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Haematopoietic stem and progenitor cells (HSPCs) require a specific microenvironment, the haematopoietic niche, which regulates HSPC behaviour.sup.1,2. The location of this niche varies across species, but the evolutionary pressures that drive HSPCs to different microenvironments remain unknown. The niche is located in the bone marrow in adult mammals, whereas it is found in other locations in non-mammalian vertebrates, for example, in the kidney marrow in teleost fish. Here we show that a melanocyte umbrella above the kidney marrow protects HSPCs against ultraviolet light in zebrafish. Because mutants that lack melanocytes have normal steady-state haematopoiesis under standard laboratory conditions, we hypothesized that melanocytes above the stem cell niche protect HSPCs against ultraviolet-light-induced DNA damage. Indeed, after ultraviolet-light irradiation, unpigmented larvae show higher levels of DNA damage in HSPCs, as indicated by staining of cyclobutane pyrimidine dimers and have reduced numbers of HSPCs, as shown by cmyb (also known as myb) expression. The umbrella of melanocytes associated with the haematopoietic niche is highly evolutionarily conserved in aquatic animals, including the sea lamprey, a basal vertebrate. During the transition from an aquatic to a terrestrial environment, HSPCs relocated into the bone marrow, which is protected from ultraviolet light by the cortical bone around the marrow. Our studies reveal that melanocytes above the haematopoietic niche protect HSPCs from ultraviolet-light-induced DNA damage in aquatic vertebrates and suggest that during the transition to terrestrial life, ultraviolet light was an evolutionary pressure affecting the location of the haematopoietic niche.Melanocytes above the haematopoietic niche protect haematopoietic stem cells from ultraviolet-light-induced DNA damage in aquatic vertebrates throughout evolution; this niche moved to the bone marrow during the transition to terrestrial life., Author(s): Friedrich G. Kapp [sup.1] [sup.2] [sup.3] , Julie R. Perlin [sup.1] [sup.2] , Elliott J. Hagedorn [sup.1] [sup.2] , John M. Gansner [sup.4] , Daniel E. Schwarz [sup.5] , [...]

Abstract This study investigates the extra UV fluence needed to meet the International Maritime Organisation's ballast water discharge standards for the 10–50 μm size-class using the approved vital stain (VS) method compared to the Most Probable Number (MPN) method for organism viability assessment. Low- and medium pressure UV collimated beam treatments were applied to natural algae collected in temperate and tropical water environments and analysed using both methods. About 10 times higher UV fluence was required to meet discharge standards when using VS compared to MPN. Implementing a dark-hold period after UV treatments decreased algal viability. Length of dark-hold period to meet discharge standards decreased with increasing UV fluence. No significant differences between temperate and tropical samples were observed. The results showed that UV treated algae assessed using the VS method could meet discharge standards by increasing fluence and/or introducing a dark-hold period. Highlights • Compliance achieved with vital stain by increasing UV fluence 10–15 times • Compliance achieved with vital stain by introducing dark hold periods • Algae <10 μm need more attention as they potentially hold high invasive potential. [ABSTRACT FROM AUTHOR]

Abstract: Increases in ultraviolet radiation (UVR) levels due to the ongoing stratification of water bodies and higher nutrient concentrations either through riverine or aeolian‐dust‐inputs are expected in the near future in coastal surface waters. Here, we combined remote‐sensing data of particulate organic carbon (POC; 1997–2016 period), observational data of solar radiation (1999–2015 period), and a mid‐term experimental approach with coastal plankton communities from South Atlantic Ocean (SAO) to test how the interaction between increased nutrients by riverine and aeolian‐dust inputs and high UVR may alter the community dynamics and the CO2 sink capacity of these ecosystems in the future. Our results show a decline ∼ 27% in the sink capacity of the coastal ecosystems regardless of the nutrient source considered and under high UVR levels. This decreased CO2 uptake was coupled with a high dynamic photoinhibition and dark recovery of photosystem II and shifts in the community structure toward the dominance by nano‐flagellates. Moreover, remote‐sensing data also evidences an incipient tipping point with decreasing POC values in this area over the annual planktonic succession. Therefore, we propose that to continue this climate and human‐mediated pressure, these metabolic responses could be strengthened and extended to other productive coastal areas. [ABSTRACT FROM AUTHOR]

