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11.
This study examined the roles of seasonal blooms of green algae, Ulva expansa (Setchell) Setchell et Gardner, and biotic disturbance by burrowing ghost shrimp, Callianassa gigas Dana, and foraging rays, on the intertidal distributions of a phoronid, Phoronopsis viridis Hilton, and a tellinid bivalve, Macoma nasuta (Conrad). Algal removal experiments in 1984 and 1986 demonstrated that heavy seasonal algal cover in the lower zone significantly reduced the abundances of both Phoronopsis and Macoma. Growth of Macoma transplanted into the algal zone was significantly lower in plots with algal cover than in plots regularly cleared of algae. Algal cover did not significantly affect early recruitment of either Phoronopsis or Macoma. Neither ghost shrimp nor rays appeared to reduce the abundances of phoronids or clams, although ray disturbance did result in a significant increase in the proportion of phoronids regenerating dorsal body parts. These results indicate that seasonal algal blooms are capable of producing discrete patterns of infaunal distribution in intertidal sedimentary habitats. 相似文献
12.
Y. B. Ho 《Hydrobiologia》1981,77(1):43-47
The amounts of tissue nitrogen, phosphorus, potassium, sodium, calcium and iron were estimated in the green alga Ulva lactuca L. collected from 9 rural and 14 urban littoral sites in the waters around Hong Kong Island during 1978 and 1979. The mean levels of tissue nitrogen and phosphorus were respectively 65% and 87% more in urban sites than in rural ones. Very significant correlation (r = 0.920) was found between the logarithmic concentration of seawater inorganic nitrogen and that of tissue nitrogen. The same applied to soluble reactive phosphorus in seawater and tissue phosphorus (r = 0.886). The levels of potassium, sodium and calcium in the alga were relatively uniform. However considerable variation in the level of iron was detected. The potential use of Ulva as an indicator species for eutrophication is discussed. 相似文献
13.
Mark Olischläger Inka Bartsch Lars Gutow Christian Wiencke 《Phycological Research》2013,61(3):180-190
Rising atmospheric CO2‐concentrations will have severe consequences for a variety of biological processes. We investigated the responses of the green alga Ulva lactuca (Linnaeus) to rising CO2‐concentrations in a rockpool scenario. U. lactuca was cultured under aeration with air containing either preindustrial pCO2 (280 μatm) or the pCO2 predicted by the end of the 21st century (700 μatm) for 31 days. We addressed the following question: Will elevated CO2‐concentrations affect photosynthesis (net photosynthesis, maximum relative electron transport rate (rETR(max)), maximum quantum yield (Fv/Fm), pigment composition) and growth of U. lactuca in rockpools with limited water exchange? Two phases of the experiment were distinguished: In the initial phase (day 1–4) the Seawater Carbonate System (SWCS) of the culture medium could be adjusted to the selected atmospheric pCO2 condition by continuous aeration with target pCO2 values. In the second phase (day 4–31) the SWCS was largely determined by the metabolism of the growing U. lactuca biomass. In the initial phase, Fv/Fm and rETR(max) were only slightly elevated at high CO2‐concentrations, whereas growth was significantly enhanced. After 31 days the Chl a content of the thalli was significantly lower under future conditions and the photosynthesis of thalli grown under preindustrial conditions was not dependent on external carbonic anhydrase. Biomass increased significantly at high CO2‐concentrations. At low CO2‐concentrations most adult thalli disintegrated between day 14 and 21, whereas at high CO2‐concentrations most thalli remained integer until day 31. Thallus disintegration at low CO2‐concentrations was mirrored by a drastic decline in seawater dissolved inorganic carbon and HCO3?. Accordingly, the SWCS differed significantly between the treatments. Our results indicated a slight enhancement of photosynthetic performance and significantly elevated growth of U. lactuca at future CO2‐concentrations. The accelerated thallus disintegration at high CO2‐concentrations under conditions of limited water exchange indicates additional CO2 effects on the life cycle of U. lactuca when living in rockpools. 相似文献
14.
《African Journal of Aquatic Science》2013,38(3):331-337
The effect of various macroalgal diets on the growth of grow-out (>20 mm shell length) South African abalone Haliotis midae was investigated on a commercial abalone farm. The experiment consisted of four treatments: fresh kelp blades (Ecklonia maxima (Osbeck) Papenfuss) (c. 10% protein); farmed, protein-enriched Ulva lactuca Linnaeus (c. 26% protein) grown in aquaculture effluent; wild U. lactuca (c. 20% protein); and a combination diet of kelp blades + farmed U. lactuca. Abalone grew best on the combination diet (0.423 ± 0.02% weight d?1 SGR [specific growth rate]; 59.593 ± 0.02 ?m d?1 DISL [daily increment in shell length]; 1.093 final CF [condition factor]) followed by the kelp only diet (0.367 ± 0.02% weight d?1 SGR; 53.148 ± 0.02 ?m d?1 DISL; 1.047 final CF), then the farmed, protein-enriched U. lactuca only diet (0.290 ± 0.02% weight d?1 SGR; 42.988 ± 0.03 um d”1 DISL; 1.013 final CF) that in turn outperformed the wild U. lactuca only diet (-0.079 ± 0.01% weight d?1 SGR; 3.745 ± 0.02 ?m d”?1 DISL; 0.812 final CF). The results suggest that protein alone could not have accounted for the differences produced by the varieties of U. lactuca and that the gross energy content is probably important. 相似文献
15.
