Gracilaria Bursa-pastoris Research Articles

Chemical composition and nutrient profiles of nine red macroalgae species

Nine red macroalgae (Amphiroa rigida, Gracilaria bursa-pastoris, Gracilaria gracilis, Grateloupia torture, Jania rubens, Laurencia obtusa, Laurencia pyramidalis, Liagora viscida, and Pterocladiella capillaries) were collected from coastal waters of Türkiye, and their proximate, fatty acid, soluble carbohydrate, and mineral profiles were investigated in the present study. According to the results, the crude protein content of the samples was between 4% and 23.8%, and four of the samples (G. turuturu, L. obtusa, L. pyramidalis, and P. capillacea) contained more than 10% protein. The crude lipid content of all the samples was below 1.6%, and the total carbohydrate content was between 38.3% and 76.9%. The macroalgae samples were generally richer in saturated fatty acids, palmitic acid being the most abundant, whereas G. gracilis had the highest content of unsaturated fatty acids (55.8%). All samples exhibited high contents of myo-inositol or glucose. Also, the samples generally had a good composition of minerals. Still, the heavy metal (i.e., Pb and Cd) content of Gracilaria gracilis was higher (59.6 µg/kg, P < 0.05) than those of the other algae samples. This study provides valuable insight into the chemical composition and fatty acid, mineral, and soluble carbohydrate profiles of Amphiroa rigida, Gracilaria bursa-pastoris, Gracilaria gracilis, Grateloupia turuturu, Jania rubens, Laurencia obtusa, Laurencia pyramidalis, Liagora viscida, and Pterocladiella capillacea from Türkiye.Graphical

A statistical optimization for almost-complete methylene blue biosorption by Gracilariabursa-pastoris

In this study, the dried biomass of four marine algae, namely Porphyra sp., Gracilaria bursa-pastoris, Undaria pinnatifida and Laminaria sp., were screened for their ability to remove methylene blue (MB) dye from aqueous solutions. Statistical approaches of the Plackett-Burman Design (PBD) and Box-Behnken Design (BBD) were applied to optimize different environmental conditions in order to achieve the maximum MB removal percentage by Gracilaria bursa-pastoris. The biosorbent was characterized before and after adsorption process using FTIR, XRD and SEM analysis. Additionally, isotherms, kinetics and thermodynamics studies were conducted to investigate the adsorption behavior of the adsorbent. The results showed that Gracilaria bursa-pastoris achieved the highest dye removal efficiency (98.5 %) compared to 96.5 %, 93.5 % and 93.9 % for Undaria pinnatifida, Porphyra sp. and Laminaria sp., respectively. PBD analysis revealed that the agitation speed, pH, and biomass dose were found to be the significant parameters affecting MB removal onto Gracilaria dried biomass. According to the BBD results, the maximum dye removal percentage (99.68 %) was obtained at agitation speed of 132 rpm, pH 7 and biomass dose of 7.5 g/L. FTIR, XRD and SEM analysis demonstrated the participation of several functional groups in the adsorption process and changes in the cell surface morphology of the adsorbent following the dye adsorption. The adsorption isotherms showed better fit to Freundlich model (R2 = 0.9891) than the Langmuir, Temkin, and Dubinin-Radushkevich models. The adsorption kinetics were best described by the pseudo-second-order model (R2 = 0.9999), suggesting the chemical interactions between dye ions and the algal biomass. The thermodynamic parameters indicated that the adsorption of MB onto Gracilaria dried biomass was spontaneous, feasible, endothermic and random. These results indicate that dried biomass of Gracilaria bursa-pastoris is an attractive, environmentally friendly, cheap and effective agent for MB dye removal from environmental discharges.

Study of the Phytochemical Composition, Antioxidant Properties, and In Vitro Anti-Diabetic Efficacy of Gracilaria bursa-pastoris Extracts.

