UV-B Flux Research Articles

Volcanogenic mercury and plant mutagenesis during the end-Permian mass extinction: Palaeoecological perturbation in northern Pangaea

The end-Permian extinction (EPE) (∼251.9 Ma) is considered the most severe biotic crisis in Earth’s history. Rapid climatic change and oceanic acidification triggered by Siberian Traps volcanism culminated in a widely documented mass extinction in the marine realm, but the event’s impact on terrestrial ecosystems, particularly plant communities, is less well understood. While the existence of a floral mass extinction at the Permian-Triassic Boundary (PTB) is still debated, there is mounting evidence for pervasive mutagenesis among various plant lineages, as expressed by the high incidence of aberrant spores and pollen grains. Previous studies have proposed a causal relationship between increased UV-B flux and plant mutagenesis across the PTB, yet the role of volcanically derived heavy metals as a contributing factor has received considerably less attention. Here we present the results of a high-resolution palynological, sedimentological, and geochemical analysis of a continuous and previously unstudied PTB section from the Norwegian Arctic. The study reveals an abrupt increase in the levels of heavy metals across the EPE negative carbon isotope excursion (CIE). Palynological analysis indicates disruption, and a phased transition of plant communities at the PTB, without a significant turnover in species or decrease in diversity. However, the abrupt appearance and elevated abundance of aberrant palynomorphs coincides with increased concentrations of As, Co, Hg, and Ni, which is interpreted as compelling evidence for heavy metal-induced stress and genetic disturbance in plant communities during the EPE. We hypothesise that biomagnification of these elements may have been a significant driver for the end-Permian biotic crisis. Our findings are correlated via biostratigraphy and chemostratigraphy with other circum-Arctic PTB sections described in the literature, demonstrating the isochroneity and facies independence of these widespread palaeoecological changes.

Response to Comment on "Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction".

Seddon and Zimmermann have raised questions about the evidence for increased UV-B flux across the end-Permian mass extinction (EPME) that was presented in our recent study, specifically regarding the measurement of UV-B-absorbing compound (UAC) levels in fossil pollen. We respond to these points, arguing that the comparison of FTIR spectra of >250 million-year-old Permian fossil pollen with ~700-year-old subfossil pollen is not valid and that negligible nonrandom interference derived from water vapor fluctuations during data generation cannot coincidentally produce a substantial UAC peak during the EPME. Furthermore, we refute the suggestion that the measured aromatic peak at 1600 cm-1 could have been influenced by diagenetic products from other organic constituents of pollen. The most productive route forward will be to generate sporomorph geochemical data from additional Permian-Triassic boundary sections to test the results put forward in our study.

Sunlight Degradation of the Aminophosphonate Diethylenetriamine Penta-(Methylenephosphonic Acid)

Aminophosphonate diethylenetriamine penta(methylenephosphonic acid) (DTPMP) is a scale inhibitor commonly used in several industries. DTPMP is suspected to cause anthropogenic pollution through discharge into the aquatic environment. DTPMP is assumed to be degraded by sunlight radiation. We recently predicted a preliminary degradation pathway of DTPMP applying UV treatment. Currently, we have not yet evidenced that DTPMP shows the same degradation pattern with natural sunlight. One major reason leads to the fact that the light spectrum emitted by UV lamps does not completely represent the natural sunlight spectrum, and the emitted UVB and UVA irradiation flux is much higher than for solar light. For that reason, the degradation pattern and kinetics might be different between artificial UV treatment and natural sunlight treatment. Here, we investigated whether DTPMP is degradable under natural sunlight radiation, and whether the degradation mechanisms determined through UV treatment are transferable to sunlight. We investigated five different treatment conditions, i.e., DTPMP degradation in direct or diffuse sunlight, in diffuse sunlight with addition of Ca2+ or Mg2+, and in diffuse sunlight with local TW. Our experiment was carried out from March 2021 to October 2021. We performed LC/MS analyses and measured the release of o-PO43−. DTPMP was degraded with all five treatment conditions. The fastest DTPMP degradation occurred in direct and diffuse sunlight without addition of bivalent cations. The addition of Ca2+ and Mg2+ resulted in inhibited degradation. Similar effects occurred for sunlight treatment with local TW. We evidenced different degradation mechanisms for DTPMP depending on the presence of alkaline earth metals as we previously proposed for UV-treated DTPMP. However, both degradation mechanisms of DTPMP belong to the same degradation pathway determined with UV treatment. Therefore, we conclude that DTPMP undergoes a similar degradation pathway in sunlight as compared to UV light.