Organic UV stabilizers and UV filters are applied to industrial materials and cosmetics worldwide. In plastics they prevent photo-induced degradation, while in cosmetics they protect human skin against harmful effects of UV radiation. This study reports on the occurrence and distribution of organic UV stabilizers and UV filters in the surface sediment of the Chinese Bohai and Yellow Seas for the first time. In total, 16 out of 21 analyzed substances were positively detected. Concentrations ranged from sub-ng/g dw to low ng/g dw. The highest concentration of 25 ng/g dw was found for octocrylene (OC) in the Laizhou Bay. In the study area, characteristic composition profiles could be identified. In Korea Bay, the dominating substances were OC and ethylhexyl salicylate (EHS). All other analytes were below their method quantification limit (MQL). Around the Shandong Peninsula, highest concentrations of benzotriazole derivatives were observed in this study with octrizole (UV-329) as the predominant compound, reaching concentrations of 6.09 ng/g dw. The distribution pattern of UV-329 and bumetrizole (UV-326) were related (Pearson correlation coefficient r > 0.98, p « 0.01 around the Shandong Peninsula), indicating an identical input pathway and similar environmental behavior. [ABSTRACT FROM AUTHOR]

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 ± 1.1 DU 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. [ABSTRACT FROM AUTHOR]

Objectives Ultraviolet radiation (UVR), with UVB and UVA as the relevant components, is a risk factor for melanoma. Complete ascertainment and registration of melanoma in Iran was conducted in five provinces (Ardabil, Golestan, Mazandaran, Gilan and Kerman) during 1996–2000. The aim of our study was to compare population-based incidence data from these provinces with rates in the United States (US) while standardizing ambient UVR. Methods Population-based rates representing all incident cases of melanoma (1996–2000) across the five Iranian provinces were compared to rates of melanoma among white non-Hispanics in the US. Overall age-standardized rates (ASR) for Iran and the US (per 100,000 person-years adjusted to 2000 world population) and standardized rate ratios (SRR) were calculated. We measured erythemally-weighted average solar UVR exposures (with contributions from both UVB and UVA range) of the five Iranian provinces using data from NASA's Total Ozone Mapping Spectrometer and selected five US states (Kentucky, Utah, Texas, Oklahoma, and Hawaii) with matching UVR exposure to each province. Incidence rates of melanoma during 1996–2000 in each Iranian province were compared to rates among white non-Hispanics in its UVR-matched US state. Results The overall male and female ASRs of melanoma were 0.60 (95%CI: 0.56–0.64) and 0.46 (95%CI: 0.42–0.49), respectively, for Iran and 22.78 (95%CI: 22.42–23.14) and 16.61 (95%CI: 16.30–16.92) for the US. SRRs of melanoma comparing US to Iran were 37.97 (95%CI: 35.78–40.29) for males and 36.11 (95%CI: 33.69–38.70) for females, indicating significantly higher incidence in the US. ASRs and age-specific rates of melanoma for both genders were significantly lower in each Iranian province compared to its UVR-matched US state. Conclusion The markedly lower incidence rates of melanoma in Iranian provinces with similar UVR exposures to US states underscore the need for additional comparative studies to decipher the influence of other extrinsic and intrinsic factors on the risk of this malignancy. [ABSTRACT FROM AUTHOR]

In this paper, data obtained by the Vernov satellite are discussed in comparison with the data obtained by Universitetsky-Tatiana-1, 2 satellites. The advanced instrumentation onboard the Vernov satellite improved the capabilities of the data-transmission system, providing an opportunity to acquire more detailed information on transient atmospheric events (TAEs), including a wider range of TAE photon numbers (event brightness) down to lower photon numbers, the opportunity to observe the events in ultraviolet range without the considerable inclusion of red-infrared photons (which indicates the substantial contribution of electric discharges, lightning precursors, at the altitudes of thunderstorm clouds), and the observation of TAE series at a rate of about 10-100 occurrences per second with a period from tens of seconds to several minutes. [ABSTRACT FROM AUTHOR]

Phormidium tenue, a cyanobacterium that grows in the topsoil of biological soil crusts (BSCs), has the highest recovery rate among desert crust cyanobacteria after exposure to ultraviolet B (UV-B) radiation. However, the mechanism underlying its recovery process is unclear. To address this issue, we measured chlorophyll a fluorescence, generation of reactive oxygen species (ROS), lipid peroxidation, and repair of DNA breakage in P. tenue following exposure to UV-B. We found that UV-B radiation at all doses tested reduced photosynthesis and induced cell damage in P. tenue . However, P. tenue responded to UV-B radiation by rapidly reducing photosynthetic activity, which protects the cell by leaking less ROS. Antioxidant enzymes, DNA damage repair systems, and UV absorbing pigments were then induced to mitigate the damage caused by UV-B radiation. The addition of exogenous antioxidant chemicals ascorbate and N-acetylcysteine also mitigated the harmful effects caused by UV-B radiation and enhanced the recovery process. These chemicals could aid in the resistance of P. tenue to the exposure of intense UV-B radiation in desertified areas when inoculated onto the sand surface to form artificial algal crusts. [ABSTRACT FROM AUTHOR]

