algal phenols. I. Estimation of absolute polyphenol content of Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.)

Methods for estimating the absolute polyphenol content of the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.) have been developed and tested. Polyphenols were extracted almost quantitatively from Ascophyllum nodosum using aqueous acetone, whereas this procedure was somewhat less efficient with Fucus vesiculosus. Colorimetric methods based on the Folin-Denis reagent, Brentamine Fast Red 2G Salt, and vanillin-H₂SO₄ were applied to acetone-free extracts for determination of polyphenol content relative to suitable reference compounds. Gravimetric methods based on hide powder and on haemoglobin were employed to derive ‘estimation factors’ (EFs) which allow calculation of the absolute polyphenol content from the relative polyphenol content. The values calculated for absolute polyphenol content are considered to be reasonably accurate, despite imprecisions in the methods and despite often large standard deviations, and re-emphasize the potential physiological and ecological significance of brown algal polyphenols. Although the precise EFs calculated here are not valid for other brown algae, the methods are considered to be generally applicable to other Phaeophyceae.     

Quantitative studies on brown algal phenols IV. Ultraviolet spectrophotometry of extracted polyphenols and implications for measuring dissolved organic matter in sea water

Poor correlation exists between levels of total phenols and of ultraviolet-absorbing materials in extracts of the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus L. The uv extinction sp coefficient of a major exuded polyphenol fraction increases rapidly and markedly in sea-water solution. Consequently, uv spectrophotometry cannot provide a useful measure of either total polyphenols or total organic matter in extracts or exudates from these brown algae. Moreover, considerable errors may be introduced when uv spectrophotometry is used to estimate dissolved organic matter in sea water which receives significant exudation from brown macrophytes.     

Natural chelators in sea water: Detoxification of Zn2+ by brown algal polyphenols

We have examined growth responses of several species of marine phytoplankton, cultured with and without heavy metal stress, to supplements of polymeric polyphenols from the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus L. In the absence of additional heavy metals. supplements of up to 4000 μg. 1 of polyphenols had a small effect on initial growth rates for three of these microalgae and had no effect on maximum cell densities for four species. One very common, heavy metal-sensitive diatom, Skeletonema costatum (Grev.) Cl., showed significantly increasing maximum cell density in the cultures, with increasing addition of polyphenols to the medium. The toxicity of Zn²⁺ (0.5–2.0 mg·1 ¹) to cultures of the diatom Phaeodactylum tricornutum Bohlin was relieved by supplements (100–200 μg·1 ¹) of the brown algal polyphenols. Exudation of these polyphenols from brown seaweeds may contribute to the natural chelating capacity of inshore sea water.     

Biostimulant activity of brown seaweed species from Strangford Lough: compositional analyses of polysaccharides and bioassay of extracts using mung bean (Vigno mungo L.) and pak choi (Brassica rapa chinensis L.)

The aims of this study were to characterise the composition of seaweed species and to evaluate the efficacy of aqueous extracts as plant biostimulants. Five species (Ascophyllum nodosum, Fucus serratus, Fucus vesiculosus, Laminaria hyperborea and Sargassum muticum) of seaweed were harvested from Strangford Lough, Northern Ireland for the evaluation of polysaccharides, indole-3-acetic acid (IAA), carbon, nitrogen, lipid, ash and mineral contents. The compositional analyses of the five species and their freeze-dried extracts were also carried out using thermogravimetric analysis, scanning electron microscopy and X-ray microanalysis. The concentration of IAA in the acid extracts of the five species ranged between 2.74 and 46.8?ng?g^?1. The carbon, nitrogen, lipid and ash contents ranged between 25.0 and 38.6, 1.37%, and 3.16, 0.83%, and 3.98 and 18.10 and 47.68%, respectively. L. hyperborea and S. muticum contained the highest amounts of minerals. The biostimulant activities of acidic (pH?3.0), neutral (pH?6.5) and alkaline (pH?9.0) extracts were determined by mung bean bioassay. The alkaline extracts from F. vesiculosus and A. nodosum stimulated significantly (P?<?0.001) higher dry matter (DM, %) yield of the mung bean plants. The majority of the acidic extracts significantly (P?<?0.001) enhanced root formation on the mung bean stem cuttings compared to alkaline or neutral extracts. The acidic extracts of the five species, water control and a commercial product were evaluated as foliar feeds for pak choi plants using a hydroponic production system. The interaction of species, e.g. A. nodosum and F. vesiculosus and the two treatment dilutions on DM yield increases of pak choi were significant (P?<?0.05).     

