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  • Gracilaria  (36)
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  • 1
    ISSN: 1573-5176
    Keywords: agarose ; Gracilaria ; algae ; polysaccharide ; 13C-NMR ; agar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of nitrogen availability on the chemical structure of agar polymers isolated fromGracilaria verrucosa strain G-16 was ascertained by sequential solvent extraction and carbon 13 nuclear magnetic resonance (13C NMR) spectroscopy. Agar isolated fromG. verrucosa strain G-16 cultured under nitrogen limited conditions showed large non-polar components but produced spectra indicative of only minor amounts of methylation. These agars also produced spectra suggesting the presence of floridean starch. The nitrogen supplemented cultures ofG. verrucosa strain G-16 produced agars of a more polar nature (hot-water soluble) and contained little detectable starch. The data suggest that the higher gelling temperatures of agar from nitrogen limited plants is not due to markedly higher methylation. These data also suggest that nitrogen effects on agar content may not be as significant as previously thought.
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  • 2
    ISSN: 1573-5176
    Keywords: hemagglutinins ; Gracilaria ; sulphated polysaccharide ; carbohydrate specificity ; seaweed ; electrophoretic behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolation and characterisation of marine algal hemagglutinins or lectins are essential for their potential industrial application as specific carbohydrate affinity ligands. The phosphate buffer extract of the red alga, Gracilaria verrucosa (Huds.) Papenfuss (Gigartinales, Rhodophyta) from Japan is known to contain three different hemagglutinins. The extract of the alga collected in March 1993 from Kagawa Prefecture, Japan, was purified by ammonium sulphate fractionation, ion exchange and gel filtration chromatography. Using gel filtration, two peaks were obtained (hereafter Peak 1 and Peak 2) which differed in molecular size and hemagglutinating activity against horse erythrocytes. Peak 1 corresponded to the known high molecular weight hemagglutinin, H-GVH. Peak 2 contained large amounts of hexose and sulphate along with a small amount of protein. It had a low molecular weight (gel filtration) similar to that of two of the previously reported G.verrucosa hemagglutinins but differed in its electrophoretic behaviour. Peak 2 is therefore a fourth hemagglutinin. Its activity was not inhibited by any of the monosaccharides tested but by the complex glycoproteins such as asialofetuin and fetuin. It had no divalent cation requirement for hemagglutination. The properties of this novel hemagglutinin could prove useful in industrial applications.
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  • 3
    ISSN: 1573-5176
    Keywords: ecological engineering ; biofilter ; aquaculture ; seaweeds ; mariculture ; eutrophication ; Gracilaria ; shrimp farming ; mangroves ; ecological footprint
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rapid scale growth of intensive mariculture systems can often lead to adverse impacts on the environment. Intensive fish and shrimp farming, being defined as throughput-based systems, have a continuous or pulse release of nutrients that adds to coastal eutrophication. As an alternative treatment solution, seaweeds can be used to clean the dissolved part of this effluent. Two examples of successfully using seaweeds as biofilters in intensive mariculture systems are discussed in this paper. The first example shows that Gracilaria co-cultivated with salmon in a tank system reached production rates as high as 48.9 kg m−2 a−1, and could remove 50% of the dissolved ammonium released by the fish in winter, increasing to 90–95% in spring. In the second example, Gracilaria cultivated on ropes near a 22-t fish cage farm, had up to 40% higher growth rate (specific growth rate of 7% d−1) compared to controls. Extrapolation of the results showed that a 1 ha Gracilaria culture gave an annual harvest of 34 t (d. wt), and assimilated 6.5% of the released dissolved nitrogen. This production and assimilation was more than twice that of a Gracilaria monoculture. By integrating seaweeds with fish farming the nutrient assimilating capacity of an area increases. With increased carrying capacity it will be possible to increase salmon cage densities before risking negative environmental effects like eutrophication and toxic algal blooms sometimes associated with the release of dissolved nutrients. The potential for using mangroves and/or seaweeds as filters for wastes from intensive shrimp pond farming is also discussed. It is concluded that such techniques, based on ecological engineering, seems promising for mitigating environmental impacts from intensive mariculture; however, continued research on this type of solution is required.