Tetramethylammonium hydroxide (TMAH) is widely used in high-tech industries as a developing agent. Ultraviolet (UV) light–activated persulfate (PS, S2O82−) can be used to generate strongly oxidative sulfate radicals, and it also exhibits the potential to treat TMAH-containing wastewater. This study initially investigated the effect of S2O82−concentration and UV strength on the UV/S2O82−process for the degradation of TMAH in a batch reactor. The results suggested that 15 watts (W) of UV-activated S2O82−at concentrations of 10 or 50 mM resulted in pseudo-first-order TMAH degradation rate constants of 3.1–4.2 × 10−2min−1, which was adopted for determining the hydraulic retention time (HRT) in a continuous stirred tank reactor (CSTR). The operating conditions (15 W UV/10 mM S2O82−) with a HRT of 129 min resulted in stable residual concentrations of S2O82−and TMAH at approximately 2.6 mM and 20 mg L−1in effluent, respectively. Several TMAH degradation intermediates including trimethylamine, dimethylamine, and methylamine were also detected. The effluent was adjusted to a neutral pH and evaluated for its biological acute toxicity usingCyprinus carpioas a bioassay organism. The “bio-acute toxicity unit” (TUa) was determined to be 1.41, which indicated that the effluent was acceptable for being discharged into an aquatic ecosystem. [ABSTRACT FROM PUBLISHER]

Prunella vulgarisplants (full-bloom stage) were subjected to short-term (15 days) UV-B radiation in a growth chamber. UV-B radiation was effective at enhancing morphological and biomass characteristics and decreasing chlorophyll contents ofP. vulgaris. Treatment ofP. vulgariswith artificial UV-B radiation significantly increased peroxidase (POD), superoxide dismutase (SOD) and glutathione (GSH) activities compared to the control treatment. UV-B radiation significantly increased the levels of hydrogen peroxide (H2O2), malondialdehyde (MDA) and proline in leaves ofP. vulgariscompared to those of control plants. In addition, the contents of total flavonoids, rosmarinic acid, caffeic acid and hyperoside significantly increased under UV-B radiation. The total phenolic levels also increased under UV-B treatment. These results demonstrated that short-term UV-B radiation can enhance production of secondary metabolites inP. vulgaris, resulting in increased spica yield compared to that of control plants. [ABSTRACT FROM AUTHOR]

Benzotriazole ultraviolet stabilizers (BUVSs) are prominent chemicals widely used in industrial and consumer products to protect against ultraviolet radiation. They are becoming contaminants of emerging concern since their residues are frequently detected in multiple environmental matrices and their toxicological implications are increasingly reported. We herein investigated the antiandrogenic activities of eight BUVSs prior to and after human CYP3A4-mediated metabolic activation/deactivation by the two-hybrid recombinant human androgen receptor yeast bioassay and the in vitro metabolism assay. More potent antiandrogenic activity was observed for the metabolized UV-328 in comparison with UV-328 at 0.25 μM ((40.73 ± 4.90)% vs. (17.12 ± 3.00)%), showing a significant metabolic activation. In contrast, the metabolized UV-P at 0.25 μM resulted in a decreased antiandrogenic activity rate from (16.08 ± 0.95)% to (6.91 ± 2.64)%, indicating a metabolic deactivation. Three mono-hydroxylated (OH) and three di-OH metabolites of UV-328 were identified by ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS/MS), which were not reported previously. We further surmised that the hydroxylation of UV-328 occurs mainly at the alicyclic hydrocarbon atoms based on the in silico prediction of the lowest activation energies of hydrogen abstraction from C-H bond. Our results for the first time relate antiandrogenic activity to human CYP3A4 enzyme-mediated hydroxylated metabolites of BUVSs. The biotransformation through hydroxylation should be fully considered during the health risk assessment of structurally similar analogs of BUVSs and other emerging contaminants. [ABSTRACT FROM AUTHOR]

