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August 10, 2007
Abstract
We investigated effects of the introduced Pacific oyster ( Crassostrea gigas ) on native eelgrass ( Zostera marina ) health on Cortes Island, British Columbia, Canada. Oysters physically alter their environment by increasing habitat complexity and altering water flow, and possibly by causing sulphide to accumulate in the sediment. Sulphide is toxic to eelgrass, and the current decline of eelgrass around Cortes Island may be a consequence of oyster population growth. While oysters and eelgrass coexist at a regional scale, eelgrass is typically absent directly seaward of oyster beds (the “below-oyster zone”) on Cortes Island. In a controlled experiment, we transplanted eelgrass plugs to below-oyster plots to determine whether this habitat is suitable for eelgrass growth. Shoot and leaf number were significantly greater over time in eelgrass-bed transplants than in below-oyster transplants. These results indicate that the below-oyster zone is unsuitable for eelgrass growth; if a causal link exists between oyster presence in the high intertidal zone and eelgrass absence directly seaward, then expansion of feral and farmed oyster beds will result in further eelgrass loss on Cortes Island.
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August 10, 2007
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Metal pollution in aquatic ecosystems can pose a major environmental concern impacting various life-forms. The usefulness of seaweeds as biomonitors or indicators of metals in the coastal bays of the Delmarva Peninsula is highlighted in this study, conducted in early spring 2006. Lack of any preexisting data on metal loads in Delmarva seaweeds and in the ambient medium (water and sediments) led to this pilot study for preliminary investigations on the ecological health of these coastal bays. The seaweed species collected from three different sites of the Delmarva Peninsula were: phaeophytes Fucus vesiculosus , and Fucus distichus , chlorophytes Ulva lactuca , and Enteromorpha intestinalis, and rhodophyte Gracilaria tikvahiae . The sampled seaweeds, seawater, and sediments were subsequently analyzed for chromium, manganese, cobalt, nickel, copper, lead, arsenic, and zinc. The results showed high concentrations of Mn, and low concentrations of Cu in almost all the species. Bioconcentration factors (BCFs) in Ulva lactuca and Fucus vesiculosus , across sites, were similar (though the orders of magnitude varied) for Cu, Zn, and Ni. Calculation of metal pollution index (MPI) and Tomlinson pollution load index (PLI) showed that all three sites had low contamination with the metals investigated.
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August 10, 2007
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This study characterized morphological variation in the kelp, Egregia menziesii , over a large geographic scale. Marked differences in rachis and lateral blade morphology were observed, suggesting local adaptation to the variable conditions of wave exposure and upwelling found across the study area. Observations of rachis type at different developmental stages indicated differential survivorship of smooth versus papillated individuals at sites with differing wave exposure. Variations in Egregia morphology have long been recognized and were previously used for discriminating species within the genus; thus, we tested the hypothesis that the different morphological forms reflect genetically distinct populations. Nucleotide sequences of the ITS regions did not reveal genetic structure among three, morphologically distinct populations providing little evidence for speciation in Egregia .
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August 10, 2007
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An improved staining method using carbol fuchsin was successfully adopted for chromosomes of marine algae, including Porphyra , Undaria pinnatifida and Saccharina japonica . The haploid numbers of P. haitanensis and P. yezoensis (observed clearly in vegetative, spermatangial and conchosporangial cells) were five and three, respectively. The diploid numbers of P. haitanensis and P. yezoensis (in immature conchosporangial cells) were ten and six, respectively. Pit connections between cells of conchosporangia and cell mashes were clearly differentiated. Chromosomes in conchocelis cells in prophase were clearly stained with the improved carbol fuchsin method. The chromosome number of gametophytes of S. japonica was 31, and that of U. pinnatifida was 30. Hydrolysis with 1 M HCl at 60°C for 7–8 min to produce a very transparent cytoplasm was necessary for staining chromosomes in conchosporangial branches of Porphyra . Iron alum acetocarmine, aceto-iron-hematoxylin-chloral hydrate and carbol fuchsin were used to stain the chromosomes of the vegetative cells, spermatangial cells and conchosporangial cells of Porphyra and the gametophytes of U. pinnatifida and S. japonica . Among the three methods, the carbol fuchsin method was simple and rapid, yielding deep staining of chromosomes and good contrast between the nucleus and cytoplasm.
