Sargassum Siliquosum Research Articles

Nitrogen excretion by the lobsters Panulirus ornatus and Thenus australiensis and uptake by the brown algae Sargassum siliquosum: Implications for integrated recirculated aquaculture systems

Farming extractive species such as macroalgae that take up nitrogen (N), with fed species (e.g., lobsters, finfish, prawns) is termed integrated multi-trophic aquaculture (IMTA). In recirculating aquaculture systems (RAS), high concentrations of nitrogenous waste can become toxic to the fed species and macroalgae offers a method of mitigating N waste. To utilise macroalgae as a biofilter for N waste, an understanding of their N ecophysiology of both the fed and extractive species is needed. In this study we first determine the ammonium and urea excretion rates for emerging aquaculture candidates the tropical rock lobsters, Panulirus ornatus (TRL) and slipper lobster, Thenus australiensis (SL). Using multiple flask uptake experiments, we then determined the N ecophysiology of the tropical brown macroalga, Sargassum siliquosum, to assess its potential use as a biofilter in a lobster RAS. Routine (basal) N excretion was predominantly ammonium with only a minor contribution of urea (8 and 13% for TRL and SL respectively). For both lobster species, ammonium and urea excretion substantially increased post-prandial, peaking at levels 3.6 times greater than basal amounts for TRL and 3.2 times greater for SL, and remained elevated for between 32 and 38 h. Uptake of both ammonium and nitrate by S. siliquosum showed saturating kinetics, where the kinetic parameter Vmax is the maximum rate of uptake, Ks is the half-saturation constant and the Vmax:Ks-ratio is a proxy for the algae's affinity of uptake for that respective nutrient: for ammonium Vmax = 110.9 μmoles g−1 dry weight (DW) h−1 and Ks = 37.9 μM and for nitrate Vmax = 152.7 μmoles g−1 DW h−1 and Ks = 58.52 μM. Urea uptake was highly variable with both positive and negative (i.e. urea release from tissue) rates recorded; when positive values were considered, Vmax = 55.5 μmoles g−1 DW h−1 and Ks = 17.65 μM. We used uptake and excretion rates from our study to derive a unit mass stocking ratio of algae to lobster (algae: animal) to offset N pollution in RAS. The ratios of TRL to algae to offset NH4+ and urea post-prandial were 5.15E-04 and 3.09E-04 respectively and for SL, 4.46E-04 and 6.31E-04 respectively. The findings serve as a reference for future studies on integrating Sargassum species into RAS and IMTA systems.

Plantlets directly developed from secondary phyllodes of Sargassum siliquosum J. Agardh: Implication for seedling production during the off-reproductive season

Development of plantlets was observed from excised secondary phyllodes of Sargassum siliquosum within a two-week period under culture conditions of 20 °C ambient temperature, 26 °C seawater temperature, 200 μmol photons m−2 s−1 light intensity, 12:12 L:D photoperiod, pH 8, and 35 psu salinity. The plantlets developed along the entire margin and both surfaces of the phyllode. Initially, small protuberances of 57.0–76.21 μm diameter were observed to develop on the surfaces that ultimately developed into plantlets with rhizoids however, no protuberances were observed along the margin of the phyllodes. These plantlets were separately cultured under similar environmental conditions except at 40 μmol photons m−2 s−1 light intensity on different substrata viz. clay panels, sponge, and cotton-mixed nylon. Among these substrata, the maximum attachment of plantlets was observed on sponge substrate followed by clay panels, and least on cotton-mixed nylon. Approximately 1427 plantlets developed on a single phyllode. These plantlets could be used as a source of planting materials during the off-reproductive season of Sargassum.

Effect of molecular mass and sulfate content of fucoidan from Sargassum siliquosum on antioxidant, anti-lipogenesis, and anti-inflammatory activity

Macroalgae (seaweeds) are abundant in functional polysaccharides known for their unique biochemical activities. In this study, the antioxidant, anti-lipogenic, and anti-inflammatory activities of the fucoidan extracted from brown seaweed Sargassum siliquosum were investigated by 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging ability, lipid synthesis inhibition, and suppression of pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) production, respectively. To examine the effect of molecular mass on fucoidan's bioactivities above, the extracted fucoidan was subject to hydrogen peroxide-mediated partial hydrolysis to obtain lower molecular mass compounds within the range of 107.3-3.2kDa. Results indicated that fucoidan's antioxidant activity increased with a corresponding decrease in molecular mass; the dosage for the half-maximal response (EC50) dropped from 2.58 to 1.82mg/mL when the molecular mass decreased from 107.3 to 3.2kDa. In addition, both the anti-lipogenesis and anti-inflammatory activities of fucoidan were significantly enhanced by 71.1% and 36.7%, respectively, when the molecular mass decreased to about 3kDa. To further test the effect of sulfation on fucoidan's bioactivities, low molecular mass fucoidan was treated with SO3-DMF to increase the sulfate content. The results indicated that when sulfate content increased from 18.7% to 32.1%, EC50 of DPPH decreased from 1.82mg/mL to 0.86mg/mL and the anti-inflammatory activity also increased by 35.2%; however, the anti-lipogenesis activity decreased.