One of the major causes of significant crop loss throughout the world is the myriad of environmental stresses including drought, salinity, cold, heavy metal toxicity, and ultraviolet-B (UV-B) rays. Plants as sessile organisms have evolved various effective mechanism which enable them to withstand this plethora of stresses. Most of such regulatory mechanisms usually follow the abscisic-acid (ABA)-dependent pathway. In this review, we have primarily focussed on the basic leucine zipper (bZIP) transcription factors (TFs) activated by the ABA-mediated signalosome. Upon perception of ABA by specialized receptors, the signal is transduced via various groups of Ser/Thr kinases, which phosphorylate the bZIP TFs. Following such post-translational modification of TFs, they are activated so that they bind to specific cis-acting sequences called abscisic-acid-responsive elements (ABREs) or GC-rich coupling elements (CE), thereby influencing the expression of their target downstream genes. Several in silico techniques have been adopted so far to predict the structural features, recognize the regulatory modification sites, undergo phylogenetic analyses, and facilitate genome-wide survey of TF under multiple stresses. Current investigations on the epigenetic regulation that controls greater accessibility of the inducible regions of DNA of the target gene to the bZIP TFs exclusively under stress situations, along with the evolved stress memory responses via genomic imprinting mechanism, have been highlighted. The potentiality of overexpression of bZIP TFs, either in a homologous or in a heterologous background, in generating transgenic plants tolerant to various abiotic stressors have also been addressed by various groups. The present review will provide a coherent documentation on the functional characterization and regulation of bZIP TFs under multiple environmental stresses, with the major goal of generating multiple-stress-tolerant plant cultivars in near future. [ABSTRACT FROM AUTHOR]

Spectral solar UV radiation measurements are performed in France using three spectroradiometers located at very different sites. One is installed in Villeneuve d'Ascq, in the north of France (VDA). It is an urban site in a topographically flat region. Another instrument is installed in Observatoire de Haute-Provence, located in the southern French Alps (OHP). It is a rural mountainous site. The third instrument is installed in Saint-Denis, Réunion Island (SDR). It is a coastal urban site on a small mountainous island in the southern tropics. The three instruments are affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC) and carry out routine measurements to monitor the spectral solar UV radiation and enable derivation of UV index (UVI). The ground-based UVI values observed at solar noon are compared to similar quantities derived from the Ozone Monitoring Instrument (OMI, onboard the Aura satellite) and the second Global Ozone Monitoring Experiment (GOME-2, onboard the Metop-A satellite) measurements for validation of these satellite-based products. The present study concerns the period 2009-September 2012, date of the implementation of a new OMI processing tool. The new version (v1.3) introduces a correction for absorbing aerosols that were not considered in the old version (v1.2). Both versions of the OMI UVI products were available before September 2012 and are used to assess the improvement of the new processing tool. On average, estimates from satellite instruments always overestimate surface UVI at solar noon. Under cloudless conditions, the satellite-derived estimates of UVI compare satisfactorily with ground-based data: the median relative bias is less than 8% at VDA and 4% at SDR for both OMI v1.3 and GOME-2, and about 6% for OMI v1.3 and 2% for GOME-2 at OHP. The correlation between satellite-based and ground-based data is better at VDA and OHP (about 0.99) than at SDR (0.96) for both space-borne instruments. For all sky conditions, the median relative biases are much larger, with large dispersion for both instruments at all sites (VDA: about 12%; OHP: 9%; SDR: 11%). Correlation between satellite-based and ground-based data is still better at VDA and OHP (about 0.95) than at SDR (about 0.73) for both satellite instruments. These results are explained considering the time of overpass of the two satellites, which is far from solar noon, preventing a good estimation of the cloud cover necessary for a good modelling of the UVI. Site topography and environment are shown to have a non-significant influence. At VDA and OHP, OMI v1.3 shows a significant improvement with respect to v1.2, which did not account for absorbing aerosols. [ABSTRACT FROM AUTHOR]