In this study, a comparison was made of the chemical makeup of different extracts obtained from Gracilaria bursa-pastoris, a type of red seaweed that was gathered from the Nador lagoon situated in the northern part of Morocco. Additionally, their anti-diabetic and antioxidant properties were investigated. The application of GC-MS technology to analyze the fatty acid content of the samples revealed that linoleic acid and eicosenoic acid were the most abundant unsaturated fatty acids across all samples, with palmitic acid and oleic acid following in frequency. The HPLC analysis indicated that ascorbic and kojic acids were the most prevalent phenolic compounds, while apigenin was the most common flavonoid molecule. The aqueous extract exhibited significant levels of polyphenols and flavonoids, registering values of 381.31 ± 0.33 mg GAE/g and 201.80 ± 0.21 mg QE/g, respectively. Furthermore, this particular extract demonstrated a remarkable ability to scavenge DPPH radicals, as evidenced by its IC50 value of 0.17 ± 0.67 mg/mL. In addition, the methanolic extract was found to possess antioxidant properties, as evidenced by its ability to prevent β-carotene discoloration, with an IC50 ranging from 0.062 ± 0.02 mg/mL to 0.070 ± 0.06 mg/mL. In vitro study showed that all extracts significantly inhibited the enzymatic activity of α-amylase and α-glucosidase. Finally, molecular docking models were applied to assess the interaction between the primary phytochemicals identified in G. bursa-pastoris extracts and the human pancreatic α-amylase and α-glucosidase enzymes. The findings suggest that these extracts contain bioactive substances capable of reducing enzyme activity more effectively than the commercially available drug acarbose.

Antioxidant Activity and Inhibition of Liver Cancer Cells' Growth of Extracts from 14 Marine Macroalgae Species of the Mediterranean Sea.

Macroalgae exhibit beneficial bioactivities for human health. Thus, the aim of the present study was to examine the antioxidant and anticancer potential of 14 macroalgae species' extracts, namely, Gigartina pistillata, Gigartina teedei, Gracilaria gracilis, Gracilaria sp., Gracilaria bursa pastoris, Colpomenia sinuosa, Cystoseira amentacea, Cystoseira barbata, Cystoseira compressa, Sargassum vulgare, Padina pavonica, Codium fragile, Ulva intestinalis, and Ulva rigida, from the Aegean Sea, Greece. The antioxidant activity was assessed using DPPH, ABTS•+, •OH, and O2•- radicals' scavenging assays, reducing power (RP), and protection from ROO•-induced DNA plasmid damage assays. Moreover, macroalgae extracts' total polyphenol contents (TPCs) were assessed. Extracts' inhibition against liver HepG2 cancer cell growth was assessed using the XTT assay. The results showed that G. teedei extract's IC50 was the lowest in DPPH (0.31 ± 0.006 mg/mL), ABTS•+ (0.02 ± 0.001 mg/mL), •OH (0.10 ± 0.007 mg/mL), O2•- (0.05 ± 0.003 mg/mL), and DNA plasmid breakage (0.038 ± 0.002 mg/mL) and exhibited the highest RP (RP0.5AU 0.24 ± 0.019 mg/mL) and TPC (12.53 ± 0.88 mg GAE/g dw). There was also a significant correlation between antioxidant activity and TPC. P. pavonica (IC50 0.93 ± 0.006 mg/mL) exhibited the highest inhibition against HepG2 cell growth. Conclusively, some of the tested extracts exhibited significant chemopreventive properties, and so they may be used for food products.

Antibacterial Activities of Methanolic Extracts of Different Seaweeds from Iskenderun Bay, Turkey

Antibacterial activities of the methanolic extracts of Stypopodium schimperi (Kützing) Verlaque and Boudouresque, Halopteris filicina (Grateloup) Kützing, Dictyota dichotoma (Hudson) J.V.Lamouroux, Gracilaria bursa-pastoris (S.G.Gmelin) P.C.Silva, Ulva intestinalis Linnaeus species from the Iskenderun Bay, Turkey against Escherichia coli, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhimurium and Proteus vulgaris were evaluated by using the microdilution method. Results of the study showed that all of the extracts had an antimicrobial effect on the tested bacteria. A minimum inhibitor concentration and minimum bactericidal concentrations of the extracts ranged from &amp;gt;125 to &amp;lt;0.39 mg mL-1. Furthermore, this is the first report on antibacterial effects of the methanolic extracts of S. schimperi (Kützing) Verlaque and Boudouresque and G. bursa-pastoris (S.G.Gmelin) P.C.Silva species. The present findings revealed that all studied seaweed species could act as a natural source of bioactive compounds for the treatment of infectious diseases.