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August 10, 2007
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The cultivars of Gracilaria lemaneiformis in Nanao (Guangdong province), Putian (Fujian) and Lianyungang (Jiangsu) all originate from the Qingdao (Shandong) wild population. After years of cultivation via vegetative propagation in marine farms in their new habitats, these cultivars vary in economic properties and morphological characters. In order to demonstrate whether the variations are caused by genetic variation or habitat shift, Gracilaria asiatica as an outgroup, the three cultivars, together with two morphologically different wild populations in Qingdao were characterized by RAPD markers and total soluble proteins. The results consistently showed that: (1) The Nanao cultivar, a selected strain enduring higher temperature, had the most variations. (2) The other two cultivars were closely related to one other. (3) The morphologically differentiated G . lemaneiformis populations in Qingdao were two separate populations. The results indicate that the use of RAPD markers is a powerful tool for exploring genetic relationships among G. lemaneiformis populations. Morphological and phenotypic variations of the cultivars are due to genetic changes rather than environmental changes. Years of artificial selection and asexual propagation have led to a reduction of intra-population genetic diversity in farmed populations and successive transplantation between farms has caused a reduction of inter-population genetic differentiation.
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August 10, 2007
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An invasive green alga, Caulerpa racemosa , collected from the South China Sea was tested for its antiviral properties. Hot water extracts and the n -butanol fraction obtained showed potent inhibition of herpes simplex virus type 1 (HSV-1) and Coxsackie virus B3 (Cox B3). A sulfoquinovosyldiacylglycerol (SQDG) compound was isolated and purified from the n -butanol fraction following further antiviral-guided fractionation. The SQDG compound exhibited an excellent antiviral effect against HSV-2, with a 50% inhibitory concentration (IC 50 ) of 15.6 μg ml -1 against both standard and clinical strains of HSV-2, but showed only moderate antiviral effects against HSV-1 and Cox B3. The SQDG compound was chemically characterized using spectroscopic methods as (2 S )-1,2-di- O -palmitoyl-3- O -(6′-sulfo-α-D-quinovopyranosyl) glycerol. This is the first isolation from C. racemosa of this SQDG compound with notable selective antiviral activity against HSV-2.
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August 10, 2007
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Agar from Gracilaria edulis collected in the Philippines is composed primarily of a repeating disaccharide unit of 4-linked 3,6-anhydro- α- L-galactopyranose (LA) and 3-linked 6- O -methyl- β- D-galactopyranose (G6M). Chemical and spectroscopic analyses further revealed partial (19–27 mol %) methylation at O-2 of the LA residues. Sulfate was attached to O-4 of G6M and/or G , with approximately 20% of these residues bearing the substituent. No pyruvate substituent was detected. A seasonal assessment of the composition, rheological and physical properties of Gracilaria edulis agar was undertaken. Constituent sugar analysis revealed a variable degree of methylation (80–91 mol % on O-6 of the G and 19–27 mol % on O-2 of the LA residues); the highest amounts of mono- O -methylated residues (G6M and LA2M) were found in the samples collected in the dry season while the lowest was obtained during the rainy season. The sample collected during the onset of the rainy season contained the lowest amount of sulfate (2.3%) while the cold season sample contained the highest sulfate content (3.2%). Seaweed samples collected during the onset of the rainy season exhibited the highest agar yield, gel strength, deformation, cohesiveness, and melting temperature. Gracilaria edulis agar possesses gel characteristics useful in the food industry.
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August 10, 2007