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  • 4
    ISSN: 1573-5176
    Keywords: Chile ; interfertility trials ; Gracilaria ; ITS region ; morphotypes ; PCR ; RFLPs ; New Zealand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Restriction fragment length polymorphism (RFLP) patterns of the internal transcribed spacer (ITS) of the nuclear ribosomal cistron and crossability trials were used to characterize four morphotypes of Gracilaria from Lenga, Isla Santa María and Maullín, Chile, and two morphotypes from sites in New Zealand. PCR products from all Chilean morphotypes resulted in a major single band of ca. 1198 bp. ITS-RFLP profiles generated with the restriction enzymes Cla I, Hae III, Pst I, Hha I, Rsa I and Taq I, were identical in all cases. All crosses within, as well as between, morphotypes resulted in cystocarp differentiation, with the production of viable carpospores. Based upon these data, it is concluded that the four morphotypes from Chile correspond to a single species, G. chilensis, and that the ITS-RFLP pattern is a useful marker to predict genetic relatedness at the specific level in Gracilaria. A comparison of the ITS-RFLP patterns of the Chilean morphotypes with the patterns of two samples of G. chilensis from New Zealand revealed that the sample from Scorching Bay, Wellington, fits the Chilean ITS-RFLP patterns. The population from Blockhouse Bay, Auckland, appears to correspond to another species.
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  • 5
    ISSN: 1573-5176
    Keywords: agar ; Gracilaria ; polysaccharides ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 6
    ISSN: 1573-5176
    Keywords: Gracilaria ; strain selection ; growth ; photosynthesis ; rubisco ; agar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A strain selection procedure using Gracilaria verrucosa gametophytic sporelings was found to be an efficient tool for the improvement of Gracilaria strains. Two strains, C-2 and A-18, which were isolated and grown clonally, showed higher growth rates under high and low temperature conditions, respectively, than the local Gracilaria conferta. Growth rate, photosynthesis and chlorophyll, which were measured under different temperature and photon flux densities, demonstrated an overall advantage of the selected strains over the wild type strains of both G. verrucosa and G. conferta. Growth rates were also generally in positive correlation with the carboxylase activity of Rubisco. The G. verrucosa wild type also had a 40% higher agar content than G. conferta. The selected strains thus showed higher potential for outdoor cultivation than local wild type populations.
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  • 7
    ISSN: 1573-5176
    Keywords: decomposition ; Gracilaria ; nitrogen ; nutrients ; temperature ; Ulva
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study determined the rate at which nitrogen accumulated in seaweeds is released during decomposition and the effect of temperature on their rates of decomposition and nitrogen release. Gracilaria verrucosa and Ulva lactuca decomposed rapidly in outdoor mesocosms. Ulva, but not Gracilaria, became nitrogen-enriched during decomposition. Maximal weekly rates of nitrogen release were 5.91 ± 2.23 and 6.37 ± 2.59 g N m−2 d−1, respectively for Gracilaria and Ulva. Temperature had a significant effect on the decomposition rate of Gracilaria in a laboratory experiment: decomposition was greater at 30 °C than at 25 °C. No net decomposition was observed at 16 °C. Gracilaria became nitrogen enriched at 30 °C, but not at 16° or 25°. The release of stored nutrients from decaying seaweeds should be included in nutrient budgets and models when seaweed standing stocks are significant. Seaweed source-sink relationships are important ecologically and can be applied to attempts at using seaweeds as environmental monitors of anthropogenic eutrophication and to efforts of cultivating seaweeds for the improvement of water quality.