SUNLIGHT AND SARS-COV-2: CAN SUNLIGHT AND UV EXPOSURE MITIGATE THE PROPAGATION OF COVID-19?

Background: This review aims to assess the contributing role of sunlight on mitigating the propaga­tion of COVID-19, and to assess how sunlight as well as artificial UV light may be a natural, more cost effective and eco-friendly method of disinfection which can be implemented in order to help to combat this rampant pandemic. Methods: An extensive literature survey of English literature was conducted using Pubmed, Pubmed Central, Medline, Google Scholar and WHO Nepal Situation Updates on COVID-19. A combination of keywords was entered: “Sunlight” OR “Disinfection”; OR “Ultraviolet Rays”; OR “SARS-CoV-2”; OR “Coronavirus Disease 2019”; OR “COVID 19”; AND ‘Nepal’. Results: Sunlight is composed of UVA (95%) and UVB (5%) radiation, UVB is most effective to inac­tivate SARS-CoV-2 and does so by damaging the RNA genome of the virus, and increasing levels of reactive oxygen species in the air. SARS-CoV-2 is nullified by a UVB flux of 28 J/m2, and needs to be exposed for a sufficient duration depending on the time of day, season, geographic location or the specific locality, in order to be inactivated. Conclusion: Developing countries could benefit from taking advantage of using sunlight as a cost-free and environmentally friendly method of disinfection. It is imperative that all countries capital­ize on this method of disinfection, it is cost-free, easy and therefore can be implemented on a large scale with relative ease.

Narrow-Band 311 nm Ultraviolet-B Radiation Evokes Different Antioxidant Responses from Broad-Band Ultraviolet.

Supplemental narrow-band 311 nm UV-B radiation was applied in order to study the effect of this specific wavelength on tobacco as a model plant. UV-B at photon fluxes varying between 2.9 and 9.9 μmol m−2 s−1 was applied to supplement 150 μmol m−2 s−1 photosynthetically active radiation (PAR) for four hours in the middle of the light period for four days. Narrow-band UV-B increased leaf flavonoid and phenolic acid contents. In leaves exposed to 311 nm radiation, superoxide dismutase activity increased, but phenolic peroxidase activity decreased, and the changes were proportional to the UV flux. Ascorbate peroxidase activities were not significantly affected. Narrow-band UV-B caused a dose-dependent linear decrease in the quantum efficiency of photosystem II, up to approximately 10% loss. A parallel decrease in non-regulated non-photochemical quenching indicates potential electron transfer to oxygen in UV-treated leaves. In addition to a flux-dependent increase in the imbalance between enzymatic H2O2 production and neutralization, this resulted in an approximately 50% increase in leaf H2O2 content under 2.9–6 μmol m−2 s−1 UV-B. Leaf H2O2 decreased to control levels under higher UV-B fluxes due to the onset of increased non-enzymatic H2O2- and superoxide-neutralizing capacities, which were not observed under lower fluxes. These antioxidant responses to 311 nm UV-B were different from our previous findings in plants exposed to broad-band UV-B. The results suggest that signaling pathways activated by 311 nm radiation are distinct from those stimulated by other wavelengths and support the heterogeneous regulation of plant UV responses.

Effects of Temperature on The UV-B Sensitivity of Toxic Cyanobacteria Microcystis aeruginosa CS558 and Anabaena circinalis CS537.