Brown Seaweed Sargassum siliquosum as an Intervention for Diet-Induced Obesity in Male Wistar Rats.

The therapeutic potential of Sargassum siliquosum grown in Australian tropical waters was tested in a rat model of metabolic syndrome. Forty-eight male Wistar rats were divided into four groups of 12 rats and each group was fed a different diet for 16 weeks: corn starch diet (C); high-carbohydrate, high-fat diet (H) containing fructose, sucrose, saturated and trans fats; and C or H diets with 5% S. siliquosum mixed into the food from weeks 9 to 16 (CS and HS). Obesity, hypertension, dyslipidaemia, impaired glucose tolerance, fatty liver and left ventricular fibrosis developed in H rats. In HS rats, S. siliquosum decreased body weight (H, 547 ± 14; HS, 490 ± 16 g), fat mass (H, 248 ± 27; HS, 193 ± 19 g), abdominal fat deposition and liver fat vacuole size but did not reverse cardiovascular and liver effects. H rats showed marked changes in gut microbiota compared to C rats, while S. siliquosum supplementation increased gut microbiota belonging to the family Muribaculaceae. This selective increase in gut microbiota likely complements the prebiotic actions of the alginates. Thus, S. siliquosum may be a useful dietary additive to decrease abdominal and liver fat deposition.

Structure and Biological Activity Analysis of Fucoidan Isolated from Sargassum siliquosum.

Fucoidans are heterologous polysaccharides commonly seen in brown macroalgae and are known for their biological activity including anticancer, antiangiogenic, immunomodulation, and antiviral properties. The brown macroalga Sargassum siliquosum was used for the extraction and analysis of fucoidan in this study. The S. siliquosum fucoidan was indicated as a galactofucoidan composed of sugars, uronate, and sulfate at a ratio of 12:1:4 and its purity was 85% based on the abovementioned three major components. Structural analysis by electrospray ionization collision-induced dissociation tandem mass spectroscopy revealed that the purified fucoidan consisted of a carbohydrate chain composed of (1→3)-linked or (1→4)-linked l-fucose residues, with sulfate groups at C-2 and C-4 positions. Galactose residues with (1→4)-linkages function as the branch points and they are located at the C-3 or C-4 position of fucose residues. Galactose residues are sulfated mainly at C-4 and C-6, while some sulfation can also be seen at C-2. The fucoidan purified from S. siliquosum demonstrated antioxidant, anti-inflammatory, and antilipogenic activities.

Isolation and purification of brown algae fucoidan from Sargassum siliquosum and the analysis of anti-lipogenesis activity

Fucoidans are sulfated polysaccharides of marine origin and they have distinguished biological applications due to their anti-viral, anti-inflammatory, anti-angiogenic, and anti-tumorigenic potential. In this study, fucoidan was extracted from a brown macroalga (Sargassum siliquosum) using microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE). MAE under the condition of 750 W, 10 min, and a liquid/solid ratio of 15 mL/g, showed higher extraction efficiency with a total sugar yield of 6.94% per dry weight. The crude fucoidan obtained with ethanol precipitation was further purified by isoelectric point precipitation and calcium chloride addition (for protein and uronic acid removal), followed by anion-exchange chromatography (AEC) and dialysis. The purity of the polysaccharides content of crude fucoidan increased from 33.3–64.5% with a total sugar recovery of 50.3%. Based on the sugar and sulfate group (the major components of fucoidan), the purity of the final sulfated polysaccharides product is nearly 84.0%, and this purified fucoidan product was found to display biological activities linked to anti-lipogenesis with 28.9% decreased lipid synthesis in contrast to the free-fatty-acid-induced control.

