| 1. |
- Björn, Lars Olof, et al.
(författare)
-
Technical discussion I - Underwater light measurement and light absorption by algae
- 1996
-
Ingår i: Scientia Marina. - 0214-8358. ; 60:Suppl.1, s. 293-297
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper concepts and nomenclature of light measurements are discussed. The particular problems of underwater light measurements and the calibration of the equipment were presented. The pros and cons with spectroradiometers and broad band sensors were discussed. The use of specific ultraviolet-B sources for algal photobiology is recommended.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Roleda, Michael Y., et al.
(författare)
-
Photosynthetic performance, DNA damage and repair in gametes of the endemic Antarctic brown alga Ascoseira mirabilis exposed to ultraviolet radiation
- 2007
-
Ingår i: Austral Ecology. - : Wiley. - 1442-9985 .- 1442-9993. ; 32:8, s. 917-926
-
Tidskriftsartikel (refereegranskat)abstract
- Stress physiology on the reproductive cells of Antarctic macroalgae remained unstudied. Ascoseira mirabilis is endemic to the Antarctic region, an isolated ecosystem exposed to extreme environmental conditions. Moreover, stratospheric ozone depletion leads to increasing ultraviolet radiation (280-400 nm) at the earth's surface, thus it is necessary to investigate the capacity of reproductive cells to cope with different UV irradiances. This study is aimed to investigate the impact of exposure to different spectral irradiance on the photosynthetic performance, DNA damage and gamete morphology of the A. mirabilis. Gametangia, gametes and zygotes of the upper sublittoral brown alga A. mirabilis were exposed to photosynthetically active radiation (PAR = P; 400-700 nm), P + UV-A radiation (UV-A, 320-400 nm) and P + UV-A + UV-B radiation (UV-B, 280-320 nm). Rapid photosynthesis versus irradiance curves of freshly released propagules were measured. Photosynthetic efficiencies and DNA damage (in terms of cyclobutane pyrimidine dimers) were determined after 1, 2, 4 and 8 h exposure as well as after 2 days of recovery in dim white light. Saturation irradiance (I-k) in freshly released propagules was 52 mu mol photons m(-2) s(-1). Exposure for 1 h under 22 mu mol photons m(-2) s(-1) of PAR significantly reduced the optimum quantum yield (F-v/F-m), suggesting that propagules are low light adapted. Furthermore, UVR significantly contributed to the photoinhibition of photosynthesis. Increasing dose as a function of exposure time additionally exacerbated the effects of different light treatments. The amount of DNA damage increased with the UV-B dose but an efficient repair mechanism was observed in gametes pre-exposed to a dose lower than 5.8 x 10(3) J m(-2) of UV-B. The results of this study demonstrate the negative impact of UV-B radiation. However, gametes of A. mirabilis are capable of photosynthetic recovery and DNA repair when the stress factor is removed. This capacity was observed to be dependent on the fitness of the parental sporophyte.
|
|
| 5. |
|
|
| 6. |
- Roleda, Michael Y., et al.
(författare)
-
Susceptibility of spores of different ploidy levels from Antarctic Gigartina skottsbergii (Gigartinales, Rhodophyta) to ultraviolet radiation
- 2008
-
Ingår i: Phycologia. - 0031-8884. ; 47:4, s. 361-370
-
Tidskriftsartikel (refereegranskat)abstract
- Haploid tetraspores and diploid carpospores from Antarctic Gigartina skottsbergii were exposed in the laboratory to photosynthetically active radiation (400-700 nm = P), P + ultraviolet (UV)-A radiation (320-700 nm = PA) and P + UV-A + UV-B radiation (280-700 nm = PAB). Photosynthetic performance, DNA damage and repair, spore mortality, and an initial characterization of the UV-absorbing mycosporine-like amino acids (MAAs) were studied. Rapid photosynthesis vs irradiance (E) curves of freshly released spores showed that both tetraspores and carpospores were low-light adapted (E-k = 44 +/- 2 and 54 +/- 2 mu mol photons m(-2) s(-1), respectively). The light-harvesting and photosynthetic conversion efficiencies were similar (alpha = 0.13), whereas photosynthetic capacity in terms of optimum quantum yield (F-v/F-m) and relative electron transport rate (rETR(max)) were significantly higher in carpospores. Photoinhibition and recovery of photosynthesis were not significantly different between spore ploidy but were significantly affected by radiation and exposure time treatments. Accumulation of DNA damage was UV-B dose dependent and significantly higher in tetraspores than in carpospores. After 2 days postcultivation, DNA lesions were completely repaired in spores exposed to UV-B dose less than 1.2 X 10(4) J m(-2). The dynamic recovery of photosynthetic capacity as well as effective DNA repair mechanism contributed to the relatively low spore mortality (4-14%). A substantial amount of UV-screening MAAs shinorine and palythine were observed for the first time in spores of Gigartinales. This study on stress and physiological characterization of seaweed propagules is important to understand recruitment dynamics and life history phase dominance in the field.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Wulff, Angela, 1963, et al.
(författare)
-
UV radiation - a threat to Antarctic benthic marine diatoms?
- 2008
-
Ingår i: Antarctic Science. - 0954-1020. ; 20:1, s. 13-20
-
Tidskriftsartikel (refereegranskat)abstract
- This investigation was motivated by the lack of ultraviolet radiation (UVR, 280-400 nm) studies on Antarctic benthic marine microalgae. The objective was to estimate the impact of UV-B (280-315 nm) and UV-A (315-400 nm), on photosynthetic efficiency, species composition, cell density and specific growth rate in a semi-natural soft-bottom diatom community. In both experiments, cell density increased over time. The most frequently observed species were Navicula cancellata, Cylindrotheca closterium, Nitzschia spp., and Petroneis plagiostoma. For both experiments, a shift in species composition and a decreased photosystem II (PSII) maximum efficiency (F-v/F-m) over time was observed, irrespective of treatment. UVR significantly reduced F-v/F-m on days 3 and 10 (Expt 1), disappearing on the last sampling date. A similar trend was found in Expt 2. A significant UV effect on cell density was observed in Expt 1 (day 10) but not in Expt 2. No treatment effects on species composition or specific growth rate were found. Thus, the UV effects were transient (photosynthetic efficiency and cell density) and the growth of the benthic diatoms was generally unaffected. Overall, according to our results, UVR does not seem to be a threat to benthic marine Antarctic diatoms.
|
|
| 10. |
- Zacher, K., et al.
(författare)
-
Grazing and UV radiation effects on an Antarctic intertidal microalgal assemblage: a long-term field study
- 2007
-
Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 30:9, s. 1203-1212
-
Tidskriftsartikel (refereegranskat)abstract
- A 15 week field experiment (austral summer Nov-Mar) was carried out in an intertidal hard bottom platform in Antarctica (King George Island). To test whether grazing and ultraviolet radiation (UVR) influenced the succession of a benthic microalgal assemblage, a two-factorial design was used (1) ambient radiation, > 280 nm; (2) ambient minus UV-B, > 320 nm; (3) ambient minus UVR, > 400 nm versus grazer-no grazer). On four sampling occasions microalgae were identified, counted and carbon contents were calculated. The assemblage was dominated by the diatom genera Navicula and Cocconeis. Biomass was generally low in all treatments but was significantly reduced by grazing throughout the experiment. No significant UV effects were found. Grazer absence particularly favoured diatoms of the genus Cocconeis. We conclude that the Antarctic microalgal assemblage was unaffected by present day UVR whereas grazers acted as important drivers on the intertidal microalgal community structure.
|
|
