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- Andreasson, Kristin I. M., 1963, et al.
(författare)
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Biological weighting functions as a tool for evaluating two ways to measure UVB radiation inhibition on photosynthesis
- 2006
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Ingår i: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 84:2, s. 111-118
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Tidskriftsartikel (refereegranskat)abstract
- To estimate the inhibitory effect of the changing UVB radiation (UVBR, 280-315 nm) on earth's ecosystems, an understanding of its wavelength dependency is needed. The tool used for these estimations is the biological weighting function (BWF), whereby the inhibition of different wavelengths is calculated. B\WFs were determined for three algae species from different classes, Phaeodactylum tricornutum (Bacillariophyceae), Dunaliella tertiolecta (Chlorophyceae) and Rhodomonas sp. (Cryptophyceae), using polychromatic irradiation, where the UVBR spectra were varied with cut-off filters. For each alga, BWFs were determined for two photosynthetic parameters; the quantum yield measured as fluorescence from Photo System II in a pulse-amplitude-modulation (PAM) fluorometer, and the fixation of C-14-labelled carbon dioxide. The BWFs were calculated with the Rundel method, using the radiation data between 270 and 360 nm with 1 nm resolution. The results show that the UVBR damages were generally higher when using the carbon fixation measurements than when measuring with the PAM technique. When using PAM, P. tricornutum in particular had a sensitivity intermediate between the sensitive Rhodomonas sp. and the more tolerant D. tertiolecta, but was as sensitive as, or even more sensitive, than Rhodomonas sp. when using carbon fixation. D. tertiolecta was shown to be less sensitive when using both techniques and the inhibition of its photosynthesis was almost as high when using PAM as when using carbon fixation. We concluded that, although the PAM technique has advantages such as being cleaner and easier to use, it is unable to Substitute the carbon fixation measurements. Not only are the algae less sensitive when measured with PAM than they are when measured as carbon fixation, the relationship between the effects on the algae measured with the two techniques also differs. As fixation of carbon dioxide integrates a larger part of the photosynthetic machinery, it should be favoured as a measure of photosynthesis. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
- Andreasson, Kristin I. M., 1963, et al.
(författare)
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Reduction in growth rate in Phaeodactylum tricornutum (Bacillarlophyceae) and Dunaliella tertiolecta (Chlorophyceae) induced by UV-B radiation
- 2007
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Ingår i: Journal of Photochemistry and Photobiology B-Biology. - : Elsevier BV. - 1011-1344. ; 86:3, s. 227-233
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Tidskriftsartikel (refereegranskat)abstract
- The effect of UV-B radiation (UVBR, 280-315 nm) on growth rate during 72 h of incubation, was measured for two marine microalgae - Dunaliella tertiolecta (Chlorophyceae) and Phaeodactyhan tricornutum (Bacillariophyceae). The resulting inhibition of growth rate was analysed by calculating biological weighting functions (BWFs). The growth rate of D. tertiolecta was slightly more inhibited by UVBR (over the whole range of the spectrum) than was the growth rate of P. tricornutum, but the wavelength dependencies were the same. Our results were compared with results from photosynthesis experiments of Andreasson and Wangberg [1], where two methods, pulse amplitude modulation (PAM) fluorescence and carbon fixation, were measured for these same algae. The BWF for the growth rate, here, showed more wavelength dependency than the BWF for the previous two photosynthesis measurements - except for the carbon fixation BWF in P. tricornutum, which was closer to the BWF for growth rate. The wavelength dependency of the growth rate inhibition showed less variation between the species than the inhibition of the photosynthesis. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Leu, E., et al.
(författare)
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Effects of changes in ambient PAR and UV radiation on the nutritional quality of an Arctic diatom (Thalassiosira antaretica var. borealis)
- 2006
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 337:1, s. 65-81
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Tidskriftsartikel (refereegranskat)abstract
- Polyunsaturated fatty acids (PUFAs) are essential macromolecules that are synthesized by phytoplankton during spring bloom, and they play a key role in the Arctic food web. They are, however, considered to be sensitive to oxidation by UV radiation (280-400 nm). Changes in the food quality of primary producers may affect the transport of biomass and energy in the whole ecosystem. Using a common Arctic diatom, we looked at the effect of ambient and increased UV radiation on its nutritional quality, specifically, the fatty acid composition and elemental ratios. In May 2004, in the archipelago of Svalbard (79 degrees N), a unialgal culture of Thalassiosira antarctica var. borealis was subjected to a 17-day experiment in outdoor aquaria. The diatoms were kept in semi-continuous culture (40 1) and exposed to three treatments with different levels of UV radiation: none (UV-shielded), ambient, and enhanced. Fatty acid composition, C:N:P ratios, photosynthetic pigment composition, optimum quantum yield of PSII, and cell numbers were analysed over the experimental period. An initial increase in PAR (photosynthetically active radiation, 400-700 nm) intensities profoundly affected the fatty acid composition and substantially inhibited the synthesis of PUFAs, but the relative amounts of PUFAs were not reduced by UV radiation. Enhanced UV radiation did, however, cause a significant reduction in optimum quantum yield of PSII and affected some fatty acids, mainly 18:0 and 16:1 n-7, during the first week of the experiment. Both ambient and enhanced UV radiation caused significantly lower C:P and N:P ratios. At the same time, these treatments elicited a higher relative content of the photoprotective pigments diadinoxanthin and diatoxanthin. After acclimation to the new light levels these effects faded off. Thus, brief periods with high light exposure may cause significant changes in photosynthetic activity and food quality, but the capacity for photo-acclimation seems high. The impact of UV radiation seems to be less important for food quality than that of PAR during a sudden rise in total light intensity. (c) 2006 Elsevier B.V. All rights reserved.