Adaptations by macroalgae to low carbon availability. I. A buffer system in Ascophyllum nodosum, associated with photosynthesis

Abstract The exchange of CO₂, H⁺ and O₂ between seawater and the intertidal brown macroalga Ascophyllum nodosum (L.) Le Jolis were measured in a flowthrough system. While the algae were kept in darkness, seawater with artificially increased alkalinity and pH at 9.85, was alternated with ‘normal’ seawater at pH 8.0. A proton buffering system, with capacity to release and reabsorb about 20 μmol protons per gram alga (fresh weight) was revealed. As the algae were returned to the ‘normal’ seawater, the kinetics of proton reabsorbtion indicated that a proton uptake was gradually induced. This proton uptake, which was not connected to ion exchange in the cell wall, reached its maximum after 12 h. If subjected to high alkalinity seawater in the light, A. Nodosum for a certain period of time was capable of carrying out O, evolution in excess of the import of inorganic carbon. This ‘photosynthetic buffering capacity’ amounted to about 17 μmol O; per gram alga. Besides depending on a buffer of photorcducible substances, this ‘photosynthetic buffering capacity’ appeared to be functionally connected with the proton buffer. The time course for the discharge of the ‘photosynthetic buffer system’ and for the reabsorbtion of protons into the proton buffer (about 6h for 90× of the capacity at a temperature of 6°C) suggests that the ‘photosynthetic buffer system’ has a functional importance in the adaptation of A. nodosum to intertidal regions. The function of the buffer system is discussed in relation to the crassulacean acid metabolism (CAM)-like characteristics recently shown for the intertidal brown algal family Fucaceae.     

Oligomeric polyphloroglucinols from Fucus vesiculosus: Photoplate mass spectrometric investigation

Fucus vesiculosus accumulates polyphenols consisting of four-seven phloroglucinol units. These ‘oligomers’ are primarily ether-linked; no evidence could be found for entirely phenyl-linked ‘oligomers’ having more than four phloroglucinol units, nor for any ‘oligomer’ with more than three phenyl linkages, nor for vicinally trihydroxylated polyphloroglucinols.     

Lipid Metabolism in the Brown Marine Algae Fucus vesiculosus and Ascophyllum nodosum

Lipid metabolism and environmental effects on this process havebeen studied in the marine brown algae Fucus vesiculosus andAscophyllum nodosum. These algae showed very similar patternsof lipid metabolism during 24 h incubations. Labelling from[1-¹⁴C]acetate showed the major labelled lipids to be the ß-alanineether lipid and the neutral lipid fraction in both algae. Ofthe glycolipids, only sulphoquinovosyldiacylglycerol was welllabelled and the phosphoglycerides were all poorly labelled.The major labelled fatty acids were palmitate and oleate, againin both algae, although Fucus vesiculosus also showed significantlabelling of stearate and behenate. Although the amount of fattyacid labelling increased with time, the proportion of labelin palmitate and oleate remained approximately constant. Verylong chain fatty acids (arachidic, behenic) were increasinglylabelled with time. Lowered incubation temperatures decreased labelling of the saturatedfatty acids. Cu²⁺ increased the proportion of oleate labelledin both algae, and of linoleate in Fucus vesiculosus. This cationdecreased the percentage labelling of stearate and myristatein Ascophyllum nodosum. Lipid metabolism in Ascophyllum nodosumwas more sensitive to raised Cu²⁺ levels than in Fucus vesiculosus Key words: Acyl lipid metabolism, Fucus vesiculosus, temperature effects, Ascophyllum nodosum, copper pollution     

Production of fucoid brown algae <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis> and <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> in the White Sea

Year-round studies of photosynthesis and respiration in the fucoid brown algae Ascophyllum nodosum and Fucus vesiculosus in the White Sea were performed. The annual specific production of the macrophytes was determined to be 1314 and 1642 cal/g of wet weight for A. nodosum and F. vesiculosus, respectively. The total annual production of fucoids (4.88 × 10¹¹ kcal) comprised about 0.8% of the phytoplankton production in the White Sea.     