Growth rates of Gracilariopsis longissima, Gracilaria bursa-pastoris and Chondracanthus teedei (Rhodophyta) cultured in ropes: implication for N biomitigation in Cadiz Bay (Southern Spain)

Cultures of three native macroalgal species (Gracilariopsis longissima, Gracilaria bursa-pastoris and Chondracanthus teedei) were developed in open coastal waters of a shallow, potentially eutrophic bay in Southern Spain. Experimental trials to assess the technical feasibility of seaweed cultivation and nitrogen biofiltration potential were conducted between October 2014 and December 2015. Seaweeds were cultivated using submersible rafts in five periods of 9 weeks to identify the most suitable seasons and culture duration (3, 6 or 9 weeks). Using generalized linear models (GLMs), the most relevant environmental factors controlling the growth of the three seaweeds were identified. Maximum net growth rates varied between 1.39% day−1 in C. teedei (winter, 6 weeks) and 4.71% day−1 in G. longissima (autumn, 3 weeks). Overall, the best period to cultivate seaweeds in Cadiz Bay was from mid-winter to early summer. No clear effects of duration of the culture were observed for C. teedei and G. bursa-pastoris. Short culture periods of 3 weeks were more suitable for G. longissima. Tissue N contents generally were lower than the critical quota, and GLMs suggested a critical role of N limiting seaweed growth in this bay. Dissolved inorganic nitrogen was biofiltered from winter to early summer and revealed G. bursa-pastoris as the main biomitigator of nitrogen (up to 80 mg N m−1 month−1 in spring). This species also showed positive growth rates virtually during the entire study period and was the most suitable species for cultivation in this area.

Temporal variation and structure of macro-epifauna associated with macrophytes in the Bizerte lagoon (Tunisia, SW Mediterranean Sea)

ABSTRACTThe temporal variation in composition and abundance of the macro-epifauna associated with seaweeds (Ulva lactuca, Cladophora sp., Gracilariopsis longissima and Gracilaria bursa-pastoris) and seagrass (Cymodocea nodosa) was investigated at Menzel Jemil station in the Bizerte lagoon. Twelve replicate samples (25 x 25 cm frame) were collected monthly from October 2009 to September 2010. Sampling data yielded 21,575 invertebrate specimens from floating seaweeds and the seagrass, belonging to 40 taxa, of which 18 species were arthropods, 13 molluscs, three echinoderms, three fishes, two polychaetes and one cnidarian. Crustaceans were the most dominant and the most species-rich group and Idotea balthica basteri the most abundant species, accounting for 28.94% of the total abundance. Minimum (9.25 ± 5.56 species) and maximum (19.75 ± 3.2 species) values of mean species richness were observed in December and June, respectively. Species richness and density of macro-epifauna showed similar trends to plant biomass and the highest values of both indices coincided with periods of maximal plant biomass. Mean values of Shannon’s index H′ and evenness J′ were low, ranging from 0.34 ± 0.02 bit to 1.08 ± 0.06 bit, and from 0.23 ± 0.03 to 0.52 ± 0.07, respectively. The high dominance of herbivores and detritivores highlighted the substantial role played by macrophytes as food source for associated macro-epifauna species. Multivariate analyses also indicated significant seasonal differences for the macro-epifauna assemblage and revealed significant relationships with environmental variables. According to the canonical correspondence analysis, concentrations of phosphates and nitrites, and temperature were the variables that explained the variation of the macro-epifauna abundance in the Bizerte lagoon.