Rising global temperatures have been suggested to favor cyanobacteria over eukaryotic algae, but UV-B fluxes are also predicted to remain high and may interact with temperature to affect algal growth. To understand the interactive effects of temperature and UV-B radiation, cultures of Microcystis aeruginosa and Anabaena circinalis were grown at either 25 or 30°C and then exposed to an acute irradiance of UV-B (1.4Wm-2 ). Both species showed differences in growth rates at both temperature regimes. The growth rates of M.aeruginosa (0.41±0.02day-1 ) and A.circinalis (0.38±0.01day-1 ) were higher at 25 and 30°C, respectively. Rates of damage (k) and repair (r) were calculated from the kinetics of change in effective quantum yield, Fv '/Fm '. Analysis of the estimates of r and k shows that M.aeruginosa exhibited relatively high values for both parameters, compared to A.circinalis, at both growth temperatures. In both species, repair rates were higher at 30°C than at 25°C but in A.circinalis damage was also greater at the higher temperature. In contrast, M.aeruginosa showed a lower damage rate at the higher temperature. For both species, the ratio of r:k was higher at the higher temperature. However, the percent inhibition of effective quantum yield by UV-B was greater in A.circinalis than in M.aeruginosa as the r:k was lower A.circinalis. Therefore, it could be concluded that temperature may influence growth and bloom formation of cyanobacteria and that different species may respond differently to UV-B and temperature interactions.

Effect of environmental variables on phytonutrients of Origanum vulgare L. in the sub-humid region of the northwestern Himalayas.

Ecological and soil physiochemical parameters impact the crop quality and development. In spite of the huge commercial prospective, the phytonutrient and chemometric profiles of Himalayan oregano (Origanum vulgare L.) have not been evaluated, and their relationships with ecological parameters are still lacking. The objective of this research study was to evaluate the disparity in the phytonutrient profiles of different ecotypes of O. vulgare in wild and cultivated populations and determine whether such variation was related to the diverse climatic and edaphic conditions prevailing in the northwestern Himalayas. Micrometeorological, atomic absorption spectroscopy for micro-elemental analysis was determined for soil. HPLC was used to determine the disparity in phytonutrient (quercetin, betacarotene, ascorbic acid, and catechin) and phytochemical (arbutin) levels. Cultivated populations had lower phytonutrient levels than wild populations. The habitat exhibiting pH values ranging from 6 to 7 elevated organic carbon (2.42%), nitrogen (97.41kgha-1), and manganese (10-12μgg-1) and zinc contents (0.39-0.50%) show luxirant growth of Origanum vulgarel. The phytonutrient (quercetin, betacarotene, ascorbic acid, arbutin, and catechin) levels had a direct relationship with UV-B flux (r2 = 0.82) and potassium (r2 = 0.97). Wild accessions predominantly contained catechin and ascorbic acid, with maximum values of 163.8 and 46.88μg g-1, respectively, while the cultivated accessions had the highest level of arbutin (53.42μg g-1). Maximum variation was observed in quercetin (114.61%) followed by β-carotene (87.53%). Cultivated accessions had less quercetin (0.04-1.25μg g-1) than wild accessions (1.25-2.87μg g-1). Wild accessions had higher phytonutrient values for catechin, β-carotene, and ascorbic acid while cultivated accessions had maximum values for arbutin. The correlation of environmental variables with phytonutrient levels paves the way for metabolomic-guided enhancement of agricultural practices for better herb quality.

UV-B-absorbing compounds in modern Cedrus atlantica pollen: The potential for a summer UV-B proxy for Northwest Africa

Sporopollenin is a complex biopolymer which is the main component of the pollen grain exine and is partly composed of the aromatic compounds para-coumaric acid ( pCA) and ferulic acid (FA). These compounds absorb ultraviolet-B radiation (UV-B, 280–315 nm), and their abundance in pollen and spores has been shown to increase in response to increased UV-B flux. Here, we show that the relative abundance of UV-B-absorbing compounds (UACs) measured using Fourier Transform Infrared Spectrometry (FTIR) in modern pollen of autumn-pollinating Cedrus atlantica trees increases in response to summer UV-B flux. This relationship was observed in native Moroccan samples ( r2 = 0.84, p < 0.0001), but not across a larger environmental gradient including non-Moroccan samples ( r2 = 0.00, p = 0.99). For non-Moroccan samples of known provenance, the abundance of UACs is similar to the abundance of UACs found in samples from their place of origin. The FTIR spectra of these samples also closely resemble the FTIR spectra of samples from their place of origin. This unexpected finding suggests there could be a heritable component to UAC production possibly associated with epigenetic memory, an important adaptive mechanism in conifers. Our results indicate that the relative abundance of UACs in Cedrus atlantica pollen could be used as a proxy to reconstruct historic summer UV-B flux in Northwest Africa during at least the Holocene and Late Glacial period while also highlighting how UV-B proxies should be established using pollen samples from specimens growing in their native range or environment.