Culture of the brown seaweed Sargassum siliquosum J. Agardh (Phaeophyceae, Ochrophyta): from hatchery to out-planting

The brown seaweed Sargassum siliquosum is among the most common species with economic potential in the Philippines. However, reports on its culture are non-existent. This study describes the culture of S. siliquosum from land-based hatchery to out-planting in the open sea. Zygotes released from female receptacles can be recruited in large quantities unto artificial substrates and within 24 h produce multicellular embryos characterized by multiple bundles of rhizoids, and after 48–72 h elongated into germlings. After 2.5 months, germlings formed cauline leaves, and after 4 months, developed branches as seedlings. Recruits favored clay substrate than limestone and nylon in terms of density, growth, and longevity of seedlings. Desiccation treatment at different periods resulted to lower recruit density compared with control, had inferior growth and shorter longevity in all substrate types. For a period of 16 months, growth of S. siliquosum in the hatchery tanks was very slow, but became faster when out-planted in open sea using suspension culture method. Cultivars developed more branches after 4 months, at the same time producing receptacles. Maximum growth was achieved after 6 months, reaching a mean length of 42.8 ± 30.9 cm (max recorded was 1 m), some cultivars starting to show signs of senescence. In contrast, seedlings deployed using the bottom culture method survived for 3 months only without signs of further growth mainly due to epiphytism, siltation, and grazing. In conclusion, this study demonstrated the feasibility of farming S. siliquosum from hatchery-produced seedlings using suspension culture method to produce biomass for commercial use.

Bioactive properties of Sargassum siliquosum J. Agardh (Fucales, Ochrophyta) and its potential as source of skin-lightening active ingredient for cosmetic application

Bioactive properties of Sargassum siliquosum J. Agardh (Fucales, Ochrophyta) and its potential as source of skin-lightening active ingredient for cosmetic application

Sargassum siliquosum J. Agardh extract as potential material for synthesis of bioplastic film

In this study, alginate extracted from the brown alga Sargassum siliquosum J. Agardh was used as raw material for the synthesis of bioplastic film. Two-level full factorial design (FFD) and augmented central composite design (CCD) were employed in analysing the effects of following parameter toward the physical properties of the film produced: alginate loading, addition of sago starch and sorbitol as well as the concentration of calcium chloride (CaCl2) used during treatment process. Statistical analysis of results indicated that bioplastic film could be produced from S. siliquosum by using a mixture containing 2 g of extracted alginate powder and 15% w/w of sorbitol followed by the treatment with 75% w/w of CaCl2. Model validation proved that the percentage error was below 3.21% in general, indicating the proficiency of the models in predicting an optimised film with the following properties: tensile strength of 33.90 MPa, elongation at break of 3.58%, water vapour permeability of 2.63 × 10−10 g Pa−1 s−1 m−1 and water solubility of 33.73%.

Application of Two-Level Full Factorial Design for the Extraction of Fucoxanthin and Antioxidant Activities from Sargassum siliquosum and Sargassum polycystum

ABSTRACTTwo-level full factorial design was employed to identify the extraction parameters that can improve the derivation of fucoxanthin content (FC), total carotenoid content (TCC), and antioxidant from two brown seaweeds, Sargassum siliquosum (SS) and Sargassum polycystum (SP). These parameters included temperature (A: 4–45°C), time (B: 30–1,440 min), and solvent-to-solid ratio (C: 10–50 ml/g). Antioxidant activities were determined as trolox equivalent antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, and ferric-reducing antioxidant power (FRAP). Results showed that all three factors were significant (p < 0.05) in providing higher FC in both species. These factors were also significant in obtaining higher TCC in SS; whereas in SP, TCC was only affected by solvent-to-solid ratio. Only temperature was found to contribute significantly to a higher TEAC in both species. However, none of the factors improved DPPH for SS, except temperature and time for SP. For SS, only time was significant in obtaining higher FRAP; whereas temperature and time were significant for SP. Hence, results indicate that a simple modification in the extraction temperature, time, and solvent-to-solid ratio will be able to improve the derivation of fucoxanthin, carotenoids, and antioxidant activities.