Evaluation of antioxidant activity and total phenol content of Gracilaria bursa-pastoris harvested in Nador lagoon for an enhanced economic valorization

BackgroundThe Gracilaria bursa-pastoris is an abundant alga that is responsible for the eutrophication in Nador lagoon in Morocco. Therefore, the lagoon is a deposit of bioresources whose economic value can be enhanced. Antioxidative properties of seaweed extracts have been studied in several geographic regions, but only a few studies have been performed on tropical seaweed species, and no research has been done to determine antioxidant activity and valorization of the indigenous algae in Nador lagoon in Morocco.MethodsThe present study evaluated the antioxidant potential of methanolic and aqueous extracts from Gracilaria bursa-pastoris by measuring the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and total content of phenolic, flavonoids and flavonols content in each extract.ResultsThis study showed that this macroalgae contained a high total phenolic content (142.26 and 79.43 mg GAE g−1 extract) for ethanolic and aqueous extracts, respectively. All extracts exhibited a DPPH radical scavenging activity, and the methanolic extracts demonstrated a great antioxidant potential with very low value of EC50 (0.085 mg/mL), significantly equivalent to EC50 (0,028 mg/mL) of commercial antioxidant ascorbic acid. These results suggest that the macroalgae have a great antioxidant potential which could be considered for future applications in medicine, food production or cosmetic industry in Morocco.ConclusionsThis work showed that the ethanolic extract was rich in phenolic compounds. This extract exhibited the highest antioxidant activity which may be explained by the presence of a large quantity of phenolic compounds. The Gracilaria bursa-pastoris can be utilized as a source of natural antioxidant compounds.

Comparison of energy recovery after anaerobic digestion of three Marchica lagoon algae (Caulerpa prolifera, Colpomenia sinuosa, Gracilaria bursa-pastoris)

The Marchica lagoon, which currently suffers from eutrophication caused by algae proliferation, is one of the largest lagoons in the Mediterranean. In this work, we valorised the three important algae (Caulerpa prolifera, Gracilaria bursa-pastoris, and Colpomenia sinuosa) that are responsible for pollution of the lagoon, by determining their biogas production and green energy capacities and studying their effects on anaerobic bacteria. The red alga Gracilaria bursa-pastoris produced the most biogas with 86.35ml/g VS, which is equivalent to 514.99kWh/t VS of green energy, whereas the brown alga Colpomenia sinuosa ranked second with 74.68ml/g VS of biogas product, the equivalent to 445.39 kWh/tVS. Thus, these two algae were considered excellent substrates for anaerobic digestion. The green alga Caulerpa prolifera produced the least biogas with only 24.53ml/g VS and green energy of 146.29kWh/t VS. These results correlated with the anaerobic bacterial proliferation of the inoculum, where Gracilaria bursa-pastoris led to a large proliferation of anaerobic bacteria, from 0.19×106CFU/g to 7×106CFU/g, followed by the brown alga and the green alga. Therefore, we consider these three Marchica lagoon algae (Caulerpa prolifera, Gracilaria bursa-pastoris, and Colpomenia sinuosa) as an exploitable energy reservoir. Finally, we propose that a plant, comprising anaerobic digestion of the three algae, be installed to produce energy and a lagoon aerator to dissolve the atmospheric oxygen inside the lagoon. This will halt eutrophication of the Marchica lagoon.

Distribution of four isopods (Peracarida: Crustacea) in shallow waters of the Bizerte Lagoon (Tunisia, SW Mediterranean Sea)

The distribution of four isopods – Idotea balthica basteri (Pallas, 1772), Idotea chelipes mediterranea Charfi-Cheikhrouha, 1996, Sphaeroma serratum (Fabricius, 1787), and Paracerceis sculpta (Holmes, 1904) – at Menzel Jemil (Bizerte Lagoon, North Tunisia) was analysed and then related to the variation of temperature, depth and plant biomass. The abundance of isopods showed monthly fluctuations with maxima in August and minima in December 2010. The most dominant species was I. b. basteri followed by S. serratum, with a spatial gradient in the distribution pattern of isopod species in the study area. The high density of juveniles in algae and seagrass highlights the important role played by this habitat as a nursery for species. Both dominant species were tolerant to temperature variations, with some preference values (19.73–27.73°C in I. b. basteri; up to 28°C in S. serratum) and salinity (36.7–38.6 psu in I. b. basteri; 39–39.2 psu in S. serratum). Multiple regression analysis between environmental variables and species abundance showed a positive relationship with biomass of Gracilaria bursa-pastoris and Ulva lactuca for the two species of Idotea and Sphaeroma, respectively, while abundance of P. sculpta was positively related to temperature. Biotic and environmental linking (BIOENV) analysis confirmed the greatest influence of temperature and vegetation biomass on the temporal distribution of these isopod species. A spatial distribution pattern according to successive depths was revealed.