SETTLEMENT AND SURVIVAL OF POLYSIPHONIA LANOSA (CERAMIALES) SPORES ON ASCOPHYLLUM NODOSUM AND FUCUS VESICULOSUS (FUCALES)1

The settlement patterns of spores of Polysiphonia lanosa (L.) Tandy on Ascophyllum nodosum (L.) Le Jolis and Fucus vesiculosus L. were studied using a flow tank. Settlement sites were defined as ‘sheltered’ or ‘exposed.’ Surface area calculations revealed non-random settlement on A. nodosum, with higher than expected spore frequencies on the thallus and lateral pits and lower than expected frequencies on the vesicles. Settlement of F. vesiculosus was random and significantly lower than on A. nodosum. On the shore, survival of sporelings from September (post-sporulation) to May (pre-sporulation) was highly non-random on both basiphytes. On A. nodosum, lateral pits ('sheltered') showed the highest survival frequency. Here the proportion of surviving sporelings increased over the study period, whereas the proportion on open thallus area ('exposed') decreased. On F. vesiculosus also preferential survival occurred on ‘sheltered’ sites such as vesicle/thallus interfaces and wounds. Between September and May, all P. lanosa sporelings were lost from ‘exposed’ areas (thallus surface and vesicles). Overall, frequencies of surviving sporelings were much greater on A. nodosum than on F. vesiculosus. These results are discussed with reference to basiphyte morphology, epiphyte removal mechanisms and the survival stratagy of P. lanosa.     

Occurrence of steryl glycosides and acylated steryl glycosides in some marine algae

There is some controversy concerning the presence of steryl glycosides and acylated steryl glycosides in eucaryotic algae. These two classes of sterol compounds were investigated in species belonging to the three major groups of eucaryotic algae: green algae (Ulva gigantea, Cladophora rupestris), brown algae (Fucus vesiculosus, Ascophyllum nodosum), and red algae (Rhodymenia palmata, Porphyridium sp.). All these algae contain both steryl glycosides and acylated steryl glycosides. The sterol components of these compounds vary according to the alga but they are always the same as the free sterols of the alga in question. The most common sugar moiety is glucose. In the acylated steryl glycosides, the fatty acid is mainly palmitic acid. The percentage of these compounds (as a percentage of the total sterol content) is often low.     

Fucose-containing polysaccharides in the brown algae Ascophyllum nodosum and Fucus vesiculosus

The fucose-containing, sulfated polysaccharides from Ascophyllum nodosum and Fucus vesiculosus were isolated by extraction with water adjusted to pH 2. Pure fractions were carefully separated by fractional precipitation with ethanol from aqueous solutions containing magnesium or calcium chloride. Progress in the fractionation efforts and purity of the fractions isolated were established by free-boundary and cellulose acetate clectrophoresis. Ascophyllan, two “complexes”, and a galactofucan were isolated from A. nodosum. An ascophyllan-like fraction, and a “complex” were isolated from F. vesiculosus. Mild, acid hydrolysis (0.02m hydrochloric acid, 1 h, 80°) converted each of the “complexes” into an electrophoretically faster-moving and a slower-moving component. The “complex” from F. vesiculosus comprised a greater proportion of the extract than did the two “complexes” from A. nodosum. In addition, the Fucus “complex” was richer in fucose*. However, the data suggest that neither species contains a pure fucan sulfate in the native state.     

Electron microscopy of human erythrocytes agglutinated by lectin from Codium fragile ssp. tomentosoides and pseudo-haemagglutinin from Ascophyllum nodosum

Human erythrocytes were exposed to extracts of Codium fragile ssp. tomentosoides, Ascophyllum nodosum, Dolichos biflorus seeds and a solution of purified polyphenols from Ascophyllum nodosum. In each case the erythrocytes appeared to agglutinate. Agglutinates were examined by scanning electron microscopy. Photomicrographs of the erythrocytes exposed to lectin-containing extracts of C. fragile and D. biflorus showed the typical appearance of agglutinated cells. Photomicrographs of the erythrocytes exposed to the crude extract and purified polyphenols from A. nodosum were similar to each other, but quite different in appearance to erythrocytes agglutinated by the lectins from C. fragile and D. biflorus. This evidence adds further support to the contention that lectin presence recorded in brown algal extracts is largely due to ‘pseudoagglutination’ produced by polyphenols contained in these extracts.     

Rates of oxygen consumption by Thais (Nucella) Lapillus (L.)

Oxygen consumption by Thais varied seasonally with higher values in summer than in winter. This seasonal difference was due in part to the effects of temperature and in part to those of feeding. During feeding, rates of oxygen consumption were high, but declined in the period between meals. There was little evidence of acclimation of oxygen consumption to changes in temperature; low (winter) rates of consumption were more sensitive to increases in temperature than were high (summer) rates. A polynomial expression, including terms for temperature and ‘time since last meal’, was derived for the constant a′ in the allometric equation relating oxygen consumption (_o2) to dry body weight: _o2 = a′.W^0.511.     

Interactions of Patella and macroalgae with settling Semibalanus balanoides (L.)