Quantifying the impact of sulfate geoengineering on mortality from air quality and UV-B exposure

Sulfate geoengineering is a proposed method to partially counteract the global radiative forcing from accumulated greenhouse gases, potentially mitigating some impacts of climate change. While likely to be effective in slowing increases in average temperatures and extreme precipitation, there are known side-effects and potential unintended consequences which have not been quantified. One such consequence is the direct human health impact. Given the significant uncertainties, we take a sensitivity approach to explore the mechanisms and range of potential impacts. Using a chemistry-transport model, we quantify the steady-state response of three public health risks to 1 °C global mean surface cooling. We separate impacts into those which are “radiative forcing-driven”, associated with climate change “reversal” through modification of global radiative forcing, and those “direct impacts” associated uniquely with using sulfate geoengineering to achieve this. We find that the direct (non-radiative forcing driven) impact is a decrease in global mortality of ∼13,000 annually. Here the benefits of reduced ozone exposure exceed increases in mortality due to UV and particulate matter, as each unit of injected sulfur incurs 1/25th the particulate matter exposure of a unit of sulfur emitted from surface sources. This reduction is exceeded by radiative forcing-driven health impacts resulting from using sulfate geoengineering to offset 1 °C of surface temperature rise. Increased particulate matter formation at these lower temperatures results in ∼39,000 mortalities which would have been avoided at higher temperatures. As such we estimate that sulfate geoengineering in 2040 would cause ∼26,000 (95% interval: −30,000 to +79,000) early deaths annually relative to the same year without geoengineering, largely due to the loss of health benefits associated with CO2-induced warming. These results account only for impacts due to changes in air quality and UV-B flux. They do not account for non-mortality impacts or changes in atmospheric dynamics, and must be considered in the wider context of other climate change impacts such as heatwave frequency and sea level rise.

Spatio-temporal assessment and seasonal variation of tropospheric ozone in Pakistan during the last decade

This study uses the tropospheric ozone data derived from combined observations of Ozone Monitoring Instrument/Microwave Limb Sounder instruments by using the tropospheric ozone residual method. The main objective was to study the spatial distribution and temporal evolution in the troposphere ozone columns over Pakistan during the time period of 2004 to 2014. Results showed an overall increase of 3.2 ± 1.1DU in tropospheric ozone columns over Pakistan. Spatial distribution showed enhanced ozone columns in the Punjab and southern Sindh consistent to high population, urbanization, and extensive anthropogenic activities, and exhibited statistically significant temporal increase. Seasonal variations in tropospheric ozone columns are driven by various factors such as seasonality in UV-B fluxes, seasonality in ozone precursor gases such as NOx and volatile organic compounds (caused by temperature dependent biogenic emission) and agricultural fire activities in Pakistan. A strong correlation of 96% (r = 0.96) was found between fire events and tropospheric ozone columns in Pakistan.

Accumulation and partitioning of anthocyanins in two red grape cultivars under natural and reduced UV solar radiation

Background and Aims Plant responses to solar radiation are difficult to quantify due to interannual weather variation and to interference by other environmental factors. This study assesses the extent of the effect of UV sunlight on the accumulation and partitioning of anthocyanins in the berry skin of two red grape cultivars. Methods and Results Ultraviolet screening treatments, visible + UV-A and visible, applied to Bovale Grande (syn. Carignan) and Cannonau (syn. Grenache) field-grown vines, in Sardinia, Italy, promoted a significant difference in the concentration of skin anthocyanins compared with that of plants exposed to natural sunlight. Thermal units for anthocyanin accumulation, estimated with an adjusted normal heat hours model, showed a highly significant difference between cultivars. The elevated duration of high temperature (HT>35°C) in the first season reduced the concentration of skin anthocyanins, with Cannonau showing greater sensitivity. Together with the light regimes, HT>35°C induced an alteration in the composition of the anthocyanins; both natural UV-B and low flux of UV-A promoted higher acylation. Conclusions Besides light intensity, spectral composition also influenced accumulation and partitioning of anthocyanins in berry skin. The extent of alteration differs among cultivars as the combined effect of natural UV and HT>35°C drives shifts in anthocyanins biosynthesis differently. Significance of the Study Extending knowledge of the role played by sunlight and temperature on accumulation of berry anthocyanins may help to define management practices that foster stability of berry must colour and favour an optimal phenolic profile.