Bioactivity of Phycocolloids against the Mediterranean Protozoan Leishmania infantum: An Inceptive Study

Sulfated polysaccharides from marine macroalgae have been shown to possess a variety of biological activities against fungi, bacteria, viruses, and protozoa. In this study, the in vitro activity of algal polysaccharides against Leishmania infantum (Kinetoplastida: Trypanosomatidae) was investigated. The polysaccharides were extracted from different macroalgae of the Mediterranean Sea: Chaetomorpha linum, Agardhiella subulata, Gracilaria viridis, Gracilaria bursa-pastoris, Hypnea cornuta, Sargassum muticum, and Undaria pinnatifida. Preliminary results showed a good anti-leishmanial activity of the investigated species, encouraging the focus on their use as natural resources in order to match integrated management strategies for the employment of local macroalgae.

Growth, protein and carbohydrate contents in Ulva rigida and Gracilaria bursa-pastoris integrated with an offshore fish farm

Low-technology practices are generally the rule when cultivating marine macroalgae, and they do not necessarily comply with sustainability requirements. When integrated with other marine organisms in land-based setups, seaweed culture can be sustainable also providing environmental benefits. Major challenges of such integrated aquaculture systems, however, are in sea-based setups. The current study examined the growth rates of Ulva rigida and Gracilaria bursa-pastoris, as well as their protein and carbohydrate contents, when exposed to different distances from an offshore, fed-fish cage system. Nutrient levels in seawater were consistently high downstream from the fish cages, significantly enhancing the specific growth rates and cellular contents of starch and soluble protein in these two seaweeds. Specifically, daily maximal growth rates were 17 % day−1 for U. rigida and 10 % day−1 for G. bursa-pastoris, maximal starch contents were 22 and 21 %, respectively, and maximal protein contents were on a dry weight basis 7 and 13 %, respectively. When repositioned at low ambient nutrient levels for 48 h, the starch and the carbohydrate levels increased by 129 and 131 % for U. rigida and by 198 and 150 % for G. bursa-pastoris, respectively. Altogether, this study supports implementing future viable mean of sustainable macroalgae cultivation by taking advantage of excessive nutrients released from an offshore fish farm.

Gracilaria bursa-pastoris (Gmelin) Silva Extract Attenuates Ultraviolet B Radiation-Induced Oxidative Stress in Human Keratinocytes

The purpose of this study was to assess the protective effects of an ethanol extract derived from the red alga Gracilaria bursa-pastoris (Gmelin) Silva (GBE) on ultraviolet B (UVB)-irradiated human HaCaT keratinocytes. GBE exhibited scavenging activity against intracellular reactive oxygen species that were induced by either hydrogen peroxide or UVB radiation. In addition, both the superoxide anion and the hydroxyl radical were scavenged by GBE in cell-free systems. GBE absorbed light in the UVB range (280-320 nm) of the electromagnetic spectrum and lessened the extent of UVB-induced oxidative damage to cellular lipids, proteins, and DNA. Finally, GBE-treated keratinocytes showed a reduction in UVB-induced apoptosis, as exemplified by fewer apoptotic bodies. These results suggest that GBE exerts cytoprotective actions against UVB-stimulated oxidative stress by scavenging ROS and absorbing UVB rays, thereby attenuating injury to cellular constituents and preventing cell death.

Effect of depth on growth and pigment contents of the macroalgae Gracilaria bursa-pastoris

The effects of environmental parameters on biomass, growth and pigment content of the red seaweed Gracilaria bursa-pastoris (S.G. Gmel.) P.C. Silva was investigated under field conditions in Thau Lagoon (France). The seaweed was cultivated in cages placed at three depths (1.0, 2.0 and 4.0 m) over a one-year period. The results showed elevated biomass and growth values in the spring and autumn, when temperature, light and photoperiod values were similar. The highest specific growth rates (SGR) were obtained at 1.0 m (4.95±0.29% day-1) and 2.0 m (4.45±0.33% day-1). At a depth of 4.0 m, the seaweed never exceeded 2% day-1 and obtained null values in the summer. The concentrations of phycoerythrin (RPE) and chlorophyll (CHL a) showed maximum values in the winter and minimum values in the summer. This evolution was related to water temperature, light intensity and nitrogen content in the algal tissue. The results obtained in this study show that the water depth influenced the growth and pigment composition of G. bursa-pastoris.