Characterizing the Three Different Alginate Type of Sargassum siliquosum

This research was aimed to identify the brown seaweed, to characterize the acid, sodium and calcium alginate, and to examine the alginate yield. The identification was done phaenotypically. The extraction method was pretreated by ethanol depigmentation, followed by the extraction of Na2CO3/EDTA and CaCl2 and presipitated with absolute ethanol. The characterization of alginate was done by FT-IR spectroscopy and Thin Layer Chromatography by comparing the samples with standard alginate (Sigma, USA). The key of identification showed that the species was Sargassum siliquosum. There are similarities in signal vibration and TLC spots among the samples and the standard. The TLC test was also showed that those alginates contain mannuronic and guluronic acid. The highest yield was produced by Sodium alginate (40,34% + 0,21), followed by Acid alginate (11,51% + 0,15) and Calcium alginate (4,8% + 0,09). Keywords: alginate, characterization, Sargassum siliquosum, yield

Malaysian brown seaweeds Sargassum siliquosum and Sargassum polycystum: Low density lipoprotein (LDL) oxidation, angiotensin converting enzyme (ACE), α-amylase, and α-glucosidase inhibition activities

Two Malaysian brown seaweeds, Sargassum siliquosum and Sargassum polycystum were first extracted using methanol to get the crude extract (CE) and further fractionated to obtain fucoxanthin-rich fraction (FRF). Samples were evaluated for their phenolic, flavonoid, and fucoxanthin contents, as well as their inhibitory activities towards low density lipoprotein (LDL) oxidation, angiotensin converting enzyme (ACE), α-amylase, and α-glucosidase. In LDL oxidation assay, an increasing trend in antioxidant activity was observed as the concentration of FRF (0.04–0.2mg/mL) and CE (0.2–1.0mg/mL) increased, though not statistically significant. As for serum oxidation assay, significant decrease in antioxidant activity was observed as concentration of FRF increased, while CE showed no significant difference in inhibitory activity across the concentrations used. The IC50 values for ACE inhibitory activity of CE (0.03–0.42mg/mL) were lower than that of FRF (0.94–1.53mg/mL). When compared to reference drug Voglibose (IC50 value of 0.61mg/mL) in the effectiveness in inhibiting α-amylase, CE (0.58mg/mL) gave significantly lower IC50 values while FRF (0.68–0.71mg/mL) had significantly higher IC50 values. The α-glucosidase inhibitory activity of CE (IC50 value of 0.57–0.69mg/mL) and FRF (IC50 value of 0.50–0.53mg/mL) were comparable to that of reference drug (IC50 value of 0.54mg/mL). Results had shown the potential of S. siliquosum and S. polycystum in reducing cardiovascular diseases related risk factors following their inhibitory activities on ACE, α-amylase and α-glucosidase. In addition, it is likelihood that FRF possessed antioxidant activity at low concentration level.

Innate immune-stimulating and immune genes up-regulating activities of three types of alginate from Sargassum siliquosum in Pacific white shrimp, Litopenaeus vannamei.

The Total Haemocyte Count (THC), phenoloxidase (PO), Superoxide Dismutase (SOD) activity, Phagocytic Activity/Index and Total Protein Plasma (TPP) were examined after feeding the white shrimp Litopenaeus vannamei with diets supplemented with three different types of alginates (acid, calcium and sodium alginates). Immune-related genes expression was evaluated by quantitative Real Time PCR (qRT-PCR). Results indicated that the immune parameters directly increased according to the doses of alginates and time. The 2.0gkg(-1) of acid and sodium alginate treatments were gave better results. Four immune-related genes expression i.e. LGBP, Toll, Lectin, proPO were up regulated. It is therefore concluded that the supplementation of alginate of Sargassum siliquosum on the diet of L.vannamei enhanced the innate immunity as well as the expression of immune-related genes. It is the first report on the simultaneous evaluation of three alginate types to enhance innate immune parameters and immune-related genes expression in L.vannamei.

Bioactivity of crude ethanolic and hexane extracts from Sargassum siliquosum JG agardh against fish pathogens

Microorganisms pathogenic to fish lead to morbidity-linked economic losses and pose threat to human and animal health. Organisms that have potent antimicrobial properties against fish pathogens include brown seaweeds. This study determined the antimicrobial activity of the crude extracts of Sargassum siliquosum through Disc Diffusion Assay. The ethanol extract of S. siliquosum was found to exhibit antibacterial activity against P. aeruginosa, P. vulgaris and A. hydrophila with zones of inhibition of 13.17 ± 0.42 mm and 16.08 ± 1.81 mm and 12.52 ± 2.17 mm, respectively. The hexane extract had a 16.0 ± 0 mm zone of inhibition against P. vulgaris. This investigation reveals that S. siliquosum is a potential source of bioactive compounds against disease-causing fish pathogens.