Jihae Park 《Journal of phycology》2020,56(2):549-557
The physiological and biochemical changes in the green macroalga Ulva pertusa during the progression of sporulation have been characterized. The transition from the vegetative to the sporulation stage was accompanied by an increase in chlorophyll a (Chl a), chlorophyll b (Chl b), and carotenoid content, as well as an increase in DPPH scavenging and responsiveness to diphenylamine. However, oxygen evolution and maximum electron transport rate decreased. The discrepancy between photosynthetic performance and pigment content might relate to the self-shading of spores within a sporangium. Spore-forming U. pertusa thalli were low-light-adapted, due to an increase in the number of photosynthetic units. Decreased electron transport during sporulation might trigger sporulation, as for some cyanobacteria and other Ulva spp., via oxidization of the plastoquinone pool and cyclic phosphorylation, thus producing ATP to generate carbon and nitrogen skeletons required for spores. It is thus concluded that carotenoids function both in spore initiation and/or maturation and in their photoprotection. 相似文献
16.
Fouling species produce adhesive polymers during the settlement, adhesion and colonization of new surfaces in the marine environment. The present paper tests the hypothesis that enzymes of the appropriate specificity may prevent biofouling by hydrolysing these adhesive polymers. Seventeen commercially available enzyme preparations designed originally for bulk use in a range of end-use applications were tested for their effects on the settlement and/or adhesion of three major fouling species, viz. the green alga Ulva linza, the diatom Navicula perminuta and the barnacle Balanus amphitrite. The serine-proteases were found to have the broadest antifouling potential reducing the adhesion strength of spores and sporelings of U. linza, cells of N. perminuta and inhibiting settlement of cypris larvae of B. amphitrite. Mode-of-action studies on the serine-protease, Alcalase, indicated that this enzyme reduced adhesion of U. linza in a concentration-dependent manner, that spores of the species could recover their adhesive strength if the enzyme was removed and that the adhesive of U. linza and juvenile cement of B. amphitrite became progressively less sensitive to hydrolysis as they cured. 相似文献
17.
Isabel Thome Michala E. Pettitt Maureen E. Callow James A. Callow Michael Grunze Axel Rosenhahn 《Biofouling》2013,29(5):501-510
Conditioning, ie the adsorption of proteins and other macromolecules, is the first process that occurs in the natural environment once a surface is immersed in seawater, but no information is available either regarding the conditioning of surfaces by artificial seawater or whether conditioning affects data obtained from laboratory assays. A range of self-assembled monolayers (SAMs) with different chemical terminations was used to investigate the time-dependent formation of conditioning layers in commercial and self-prepared artificial seawaters. Subsequently, these results were compared with conditioning by solutions in which zoospores of the green alga Ulva linza had been swimming. Spectral ellipsometry and contact angle measurements as well as infrared reflection absorption spectroscopy (IRRAS) were used to reveal the thickness and chemical composition of the conditioning layers. The extent that surface preconditioning affected the settlement of zoospores of U. linza was also investigated. The results showed that in standard spore settlement bioassays (45–60 min), the influence of a molecular conditioning layer is likely to be small, although more substantial effects are possible at longer settlement times. 相似文献
18.
Elisa Martinelli Marianna Suffredini Antonella Glisenti Michala E. Pettitt Maureen E. Callow 《Biofouling》2013,29(5):529-541
Amphiphilic diblock copolymers, Sz6 and Sz12, consisting of a poly(dimethylsiloxane) block (average degree of polymerisation = 132) and a PEGylated-fluoroalkyl modified polystyrene block (Sz, average degree of polymerisation = 6, 12) were prepared by atom transfer radical polymerization (ATRP). Coatings were obtained from blends of either block copolymer (1–10 wt%) with a poly(dimethylsiloxane) (PDMS) matrix. The coating surface presented a simultaneous hydrophobic and lipophobic character, owing to the strong surface segregation of the lowest surface energy fluoroalkyl chains of the block copolymer. Surface chemical composition and wettability of the films were affected by exposure to water. Block copolymer Sz6 was also blended with PDMS and a 0.1 wt% amount of multiwall carbon nanotubes (CNT). The excellent fouling-release (FR) properties of these new coatings against the macroalga Ulva linza essentially resulted from the inclusion of the amphiphilic block copolymer, while the addition of CNT did not appear to improve the FR properties. 相似文献
19.
The vegetative growth of Ulva lactuca was studied to determine if the growth rate of the alga is driven by infradian rhythmicity. The influence of temperature on the infradian rhythm of growth was also investigated. Discs of Ulva were grown in controlled laboratory conditions at different combinations of temperature (5, 10, 15, 20°С) and irradiance (40 and 60 μmol photons m?2 s?1) under 12 : 12 h light : dark cycles. The growth rates exhibited a rhythmic pattern with one major peak every 2 or 3 days. Growth at 5 or 10°С increased the prevalence of 3-day cycles and maintained U. lactuca in the vegetative growth stage. In contrast, growth at 15 or 20°С provoked a predominance of the 2-day cycle and induced reproduction. The 2- or 3-day cycles were combined in longer cycles having a period close to 6 days. We suppose that the 2-, 3- and 6-day rhythms of physiological processes are related to large-scale Rossby and Kelvin waves, which produce oscillations in the geomagnetic field and seawater temperature with the same periods. The predominance of 2-day or 3-day fluctuations of the geomagnetic field and temperature probably determine the prevalence of reproduction and vegetative growth, respectively, in Ulva. 相似文献
20.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2186-2188
Present address: Hagoromo Foods Corporation. 151, Shimazaki-cho, Shimizu-shi, Shizuoka 424-85. Japan.The seasonal variation offatty acid composition in lipids of various organs and stomach contents of bonito (Euthynnus pelamis) was investigated. Although docosahexaenoic acid in the lipids of the stomach contents originating from their prey organisms varied from about 13% to 31%, it was the dominant unsaturated fatty acid andaccounted for more than 25% of the total fatty acids in the lipids of every organ of bonito in and out of season, and its seasonal variation was comparatively small. 相似文献