Vitamin D production after UVB exposure – A comparison of exposed skin regions

BackgroundCholecalciferol is an essential steroid produced in the skin by solar ultraviolet B radiation (UVB 290–315nm). Skin production of cholecalciferol depends on factors affecting UVB flux, age and exposed skin area. PurposeSerum cholecalciferol and 25-hydroxyvitamin D3 [25(OH)D3] concentrations were measured after UVB irradiation of 3 different skin areas to compare the skin capacity to produce vitamin D in different anatomic sites in the same individuals. MethodTen voluntary Caucasians (skin photo type II & III, aged 48±12years (±SD)) were exposed to broadband UVB (280–320nm) between February and April. Hands and face, upper body and whole body were exposed to a suberythemic dose of UVB (median 101mJ/cm2 (min 66, max 143)) (for 3 subsequent days 24h apart with a wash out period of about 3weeks (median 18days (min 11, max 25)) between the exposures of respective area. Serum concentrations of cholecalciferol and 25(OH)D3, were measured immediately before the first and 24h after the last dose of radiation. ResultsThere was a significantly higher increase in serum cholecalciferol after UVB exposure of the two larger skin areas compared to face and hands, but no difference in increase was found between upper body and whole body exposures. ConclusionExposure of a larger skin area was superior to small areas and gave greater increase in both serum cholecalciferol and serum 25(OH)D3 concentrations. However, exposure of face and hands, i.e. only 5% of the body surface area, was capable of increasing serum concentrations of 25(OH)D3.

Kya jalavaayu parivartan saur badalaav se prabhaavit hota hai?

At present, climate change is a matter of great concern to mankind. This change, which is due to the manmade activities, is changing global temperature and the concentration of CO2 and O3 in the atmosphere. But there are some changes in the sun also. Solar changes could be assessed by solar flux at 10.7cm wavelength. Climate change could be assessed by long time temperature records. In this study we have examined whether solar change has any effect on climate change? We have analyzed two sets of data, 10.7cm solar flux (TSI) and global temperature record, along with total ozone, UV-B flux at ground and satellite data of total solar irradiance. Global temperature anomaly curve (GTAC) shows a slow increase of temperature up to about 1975 and a rapid rise after this year. Solar flux at 10.7cm wavelength shows a decreasing trend up to about 1970 and an increasing trend after this year. It also has 11 year cycle. GTAC, total ozone, UV-flux at ground and TSI also show 11 year cycle and some trend, but none of them matches the long-term trend found in solar flux at 10.7cm wavelength.

CO2 concentrating mechanisms and environmental change

The diversity of CCMs among aquatic oxygenic photolithotrophs causes difficulties in generalising about their responses to environmental change. A frequent response of organisms with CCMs to increasing CO2 is increased organic carbon content, even if (as is often the case) the growth rate is not increased. In the few studies performed, the internal carbon dioxide concentration relative to the growth carbon dioxide concentration is decreased for organisms grown at elevated CO2, but not sufficiently so to alter the degree of Rubisco saturation with CO2. The more commonly measured affinity for external CO2 generally also decreases with increased CO2 concentration for growth. The present global distribution of cyanobacteria and algae with CCMs over a wide temperature range contrasts with terrestrial C4 plants which mainly grow in warmer habitats. This suggests that algae and cyanobacteria will benefit less from increasing global temperatures in terms of geographical range than will terrestrial C4 plants. The general correlate of increased temperature and a shallowing (shoaling) of the thermocline means that phytoplankton will experience a higher mean PAR and UV-B flux, and a decreased availability of combined nitrogen, phosphorus and iron. The general conclusion is that this combination of environmental changes will in part offset the decreased CCM activity in response to increased CO2. The few data available on responses to environmental change of the minority of aquatic oxygenic photolithotrophs lacking CCMs, suggest some similarities of responses of these organisms and those with CCMs. Organic carbon burial (“blue carbon”) by undisturbed seagrass beds will probably increase under environmental change.