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  • 8
    ISSN: 1573-5176
    Keywords: brackish water ; co-cultivation ; epiphytes ; Gracilaria ; macroalgae ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pond cultivation of the subtropical, euryhaline macroscopic red algaGracilaria tenuisipitata var.liui Zhanget Xia was carried out in brackish seawater (6–7‰) in the Gryt archipelago on the east coast of Sweden, using four outdoor tanks of 30–40 m3. Growth rate and nutrient uptake in batch culture were measured with the aim of estimating the water purification capacity ofG. tenuisipitata in outdoor conditions. Its ability to withstand epiphytic infections was also studied. An average growth rate of 4‰ biomass increase per day was recorded during two seasons with a maximum growth rate of 9‰ d−1. The initial biomass was usually 1 kgFW m−3 (FW, fresh weight). The nutrient uptake capacity was on average ca. 1 g Ni kgFW−1 d−1 and 0.08 g Pi kgFW−1 d−1 and the uptake rates for NH4 +-N were higher than those for NO3 −-N. Both the growth rate and the nutrient uptake rate were highest at the highest water temperature. Co-cultivation with rainbow trout (Oncorhynchus mykiss) was tested: with trout fodder as the only nutrient inputG. tenuistipitata could grow and maintain low levels of Ni and Pi with optimum efficiency at a trout: alga ratio of 1:1 (w:w). Epiphytic growth of filamentous green and brown algae was limited, probably as a result of the high pH values caused by inorganic carbon uptake byG. tenuistipitata. The growth ofEnteromorpha intestinalis, the only significant epiphyte, was completely inhibited and the majority of plants died by a few days treatment with 100 µg 1−1 Cu2+, a concentration that did not severely affectG. tenuistipitata. We conclude thatG. tenuistipitata can be cultivated in outdoor ponds in southern Sweden during 5–6 months of the year using aerated or unaerated batch cultures and that wastewater from trout cultivation may be used as a nutrient source, resulting in purification with respect to N and P.
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  • 9
    ISSN: 1573-5176
    Keywords: light ; Gracilaria ; shape parameters ; velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Characteristic shape parameters, light intensities and relative water velocities were estimated in thalli of free-moving seaweeds, using threeGracilaria-like species:G. cornea, G. conferta andGracilariopsis lemaneiformis. Relative velocities over the branches were determined mostly by rotation of the algae in the water as opposed to linear translation. The tree major shape parameters of the thallus, weight, volumetric specific weight and areal specific weight, explain the differences in relative velocity. Relative velocities near the center of the thallus were about 50% to 80% of the external velocity. Light intensities at the vicinity of the center ofG. cornea ranged between 60% to 90% of the external light intensity. Light attenuation in the center was proportional to the weight of the thallus. The significance of light and velocity attenuation as a function of shape parameters is discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 7 (1995), S. 245-254 
    ISSN: 1573-5176
    Keywords: agar ; Gracilaria ; structure ; quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Agar polymers synthesized by species of the genus Gracilaria constitute a complex mixture of molecules, containing several extremes in structure. Sulphate hemi-esters, methyl ethers and pyruvic ketals can alter in a number of ways the structural regularity of agar based on strictly 3-O-linked β-l-galactopyranose and 4-O-linked α-l-galactopyranose residues. In comparison with agars from Gelidium and Pterocladia, agars from Gracilaria can have higher degrees of sulphation, methoxylation and pyruvylation. The gelling ability of agars from most of Gracilaria species is considerably improved by adopting, before extraction, an alkali pretreatment which converts α-l-galactose 6 sulphate into 3,6-anhydro-α-l-galactose. Native agars obtained from Gracilaria cannot be classified, with few exceptions, as bacteriological grade agar as they have a high content of methoxyls and consequently high gelling temperatures. On the contrary, the genus Gracilaria is considered the most important source of food and sugar-reactive grade agars. Among techniques which can be used to study algal polysaccharides, combined 1H and 13C nuclear magnetic resonance spectroscopy represent the most effective and powerful method for the investigation of the chemical structure of agarocolloids.
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