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| 4. |
- Rothschild, Miriam, et al.
(författare)
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Cannabis sativa: volatile compounds from pollen and entire male and female plants of two variants, Northern Lights and Hawaian Indica
- 2005
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Ingår i: Botanical Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4074 .- 1095-8339. ; 147:4, s. 387-397
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Tidskriftsartikel (refereegranskat)abstract
- Sixty-eight compounds were identified by coupled gas chromatography and mass spectrometry (GC-MS) in the chemosphere of Cannabis sativa L. pollen and entire male and female plants of two cultivated varieties, Northern Lights and Hawaian Indica. Twenty-one and 28 substances, respectively, were present in pollen of the two forms. To conserve the natural composition of volatiles a delicate headspace method was employed. The two varieties represent different chemotypes which distinguish themselves, in the main quantitatively, in the setup of volatiles from pollen and entire male and female plants. Twenty compounds were monoterpenes, including the five major components: beta-myrcene (E)-beta-ocimene, terpinolene, beta-pinene and limonene; 25 were sesquiterpenes, and the other 23 were of mixed biogenetic origin, including 3-methyl-1-butanol and benzylalcohol which occurred only in pollen; two pyrazines occurred only in Northern Lights females. Besides being of interest in natural products chemistry, the results should have relevance for plant systematics and for the pharmaceutical and technical applications of Cannabis. We demonstrate that the pollen has a distinct chemical character in possessing two exclusive volatiles, while lacking seven compounds occurring in males and females of both variants. (c) 2005 The Linnean Society of London, Botanical Journal of the Linnean Society.
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| 5. |
- Taylor, Rebecca L, et al.
(författare)
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SEASONAL VARIABILITY IN POLYUNSATURATED ALDEHYDE PRODUCTION POTENTIAL AMONG STRAINS OF SKELETONEMA MARINOI (BACILLARIOPHYCEAE)
- 2009
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 45:1, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- The cosmopolitan bloom-forming diatom Skeletonema marinoi Sarno et Zingone is known to produce toxic polyunsaturated aldehydes (PUAs) in response to cell damage that can affect a diverse suite of organisms, including grazing species and competitor plankton species. The production of PUAs in nine different S. marinoi strains isolated at three different times of the year (spring, summer, and autumn) was assessed in relation to the predominant conditions at the time of isolation from Gullmar Fjord, Skagerrak. During the initial stages of growth, PUA production potential of S. marinoi was generally the highest in summer strains, although there was a substantial variation among strains isolated at the same time. Spring strains, however, showed a strong capacity for increased PUA production potential in later stage cultures with diminishing nutrient levels, reaching amounts similar to those observed in summer strains. In contrast, PUA production potentials of summer and autumn strains did not change significantly from the original values. There is negligible grazing pressure during the spring bloom in Gullmar Fjord, but a potential for high competition for resources, such as nutrients, toward the later stages of the bloom. In contrast, grazing pressure is much greater during summer and autumn, and there may also be nutrient limitation at this time. The PUA production potentials of S. marinoi appear to reflect the ecological conditions at the time of isolation with higher production potentials in strains isolated when conditions were likely to be less beneficial for survival.
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| 9. |
- Wängberg, Sten-Åke, 1955, et al.
(författare)
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Inhibition of primary production by UV-B radiation in an arctic bay - model calculations
- 2006
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Ingår i: Aquatic Sciences. - : Springer Science and Business Media LLC. - 1015-1621 .- 1420-9055. ; 68:2, s. 117-128
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Tidskriftsartikel (refereegranskat)abstract
- Inhibition of primary production by UV-B radiation (UVBR) in Kings Bay, western Spitsbergen, was modelled using measured physical and biological data. The underwater radiation regime was modelled using continuous measurements of incoming radiation and repeated measurements of underwater attenuation of Photosynthetic Active Radiation (PAR) and UVBR. By using attenuation measurements, P/I curves and UVBR sensitivity measurements, we modelled the reduction of primary production in the photic zone for 14 days. We also calculated how the estimate was dependent on the different factors. The model showed that, on average, 2.9 % of the primary production was inhibited by UVBR, assuming that the inhibition is a function of the UVBR irradiance. If the ozone layer were reduced to 200 DU, the inhibition would increase to 4.4% using unweighted UVBR values. The model indicated that at ambient ozone levels the inhibition was practically independent of the chosen weighting function, but the choice was critical when predicting the effects of a depleted ozone layer. At 200 DU, using DNA weighting, the inhibition was 14.4% but using erythema weighting it was 6.5%. Different P/I curves did not change the estimate while changes in water attenuation gave results in the range 1.6-5.2%. The most uncertain factor in the model was the estimate of the sensitivity of primary production. Using four different in situ incubations, the estimated integrated reduction in primary production caused by UVBR ranged from 0.05-4.1%.
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| 10. |
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