Analysis of UV-absorbing photoprotectant mycosporine-like amino acid (MAA) in the cyanobacterium Arthrospira sp. CU2556.

Mycosporine-like amino acids (MAAs) are ecologically important biomolecules with great photoprotective potential. The present study aimed to investigate the biosynthesis of MAAs in the cyanobacterium Arthrospira sp. CU2556. High-performance liquid chromatography (HPLC) with photodiode-array detection studies revealed the presence of a UV-absorbing compound with an absorption maximum at 310 nm. Based on its UV absorption spectrum and ion trap liquid chromatography/mass spectrometry (LC/MS) analysis, the compound was identified as a primary MAA mycosporine-glycine (m/z: 246). To the best of our knowledge this is the first report on the occurrence of MAA mycosporine-glycine (M-Gly) in Arthrospira strains studied so far. In contrast to photosynthetic activity under UV-A radiation, the induction of the biosynthesis of M-Gly was significantly more prominent under UV-B radiation. The content of M-Gly was found to increase with the increase in exposure time under UV-B radiation. The MAA M-Gly was highly stable under UV radiation, heat, strongly acidic and alkaline conditions. It also exhibited good antioxidant activity and photoprotective ability by detoxifying the in vivo reactive oxygen species (ROS) generated by UV radiation. Our results indicate that the studied cyanobacterium may protect itself by synthesizing the UV-absorbing/screening compounds as important defense mechanisms, in their natural brightly-lit habitat with high solar UV-B fluxes.

Biological radiation dose from secondary particles in a Milky Way gamma-ray burst

AbstractGamma-ray bursts (GRBs) are a class of highly energetic explosions emitting radiation in a very short timescale of a few seconds and with a very narrow opening angle. Although, all GRBs observed so far are extragalactic in origin, there is a high probability of a GRB of galactic origin beaming towards the Earth in the past ∼0.5 Gyr. We define the level of catastrophic damage to the biosphere as approximation 100 kJ m−2, based on Thomas et al. (2005a, b). Using results in Melott & Thomas (2011), we estimate the probability of the Earth receiving this fluence from a GRB of any type, as 87% during the last 500 Myr. Such an intense burst of gamma rays would ionize the atmosphere and deplete the ozone (O3) layer. With depleted O3, there will be an increased flux of Solar UVB on the Earth's surface with potentially harmful biological effects. In addition to the atmospheric damage, secondary particles produced by gamma ray-induced showers will reach the surface. Among all secondary particles, muons dominate the ground-level secondary particle flux (99% of the total number of particles) and are potentially of biological significance. Using the Monte Carlo simulation code CORSIKA, we modelled the air showers produced by gamma-ray primaries up to 100 GeV. We found that the number of muons produced by the electromagnetic component of hypothetical galactic GRBs significantly increases the total muon flux. However, since the muon production efficiency is extremely low for photon energies below 100 GeV, and because GRBs radiate strongly for only a very short time, we find that the biological radiation dose from secondary muons is negligible. The main mechanism of biological damage from GRBs is through Solar UVB irradiation from the loss of O3 in the upper atmosphere.

Surrogates of Long-Term Vitamin D Exposure and Ovarian Cancer Risk in Two Prospective Cohort Studies

Experimental evidence and ecologic studies suggest a protective role of vitamin D in ovarian carcinogenesis. However, epidemiologic studies using individual level data have been inconsistent. We evaluated ultraviolet (UV)-B radiation, vitamin D intake, and predicted plasma 25-hydroxyvitamin D [25(OH)D] levels as long-term surrogates of vitamin D exposure within the Nurses’ Health Study (NHS) and NHSII. We estimated incidence rate ratios (RRs) and 95% confidence intervals (CIs) for risk of overall ovarian cancer and by histologic subtype using Cox proportional hazards models. Between 1976 and 2010 in NHS and 1989 and 2011 in NHSII, we identified a total of 1,225 incident epithelial ovarian cancer cases (NHS: 970, NHSII: 255) over 4,628,648 person-years of follow-up. Cumulative average UV-B exposure was not associated with ovarian cancer risk in NHS (Ptrend = 0.08), but was associated with reduced risk in NHSII (highest vs. lowest category RR = 0.67; 95% CI: 0.50, 0.89; Ptrend < 0.01). When stratified by histologic subtype, UV-B flux was positively associated with risk of serous tumors in NHS (Ptrend < 0.01), but inversely associated in NHSII (Ptrend = 0.01). Adjusted for confounders, ovarian cancer risk was not associated with vitamin D intake from food or supplements or with predicted 25(OH)D levels. Our study does not strongly support a protective role for vitamin D in ovarian cancer risk.