Determination of the Phenolic Compounds and Antioxidative Capacity in Red Algae Gracilaria bursa-pastoris

There is an increasing demand for natural antioxidant molecules in order to replace the synthetic additives in the food industry. Gracilaria bursa-pastoris (Gmelin) Silva was analyzed to determine its bioactive components including; the total phenolic content, total antioxidant capacity (lipid and water-soluble), vitamins (A, E and C), total protein and total carbohydrate content. In addition, the bioactive components of Gracilaria bursa-pastoris were compared with some plants and seaweeds having antioxidant capacity. This study showed that Gracilaria bursa-pastoris contained a high total phenolic content, vitamin E, vitamin C and the antioxidant capacity. Gracilaria bursa-pastoris can be utilized as a source of natural antioxidant molecules and could be useful for food industry.

Evaluation of three seaweeds Gracilaria bursa-pastoris, Ulva rigida and Gracilaria cornea as dietary ingredients in European sea bass ( Dicentrarchus labrax) juveniles

The aim of this study was to evaluate the inclusion of three seaweeds Gracilaria bursa-pastoris (GP), Ulva rigida (UR) and Gracilaria cornea (GC) as dietary ingredients on the performance, nutrient utilisation and body composition of European sea bass juveniles. Six experimental diets were formulated to replace 5% (GP-5, UR-5, and GC-5 Diets) and 10% (GP-10, UR-10 and GC-10 Diets) fish protein hydrolysate (CPSP) by each of the three seaweeds. A control diet was used, without inclusion of any seaweed. Diets were fed to duplicate groups of 25 European sea bass ( Dicentrarchus labrax) juveniles (IBW = 4.7 g) for 10 weeks. Growth performance was only significantly reduced ( P < 0.05) in fish fed the GC-10 diet, whereas the feed conversion ratio increased significantly in those fish. The apparent digestibility coefficients of dry matter and lipid were significantly lower in fish fed diet GC-10 relative to those fed the control diet. Carcass composition was similar among treatments, although fish fed GC-10 exhibited significantly higher ash content. The results obtained in this study suggest that the inclusion of G. bursa-pastoris (GP) and U. rigida (UR), up to 10%, can be considered as very interesting ingredients in diets for sea bass juveniles, as no negative consequences on growth performance, nutrient utilization or body composition were observed. On the other hand, the inclusion of G. cornea (GC) should be limited to 5% of the diet.

Experimental integrated aquaculture of fish and red seaweeds in Northern Portugal

Three potentially valuable red seaweeds, Chondrus crispus Stackhouse, Gracilaria bursa pastoris (S.G. Gmelin) P.C. Silva and Palmaria palmata (L.) O. Kuntze, collected in northern Portugal, were cultivated using the nutrient-rich effluents from a local turbot ( Scophthalmus maximus Linnaeus) and sea bass ( Dicentrarchus labrax Linnaeus) farm. The algae were cultivated in a two level cascade system. Several arrangements of the cascade system, stocking densities (3, 5, 7 and 8 kg m − 2 ) and water fluxes (140 and 325 l h − 1 ) were tested to optimize biomass yield and nitrogen uptake rate and efficiency. The yield and the total ammonium nitrogen (TAN) uptake of the three species were highly seasonal. Palmaria could not survive culture conditions during the summer when water temperature was above 21 °C. In the spring, Palmaria had an average yield of 40.2 (± 12.80) g DW m − 2 day − 1 and a nitrogen uptake efficiency (NUE) of 41.0% (± 17.26%). NUE expresses, in percentage, the average reduction in TAN concentration between the inflows and the outflows of the tanks. Chondrus performed better in summer with an average yield of 37.0 (± 11.10) g DW m − 2 day − 1 and removing 41.3% (± 17.32%) of nitrogen. Gracilaria grew year round, but also performed better during spring/summer, producing an average of 29.1 (± 2.90) g DW m − 2 day − 1 , and only 7.3 (± 5.08) g DW m − 2 day − 1 during autumn. Yield of C. crispus did not differ significantly when grown at two different stocking densities (5 kg m − 2 and 8 kg m − 2 ). On the other hand, Gracilaria had significantly higher yields at 5 than at 7 kg m − 2 . Better NUE, on average 76.7% (± 22.13%), was also obtained with 5 kg m − 2 stocking density and only 63.8% (± 24.62%) with 7 kg m − 2 . The yield of Gracilaria increased significantly with the increase of water flux from 140 to 325 l h − 1 and more nitrogen was removed from the water. However, NUE decreased from 48.4% to 33.4% at 140 and 325 l h − 1 , respectively. Biofiltration was highly improved by a cascade system with a NUE as high as 83.5%.