A simple and effective method for RNA isolation and cDNA library construction from the brown seaweed Sargassum polycystum (Fucales, Phaeophyceae)

The isolation of high-quality RNA from brown seaweeds has always been problematic due to a high content of polyphenolic compounds and polysaccharides in their tissues. This study presents a simple and effective method for isolating high-quality RNA from the brown seaweeds Sargassum (Sargassum polycystum, Sargassum siliquosum, Sargassum baccularia, and Sargassum binderi), Padina tetrastromatica, Turbinaria conoides, Dictyota sp., and Hormophysa cuneiformis using cetyltrimethylammonium bromide and selective lithium chloride precipitation. Approximately 25–43 μg g−1 fresh weight of total RNA was obtained from these brown algae. The A 260/A 280 absorbance ratio of these RNA samples are between 1.995 ± 0.027 and 2.122 ± 0.013, with distinct 28S and 18S ribosomal RNA bands visible on a formaldehyde agarose gel. The RNA obtained from S. polycystum was found to be suitable for many downstream applications such as reverse transcription polymerase chain reaction, cloning, synthesis of cDNA, and construction of cDNA library for the generation of expressed sequence tags.

Seasonal growth rate of Sargassum species at Teluk Kemang, Port Dickson, Malaysia

The seasonal growth rates of three Sargassum species were studied along two reef flats of Teluk Kemang, located at Port Dickson, Malaysia from September 2009 to September 2010. Systematic quadrat and line transects were sampled monthly. Nondestructive sampling was conducted, whereby Sargassum plants were tagged and monitored for a 13-month period. The majority of the tagged Sargassum samples belonged to lower length classes (<200 mm), especially in 0–99 mm (Sargassum polycystum, 64.20 %; Sargassum binderi, 68.29 %; Sargassum siliquosum, 56.80 %). Analysis of the monthly mean thallus length (MTL) revealed a bimodal pattern in growth rates, with two periods of high growth rates (January–February 2010 and June–July 2010) and two periods of higher degenerative rates (April 2010 and September 2010). The highest growth rates were recorded in February 2010 (4.08 mm day−1) for S. siliquosum, and in June for S. polycystum (2.54 mm day−1) and S. binderi (1.89 mm day−1). Redundancy analysis (RDA) was employed to test for the overall correlation between monthly variation in MTL and the environmental parameters measured; S. binderi was correlated with ambient temperature (r = 0.5395), while S. siliquosum was correlated with seawater salinity (r = 0.5419) and ammonia (r = −0.4603). This study reviews the seasonality of Sargassum species on two reefs of Teluk Kemang and their correlation with the selected environmental parameters.

Extraction and characterisation of alginate from brown seaweeds (Fucales, Phaeophyceae) collected from Port Dickson, Peninsular Malaysia

Four species of brown seaweeds, namely Sargassum baccularia, Sargassum binderi, Sargassum siliquosum and Turbinaria conoides, harvested from Port Dickson, Negeri Sembilan, Malaysia were analysed for ash content, alginate yield and alginate properties. Seaweeds calcined at 450°C were found to have low amount of non-combustible residue as these were not contaminated by calcareous animals. Alginate was extracted from these seaweeds by two methods: hot and cold. In the hot method, the storing time was 3 h and the processing temperature was 50°C, whilst in the cold method, the sample was stored overnight at room temperature. Higher yield of alginate was obtained by the hot method compared to the cold method, but alginate extracted by the cold method gave higher molecular weight. In the hot method, 49.9% of alginate was extracted from S. siliquosum, followed by T. conoides (41.4%), S. binderi (38.9%) and S. baccularia (26.7%). Alginate extracted from T. conoides has an average molecular weight, M w, of 8.06 × 105 g mol−1, whereas alginate from S. siliquosum was the lowest in M w (4.81 × 105 g mol−1) when the extraction was done at room temperature. Alginate extracted from S. baccularia was found to be very heat-sensitive. Its M w has dropped more than 83%, from 7.52 × 105 to 1.23 × 105 g mol−1, when the extraction temperature was raised. The effect of heat on the extent of depolymerisation of the alginate molecule of the other three brown seaweed species was less significant, with decrease in molecular weight ranging between 13% and 16%.