UV radiation-induced accumulation of photoprotective compounds in the green alga Tetraspora sp. CU2551

The effect of UV radiation on the accumulation of novel mycosporine-like amino acids (MAAs) along with their photoprotective function was investigated in the green alga Tetraspora sp. CU2551. No UV-absorbing compound was detected in this organism growing under normal light condition while two MAAs with absorption maxima at 324nm and 322nm were found to be accumulated after UV irradiation. The effects of UV exposure time with different cut-off filter foils namely 295 (PAR+UV-A+UV-B), 320 (PAR+UV-A) and 395nm (PAR only) were studied on induction of the synthesis of these MAAs. Concentration of MAAs was found to increase with increase in exposure time under UV radiation. Furthermore, the antioxidant and photoprotective action of these MAAs was also investigated. The role of MAAs in diminishing the UV-induced production of ROS invivo was also demonstrated using the oxidant-sensing probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and results obtained supported the results of DPPH free radical scavenging assay. The MAAs also exhibited efficient photoprotective ability on Escherichia coli cells against UV-B stress. Thus, the MAAs in Tetraspora sp. CU2551 may act as efficient antioxidants as well as UV-sunscreen. This is the first report for the UV-induced synthesis and co-accumulation of these MAAs and their photoprotective actions in Tetraspora sp. which is a member of the class Chlorophyceae. Moreover, UV-induced accumulation as well as photoprotective function of these compounds may facilitate this chlorophyte to perform important ecological functions in harsh environmental conditions with high UV-B fluxes in their brightly lit habitats.

UV-B as a Photoacclimatory Enhancer of the Hermatypic Coral &amp;lt;i&amp;gt;Stylophora pistillata&amp;lt;/i&amp;gt;

Photoacclimation processes are crucial for the survival of all photosynthetic organisms in the photic zone. Changes in photosynthetic active radiation (PAR) are however simultaneous to changes in UV-B radiation. The influence of UV-B levels on bio-optical and physiological parameters of deep (30 m) corals from the species Stylophora pistillata and their symbiotic algae, zooxanthellae, was examined during their gradual, stepwise acclimation to a shallow depth (3 m). Drastic exposure of deeper corals to higher UV-B levels in shallower depths is usually fatal. Hence, the acclimation process lasted 118 days and included 10 intermediate stations with an addition of similar amount of PAR at each depth transfer. Concomitantly, in an on-shore experiment, fragments from the same colonies were acclimated by changing shading nets corresponding in PAR levels to each in situ station. Since UV-B is attenuated more efficiently than PAR in seawater, the PAR: UV-B ratio changes in the depth experiment while remaining constant under the neutral density nets. This provided the opportunity to evaluate the importance of UV-B to photoacclimation. In both experiments all fragments survived, in spite of a four-fold difference in levels of PAR and a 140-fold difference in UV-B flux between the initial and final conditions. Both experimental designs resulted in reduction of zooxanthellae density, photosynthesis rates, and quantum yields of PSII, while cellular chlorophyll content remained unaffected. Zooxanthellae density and maximal photosynthetic rate was found decreased in correlation with UV-B radiation, whether it was elevated logarithmically with reducing depths or linearly with reducing shades. Conversely, quantum yields of PSII were adjusted according to the enhancement of PAR rather than UV-B. We conclude that UV-B enhances the magnitude of photoacclimation to higher PAR. This novel aspect of photoacclimation can provide the basis for our understanding of the underlying mechanisms that result in UV-related bleaching.

Development of a method to quantify UV-B flux during the Quaternary using UV-B absorbing compounds contained in fossil Pinus spp. sporopollenin

Development of a method to quantify UV-B flux during the Quaternary using UV-B absorbing compounds contained in fossil Pinus spp. sporopollenin