Biological interactions affecting densities of settling and newly-settled Semibalanus balanoides (L.) have been investigated by manipulative field experiments on the Isle of Man.The effects of sweeping by fucoid clumps of different species and Patella browsing have been compared on moderately-exposed shores. Patella allowed barnacle settlement by preventing growth of competing green algae, but reduced post-settlement densities. Small clumps of Fucus spiralis L., F. vesiculosus L, and F. serratus L. all reduced settlement considerably more so than limpets. F. serratus had the greatest sweeping effect.Interactions between macroalgae and Semibalanus balanoides have been investigated at all levels on sheltered shores and low down on more exposed shores. In the Fucus spiralis and F. vesiculosus zones, post-settlement numbers were higher than in adjacent areas where the canopy was removed. Barnacles did not settle readily in the Ascophyllum zone in either experimental or control areas. Settlement occurred in the upper part of the Fucus serratus zone in experimental areas where the canopy was removed but not in control areas. No settlement occurred in either treatment or control areas lower in the F. serratus zone. At all levels on the shore fucoid canopies seemed to reduce cyprid settlement, but the effect was greatest amongst F. serratus where there was total prevention. High on the shore the effect of enhanced post-settlement survival under the canopy outweighs reduction of cyprid settlement thus there are greater numbers in the controls. Competition with red algal turfs was shown to set the lower limit of the barnacle zone on a vertical pier face.     

Substratum selection and egg-capsule deposition in Nassarius reticulatus (L.)

When offered a range of 14 pairs of different substrata consisting of five brown algae, five red algae, three bivalve shells, and sandstone pebbles, spawning Nassarius reticulatus (L.) selected only four species of red algae on which to deposit egg capsules. There was some evidence of a greater preference for the red alga Gigartina stellata (Stackhouse). When offered a choice between only Gigartina and another red weed, Polyides rotundus (Hudson), there was a highly significant preference for the former. Some reasons for the selectivity are suggested and discussed.     

The effect of copper on length increase in Ascophyllum nodosum (L.) Le Jolis

The increase in length of Ascophyllum nodosum (L.) Le Jolis was measured in copper concentrations varying from 14–5000 μg/1 sea water. The growth was unaffected by concentrations of 33 μg/1 or less added for a period of 11 days, but at higher concentrations growth was gradually reduced. When the number of days (x) of exposure to a concentration (y) (y > 33 μg/1) is compared with z (the corresponding percentage reduction of growth rate), the data fit the equation z = 0.084 xy up to at least z = 60%.     

Effects of filamentous algae and deposited matter on the survival of Fucus vesiculosus L. germlings in the Baltic Sea

As a result of increased nutrient levels in the Baltic Sea during thepast 50 years, mass developments of filamentous algae have become a commonfeature along the Swedish east coast and deposition of organic matter has alsoincreased. To test whether these two factors have any effects on the early lifestages of Fucus vesiculosus a number of laboratory andfield studies were conducted. The amount of epilithic and epiphytic filamentousalgae on F. vesiculosus and the amount of deposited matterin the littoral zone were quantified during the two reproductive periods ofF. vesiculosus, early summer (May–June) and lateautumn (September–October). Both filamentous algae (Cladophoraglomerata) and deposited matter (introduced either before or aftersettlement of fertilized eggs) were shown to significantly decrease the numberof surviving germlings. The survival of germlings seeded on stones withfilamentous algae, or seeded on culture dishes concurrently with the lowestconcentration of deposited matter (0.1 g dm^–2),was 5% or less. In the field, the amount of filamentous algae was significantlyhigher during F. vesiculosus summer reproduction, whereasthe amount of deposited matter collected in traps was significantly higherduring the period of autumn reproduction. The greatest biomass of filamentousalgae was observed at sheltered sites. Based on the negative effects offilamentous algae and deposited matter on Fucusrecruitmentand the observation of local and seasonal differences in abundance offilamentous algae and deposition, we suggest that the prerequisites for thesurvival of either summer or autumn-reproducing populations of F.vesiculosus in the Baltic Sea may differ locally.     

Influence of phytohormones on morphology and chlorophyll a fluorescence parameters in embryos of Fucus vesiculosus L. (Phaeophyceae)