Contribution of exotic species, environmental factors and spatial components to the macrophyte assemblages in a Mediterranean lagoon (Thau lagoon, Southern France)

In the Thau lagoon, located on the French Mediterranean Coast, more than 20% of the macrophyte species are introduced species, likely through shellfish farming. Their impact on local soft substrate macrophyte communities has not yet been evaluated. In this study, we estimate the relationship between introduced species and the assemblage of indigenous macrophytes. Exotic species, environmental factors, and spatial distribution of macrophytes were analyzed with redundancy analysis (RDA) and partial redundancy analysis. We used data from a spatial survey that provided macrophyte densities, environmental characteristics (depth, granulometry, porosity, organic matter, phosphorous and nitrogen concentrations in the sediments), and geographical coordinates of sampling sites. The result of RDA showed that the macrophyte community structure can be explained by pure effects of exotic species (7%), pure effect of environmental factors (18%), pure spatial distribution (11%), and interactions among the above-mentioned variables (20%). Three exotic species ( Dasya sessilis, Chrysymenia wrightii, and Griffithsia corallinoides) were found to have a significant effect on indigenous macrophytes distribution. C. wrightii co-occurring with Cladophora sp. and Radicilingua thysanorhizans, whereas G. corallinoides co-occurring with Cutleria multifida. Depth, porosity, total P and N and the granulometric fraction 0–2 μm were identified as the best environmental predictors. Polysiphonia elongata and Stictyosiphon adriaticus were found in the deepest sites, whereas Nanozostera noltii was correlated with shallow waters. The distribution of Cladosiphon mediterraneus, Gracilaria bursa-pastoris, and Dictyota dichotoma depended on freshwater inputs, whilst Rytiphlaea tinctoria and Halopithys incurva were related with marine water inflows. To further investigate the relationships between species and explanatory variables, logistic regression was used expressing the presence–absence of local species with variables identified during the RDA.

Seasonal variations in photosynthetic irradiance response curves of macrophytes from a Mediterranean coastal lagoon

The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Thau lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 °C, 982 μmol O 2 g −1 dw h −1 and 9.1 μmol O 2 g −1 dw h −1/μmol photons m −2 s −1, respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 °C, 583 μmol O 2 g −1 dw h −1 and 2.6 μmol O 2 g −1 dw h −1/μmol photons m −2 s −1 respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to R d (ranging 6.7–794 μmol O 2 g −1 dw h −1, respectively for Rytiphlaea tinctoria at 7 °C and for Dasya sessilis at 25 °C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of P/ I curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species ( Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others ( N. noltii, Zostera marina, Chaetomorpha linum).

Agar from the reproductive and vegetative stages of Gracilaria bursa-pastoris

Native agar was extracted from cystocarpic, tetrasporic and vegetative plants of Gracilaria bursa-pastoris and the agar yield, gel strength, gelling temperature, intrinsic viscosity and 3,6-anhydro- l-galactose and sulfate content were analyzed. The results showed no significant differences in the agar yield and intrinsic viscosities at different reproductive stages. The vegetative plants showed higher gel strength agars than the carposporic and tetrasporic plants, but their gelling temperature was lower. The gel strengths and gelling temperatures were explained by the sulfate and 3,6-anhydro- l-galactose contents of the specimens. On the whole, the quality of the agar varied as a function of the reproductive stages. These results suggest that harvesting should be avoided during the main period of the reproductive stage of this seaweed.