Effects of nutrient enhancement on the fecundity of a coral reef macroalga

On coral reefs, there is concern that increased nutrient supply (e.g. due to eutrophication) causes increased algal growth and hence increased algal abundance, in turn causing colonisation and invasions of coral populations, resulting in reef degradation, or a coral–algal phase shift. For example, species of Sargassum, a highly seasonal, large, brown seaweed, are suggested to be colonising corals on inshore coral reefs of the Great Barrier Reef, as a result of anthropogenic increases in terrestrial runoff of sediments and nutrients. However, implicit in this argument is the assumption that nutrient-related increases in growth will lead to increased fecundity (and/or propagule success), since without such changes, increased abundance can only occur by vegetative means. Whilst plausible, there is no experimental evidence for this assumption in coral reef algae. We here present an initial study in which experimental increases in nutrient supply apparently did not lead to increased fecundity of Sargassum siliquosum; rather, density and biomass of receptacles were reduced in nutrient-enhanced algae. There was little effect of nutrient treatments on the proportional allocation of biomass to reproductive and vegetative structures: nutrient enhancement led to similar decreases in biomass of reproductive and vegetative tissue. Tissue nutrient levels indicated effective enhancement of nitrogen supply, although phosphorus levels were not different across nutrient treatments. The reduced fecundity with increased nutrients may reflect either a genuine inhibition by higher nutrient levels, as found in previous studies, or accelerated maturation, causing increased tissue losses due to more advanced seasonal senescence. Either way, this exploratory experiment provides initial evidence that nutrient effects on tropical coral reef macroalgae may be complex, and does not support the assumption that increased nutrient supply will result in a numeric increase in populations of Sargassum spp. Our results should not be taken as an unequivocal demonstration that nutrients inhibit fecundity overall, but illustrate the need to distinguish between effects on different life-history processes (e.g. growth and reproduction). For increased growth of pre-existing individuals to contribute to algal invasions and phase shifts, that growth must result in either increased fecundity, or increased propagule success.

ASSESSMENT OF TEMPERATURE AND NUTRIENT LIMITATION ON SEASONAL DYNAMICS AMONG SPECIES OF SARGASSUM FROM A CORAL REEF IN SOUTHERN TAIWAN1

The effects of temperature and nutrient availability on seasonal abundance were compared among Sargassum berberifolium J. Ag., S. polycystum C. Ag., S. siliquosum J. Ag., and S. sandei from a reef in southern Taiwan. Growth temperature limits and optimum were variable between species and between developmental stages. Growth temperature ranges agree with Sargassum periodicity except S. sandei. Sargassum siliquosum can tolerate high temperature as indicated by higher optimum temperature and tolerance limits. Temporal changes in tissue nutrient content and alkaline phosphatase activity and the results from nutrient enrichment bioassay show that S. sandei, S. berberifolium, and S. polycystum are P limited in the early growth period and then N limited, whereas S. siliquosum showed a contrasting trend, reflecting the type of nutrient limitation is variable by time and between species. A smaller nutrient threshold for maximum growth in S. berberifolium, S. polycystum, and S. siliquosum than in S. sandei and higher growth rate in S. berberifolium and S. polycystum indicate the higher growth vigor and nutrient utilization efficiency, the higher abundance. High N reserves in S. berberifolium and S. polycystum exposed to elevated seawater N in the early growth period supported the subsequent growth. The multiple regression analysis indicates that percent cover of S. siliquosum increased with increasing water temperature and dissolved inorganic nitrogen concentrations, whereas that of S. polycystum decreased with increasing water temperature. In conclusion, seasonal dynamics of Sargassum spp. from southern Taiwan are attributable to species and temporal variations in temperature limitation and nutrient utilization strategy.

1H-NMR study of Na alginates extracted from Sargassum spp. in relation to metal biosorption.

The use of a number of species of marine brown algae in the implementation of bioremediation strategies for toxic heavy metals is being considered and evaluated. The biosorption capacity of these algae for heavy metals resides mainly in a group of linear polysaccharides known as alginates that occur as a gel in the algal thallus. The potential for selective metal binding by the biomass of two species of Sargassum was evaluated by 1H-NMR (nuclear magnetic resonance) following a high temperature, alkaline extraction and purification of their alginate polysaccharide. The alkaline extraction protocol applied to Sargassum fluitans and Sargassum siliquosum yielded alginate samples of low viscosity, suitable for direct acquisition of well-resolved spectra. Estimates of both the ratio of beta-D-mannopyranuronosyl (M) and alpha-L-gulopyranuronosyl (G) residues along the polymer chain and the frequencies of occurrence of diad uronic acid residue pairs were obtained. Guluronic acid (G) was the major component in all extracts and the GG diads accounted for more than 49% of the polymer diads. Whereas the performance of Sargassum spp. in the metal biosorption process is a function of both its alginate content and composition, the occurrence of "G-blocks" in both purified alginates and in the raw brown seaweed is critical because it results in a well-established selectivity for divalent ions, potentially increasing the commercial effectiveness of targeted biosorption as a means of remediation.