While a variety of plant hormones from brown algae were described, there were few studies that examined the combined effects of these hormones on morphogenesis and photosynthetic physiology in developing fucoid embryos. We evaluated the effects of phytohormones to determine the extent, to which responses were similar to those of terrestrial plants. Kinetin, IAA, ABA, GA₃, and kinetin + IAA were added to seawater at a physiological concentration (1 mg/L), and embryos of Fucus vesiculosus L. were grown for 10 days. Photosynthetic activity of single embryos or embryo cells were characterized using the following fluorescence parameters: minimum fluorescence yield (F ₀), maximum quantum yield (F _v/F _m), relative maximum rate of electron transfer to photosystem II under saturation irradiances (rETR_max), photosynthetic efficiency under non-saturating irradiances (αETR) and saturation irradiance (E _k). In addition, embryo length and diameter and apical hair length and number were determined. Morphological changes associated with hormone treatments included an increase in the embryo length in the presence of IAA, an increase in the embryo diameter in the presence of IAA, kinetin, and kinetin + IAA, an increase in the maximum hair length and number in the presence of kinetin + IAA, and a decrease in the hair length and number in the presence of ABA. With respect to fluorescence parameters, significant effects of phytohormones included an increase in the F ₀ and F _v/F _m at kinetin treatment, a synergistic effect of kinetin + IAA on F _v/F _m, rETR_max, and αETR, a promotion of F _v/F _m by GA, and a decrease of the parameters by ABA. These results are consistent with the data on responses of land plants to the same hormones and suggest that brown algae have evolved regulatory mechanisms for morphogenesis and photosynthetic regulation similar to plants.     

Polar extracts of the brown alga Fucus vesiculosus (L.) reduce assimilation efficiency but do not deter the herbivorous isopod Idotea baltica (Pallas)

Plant secondary metabolites provide resistance against herbivory if they are capable of decreasing herbivore performance or deterring feeding. Here we test the effects of phlorotannin-containing polar extracts from the brown alga Fucus vesiculosus on the assimilation efficiency and feeding preferences of the herbivorous isopod Idotea baltica. We test the effects separately for each sex of the isopod to test the hypothesis that the digestive efficiencies of the sexes may have diverged. Phlorotannin-containing polar extracts were incorporated into an agar-based artificial food in varying amounts. We also varied the quality of the food, using high-quality food containing animal proteins and low-quality food containing only algal material. The total assimilation efficiency as well as the assimilation efficiencies of carbon and nitrogen decreased with an increasing concentration of phlorotannin-containing extracts. The negative effects on carbon and nitrogen assimilation were higher when extracts were incorporated in the high-quality food. Females were consistently more efficient than males in all assimilation measures; there were no interactions between sex and food quality or phlorotannin concentration, suggesting that the digestive efficiency of the sexes had diverged but that the two sexes responded similarly to phlorotannin enriched artificial food. Although phlorotannin-containing extracts were harmful to performance, they did not deter feeding in preference tests. On the contrary: the isopods preferred the food containing more phlorotannins, suggesting that phlorotannins may act as cues in host recognition. Thus phlorotannins were inefficient deterrents, and I. baltica seems to be adapted to utilizing phlorotannin-containing foods despite their detrimental effects on assimilation. We suggest that F. vesiculosus provides a predation refuge and temporal constancy in availability for I. baltica, both of which select for the ability to utilize it as a food. Phlorotannin-containing polar extracts from F. vesiculosus are still harmful digestibility reducers, and may thereby prevent complete specialization and generate selection for utilization of a wider host range.     

Tritrophic Interactions of Cowpea [Vigna unguiculata subsp unguiculata(L.)], Aphids [Aphis craccivora (Koch)] and Coccinellids [Menochilus sexmaculatus (Fab.)] under eCO2 and eTemp

Experiments were conducted to understand the direct and indirect effects of temperature and elevated CO₂ (eCO₂), on tritrophic interactions of cowpea (Vigna unguiculata subsp. unguiculata L.), legume aphid Aphis craccivora Koch and coccinellid predator Menochilus sexmaculatus Fab. Reduction of the leaf nitrogen (6%), amino acid (6%) and protein (7%) of cowpea foliage with increased carbon (13%) and C:N ratio (21%) at eCO₂ over aCO₂ indicated the dilution of biochemical constituents at first trophic level. Shortened development time, DT and increment of reproductive rate, RR at eCO₂ over ambient CO₂(aCO₂)was significant with increase in temperature from 20 to 35?°C. Reduction of the mean degree day, DD requirement of both nymphal (75.79?±?15.163) and adult stages (157.15?±?67.04) at eCO₂ over aCO₂ and same was reflected in the summation DD for both the stages at eCO₂ (232.96?±?80.32)and aCO₂ (247.07?±?64.77) across six temperatures. The ‘r_m’ and ‘R_o’ increased gradually with increase in temperature followed the non-linear trend and reached maximum values at 27?°C with shortened ‘T’ across 20 to 35?°C temperatures at eCO₂ indicating the significant variation of growth and development at the second trophic level. Decreased grub duration (23%) with increased predation capacity (19%) of M. sexmaculatus on A. craccivora at eCO₂ over ambient was noted, indicating the incidence of A. craccivora is likely to be higher with increased predation in the future climate change scenario.