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October 13, 2005
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October 13, 2005
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October 13, 2005
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October 13, 2005
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June 1, 2005
Abstract
In three Gelidiella acerosa beds on the poorly-studied eastern coasts of the Philippines, cover and biomass of this commercially important agar-producing red alga were measured. The three selected G. acerosa beds represented low (mean cover < 5%), medium (approximately 10%) and high cover (> 20%) vegetation. In each of the sites, we estimated the cover of G. acerosa fronds within 10 x 10 cm grids (n ranged from 33–36) in various strata. All G. acerosa fronds within each grid were harvested, cleaned of attached epiphytes and sediments, and subsequently, oven-dried at 60 °C to constant weight. We applied regression analysis to establish empirical relationships between cover and biomass. All linear regression lines were highly significant (p < 0.001, R 2 > 0.6) indicating that biomass could be confidently estimated from cover estimates: low cover (y = 0.0171x + 0.310;R 2 = 0.67, p < 0.0001), medium cover (y = 0.0363x + 0.118, R 2 = 0.83, p < 0.0001) and high cover (y = 0.0304x + 0.481, R 2 = 0.80, p < 0.0001). Evidently though, sites with higher overall mean cover (also longer thalli) had significantly steeper regression slopes, which was most pronounced when comparing sites with the lowest (< 5%) and highest (> 20%) mean cover. Nevertheless, we subsequently projected a minimum annual yield from the known 51 ha along the eastern coasts amounting to, at a minimum, 23 t dw y −1 . Such yield may translate to approximately 68.8 million pesos (US$ 1.38 million) in gross sales of agar.
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June 1, 2005
Abstract
In the Gulf of California, marine organisms can be exposed to great fluctuations of environmental parameters that regulate their metabolism and survival. We evaluated over a two-year period the photosynthetic characteristics, growth rates and nitrate uptake rates as a function of irradiance and temperature in two rhodophytes, Chondracanthus squarrulosus and Eucheuma uncinatum , endemic to the Gulf of California. In the field, plants were exposed to an annual temperature and irradiance variation of more than 14 °C and 30 mol quanta m −2 d −1 , respectively. Maximum cover of C. squarrulosus in the field occurred during the winter-spring while maximum values for E. uncinatum occurred during the summer-fall. Maximum photosynthesis (P max ) values were approximately two- to three-fold greater in C. squarrulosus than in E. uncinatum , and were out of phase in the two species by approximately three months. The greater P max values found for C. squarrulosus than E. uncinatum are consistent with its two-fold greater cover and growth rates in the field. Photosynthetic efficiency of C. squarrulosus decreased as temperature increased, while it remained relatively constant in E. uncinatum throughout a wide range of assayed temperature suggesting a photosynthetic advantage for C. squarrulosus over E. uncinatum during the colder/less illuminated months of the year.
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June 1, 2005
Abstract
Patch distribution and small-scale ( i.e. , within-patch) temporal variability in plant morphology, biomass, shoot density, tissue nutrient content and growth were studied in the intertidal seagrass Zostera noltii at Los Toruāos salt-marsh (Cádiz, Spain). The area covered by Z. noltii was 7.3%, and decreased exponentially with depth. The lack of recruitment from seedlings largely explained the normal patch size distribution observed. Overall, lower biomass, shoot density, above-ground to below-ground biomass ratios and higher leaf elongation rates were recorded at the patch edge, where biomass dynamics were primarily controlled by recruitment and mortality processes. In contrast, temporal variation in above-ground biomass in the patch centre depended largely on changes in shoot leaf number and size. There was no correlation between total biomass and shoot density in the patch centre suggesting that below-ground biomass may be space-limited. Low aboveground biomass and shoot elongation rates were recorded in May, regardless of position within the patch, and were coincident with the abundance of Ulva sp. mats. Light reduction by Ulva canopies also resulted in a mobilization of carbohydrate reserves. Such resource reallocation may represent an important short-term survival strategy, maintaining leaf and rhizome elongation capacity.
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June 1, 2005
Abstract
The frequency of Posidonia oceanica past flowering events in a north-western Mediterranean area was examined using a reconstructive age technique. We also investigated possible relationships among shoot age and occurrence of flowering. Seven flowering events were recorded over the 14-year period examined. Considerable variations in inflorescence frequency occurred among years (0–25.3%), with two years of abundant flowering (1989 and 1993) separated by several years with little or no flowering. Only 2% of the shoots sampled flowered twice; contrary to previous opinion, the interval among two successive flowerings was considerably shorter than 10 years, varying from 1 to 4 years. The minimum reproductive age of shoots was 6 months. The probability of flowering increased with age until 6 years of age, and decreased thereafter. Both the number of leaves and rhizome segments produced by a shoot during a flowering year did not differ significantly from those produced in the years preceding and following a flowering event, suggesting that the cost of flowering could not affect short-term growth of shoots. On the basis of our results we can speculate that the maximum sexual reproductive output for P. oceanica in the area studied was about 340–460 seeds m −2 in 1994.
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June 1, 2005
Abstract
Vaucheria karachiensis sp.nov. is reported from the mangrove habitat of Karachi, Pakistan. It grows abundantly as an epiphyte on the pneumatophores of the mangrove Avicennia marina where it forms a compact mass surrounding them. It is characterized by its epiphytic habit, the presence of septa in filaments other than at the base of reproductive bodies, the very large size of its smooth antheridia and its monoecious habit.
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June 1, 2005
Abstract
Hypnea cornuta (Kützing) J. Agardh var. stellulifera J. Agardh (Hypneaceae, Gigartinales) is distinguished from the type variety by the short, thick, rigid axes that produce thick adventitious branchlets as well as the tetrasporangial sori and spermatangial sori that extend to the parental axis and branches. Var. stellulifera is raised to the rank of species as Hypnea stellulifera (J. Agardh) Yamagishi et Masuda on the basis of these morphological differences and comparative chloroplast-encoded rbc L sequences. Reproductive structures of Heterosiphonia crispella (C. Agardh) Wynne (Dasyaceae, Ceramiales), which is referable to var. laxa (Borgesen) Wynne, are described. Two species of Laurencia (Rhodomelaceae, Ceramiales) are reported from Malaysia for the first time: L. pygmaea Weber-van Bosse and L. majuscula (Harvey) Lucas. Critical features of L. pygmaea include four pericentral cells per segment, the presence of a single (rarely two) corps en cerise per superficial cortical cell, and the production of a single tetrasporangium-bearing pericentral cell on each fertile segment.
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June 1, 2005
Abstract
The occurrence of the Mediterranean red alga Ceramium giacconei Cormaci et Furnari, in the northeastern Pacific Ocean (Gulf of California) is reported for the first time, associated with a rhodolith bed. Although C. giacconei is similar to C. cingulatum Weber-van Bosse, known from the Indian Ocean, our observations confirm the validity of C. giacconei as a distinctive species on the basis of the following features: 1) erect thallus markedly compressed above several basal segments, 2) complete cortication except the basal segments, 3) unequal development of corticating filaments, 4) oblong axial cells, 5) solitary and straight apex, 6) tetrasporangia immersed in cortex and produced from both periaxial and cortical cells, 7) spermatangia produced from cortical cells, 8) cystocarps surrounded by 4 or 5 involucral branches. Sexual reproductive structures are described for the first time and conform to previous reports of the genus.
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June 1, 2005
Abstract
Nitrogen (δ 15 N) and carbon (δ 13 C) isotopic compositions of Posidonia oceanica were determined during three seasons along a bathymetric gradient (4–38m depth).The δ 15 N values are low (2.2±0.9 ‰ ) and variable. They do not show any relation to depth or sampling dates. There is a significant difference between the δ 15 N values of the youngest and the oldest leaves, probably as a result of N resorption and senescing during leaf ageing. The δ 13 C values of young Posidonia leaves vary with depth, showing the relationship between δ 13 C values and primary productivity rate, and the use of a bicarbonate/CO 2 mixture as an inorganic carbon source. The δ 13 C values of the oldest P. oceanica leaves are depleted in 13 C compared to those of young leaves. This modification of the 13 C signatures in relation to leaf age is particularly important between 20 and 29 m depth. This modification could be related to photosynthetic rate change during ageing, but also to change in carbohydrate composition and content.
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June 1, 2005
Abstract
The proximate composition, mineral and trace metal contents were determined for three different algal raw materials: attached Sargassum mangarevense , Turbinaria ornata and drift algae (almost entirely composed of these two species). Dietary fibre (38.1–42.8% dw) and ash (30.6–39.8% dw) were the most abundant constituents in all samples.A high protein content (13.2±1.9% dw) was found in S. mangarevense . All algae displayed similar amino acid patterns with a predominance of aspartic and glutamic acids (28.10–33.77% of total amino acids). Attached specimens had similar compositions of fatty acids, with a high concentration of polyunsaturated forms, especially C 18 and C 20 . All samples showed a high mineral content, particularly in calcium, magnesium, potassium ( T. ornata ), iodine ( S. mangarevense ), iron and zinc. The drift algae usually accumulated more minerals than the attached algae. The potential use of both attached and drift algae as fertilisers, animal food and cosmetic products is discussed.
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June 1, 2005
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The polysaccharides from six New Zealand species of red seaweed were examined by 13 C NMR spectroscopy, and found to have the following structures: Caulacanthus ustulatis (Caulacanthaceae): 3:1 κ/ι-hybrid carrageenan; Craspedocarpus erosus (Cystocloniaceae): ι-carrageenan; Callophyllis hombroniana (Kallymeniaceae): θ-carrageenan together with minor components including up to 10% pyruvylation, and 4-linked D-and L-galactose; Gracilaria truncata (Gracilariales) (two new samples): agar, agar with 45 % 6- O -methylation on the 3-linked unit; Capreolia implexa (Gelidiales): agar with 10% 6- O -methylation on the 3-linked unit and 6% 2- O -methylation on the anhydrogalactosyl unit; Gymnogongrus torulosus : 1:1.15 κ/ι-hybrid carrageenan with precursors. The 13 C NMR spectra of the two precursors are very similar to each other. The set of plants termed Gracilaria truncata may include more than one species.
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June 1, 2005
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July 27, 2005
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