Recent studies have found that solar ultraviolet ( UV) radiation significantly shifts the mass loss and nitrogen dynamics of plant litter decomposition in semi-arid and arid ecosystems. In this study, we examined the role of photodegradation in litter decomposition by using the DayCent- UV biogeochemical model. DayCent- UV incorporated the following mechanisms related to UV radiation: (1) direct photolysis, (2) facilitation of microbial decomposition via production of labile materials, and (3) microbial inhibition effects. We also allowed maximum photodecay rate of the structural litter pool to vary with litter's initial lignin fraction in the model. We calibrated DayCent- UV with observed ecosystem variables (e.g., volumetric soil water content, live biomass, actual evapotranspiration, and net ecosystem exchange), and validated the optimized model with Long-Term Intersite Decomposition Experiment ( LIDET) observations of remaining carbon and nitrogen at three semi-arid sites in Western United States. DayCent- UV better simulated the observed linear carbon loss patterns and the persistent net nitrogen mineralization in the 10-year LIDET experiment at the three sites than the model without UV decomposition. In the DayCent- UV equilibrium model runs, UV decomposition increased aboveground and belowground plant production, surface net nitrogen mineralization, and surface litter nitrogen pool, but decreased surface litter carbon, soil net nitrogen mineralization, and mineral soil carbon and nitrogen. In addition, UV decomposition had minimal impacts on trace gas emissions and biotic decomposition rates. The model results suggest that the most important ecological impact of photodecay of surface litter in dry grasslands is to increase N mineralization from the surface litter (25%), and decay rates of the surface litter (15%) and decrease the organic soil carbon and nitrogen (5%). [ABSTRACT FROM AUTHOR]

A new method for calculating the altitude UV dependence is proposed for different types of biologically active UV radiation (erythemally weighted, vitamin- D-weighted and cataract-weighted types). We show that for the specified groups of parameters the altitude UV amplification (AUV) can be presented as a composite of independent contributions of UV amplification from different factors within a wide range of their changes with mean uncertainty of 1% and standard deviation of 3% compared with the exact model simulations with the same input parameters. The parameterization takes into account for the altitude dependence of molecular number density, ozone content, aerosol and spatial surface albedo. We also provide generalized altitude dependencies of the parameters for evaluating the AUV. The resulting comparison of the altitude UV effects using the proposed method shows a good agreement with the accurate 8-stream DISORT model simulations with correlation coefficient r >0.996. A satisfactory agreement was also obtained with the experimental UV data in mountain regions. Using this parameterization we analyzed the role of different geophysical parameters in UV variations with altitude. The decrease in molecular number density, especially at high altitudes, and the increase in surface albedo play the most significant role in the UV growth. Typical aerosol and ozone altitude UV effects do not exceed 10-20%. Using the proposed parameterization implemented in the on-line UV tool (http://momsu.ru/uv/) for Northern Eurasia over the PEEX domain we analyzed the altitude UV increase and its possible effects on human health considering different skin types and various open body fraction for January and April conditions in the Alpine region. [ABSTRACT FROM AUTHOR]

The influence of UV-B irradiation on filtered and non-filtered water samples collected in a non-polluted area of Tagus estuary was evaluated in this study. In the laboratory, both samples were titrated with lead (Pb) followed by differential pulse anodic stripping voltammetry (DPASV), before and after 1 and 10 days under UV-B irradiation. Metal-ligand complexing parameters were obtained based on a macromolecular heterogeneous ligand described by two distinct sites with a labile behavior, and a third small homogeneous weaker group, which concentration was determined from a potentiometric titration. Under UV-B radiation, the complexing strength decreased with time in both (filtered and non-filtered) irradiated samples, but this effect was more pronounced in the non-filtered water, which might be due to some adsorption of dissolved macromolecular ligands on the particles and/or to further degradation of dissolved organic matter (DOM). Furthermore, the presence of particles favored the break-down of the macromolecular ligand under long UV-B exposure time. These results present ecological implications for the estuarine ecosystems such as bioavailability and toxicity. [ABSTRACT FROM AUTHOR]

Nanoparticles occurring in the environment originate either from engineered, synthetically produced nanoparticles, or from naturally produced nanoparticles. The latter can be formed in natural media by light-induced reduction of metal ions in presence of natural organic matter, such as humic substances occurring widely in waters, soils and sediments. There is actually few knowledge on the effect of sunlight and of the nature of organic matter on nanoparticle formation. Therefore, we studied here the photoreduction of silver(I) ion to silver nanoparticles with and without ferrous ion under oxic and anoxic conditions, using humic and fulvic acids as proxies of natural organic matter. UV light-induced formation of silver nanoparticles was monitored up to 60 min by measuring surface plasmon resonance in air-saturated mixture and nitrogen-saturated mixture of silver(I) ion-organic matter. Results show that the surface plasmon resonance intensity was about 2.5 times higher in the nitrogen-purged solution mixture than the air-saturated solution. This finding suggests the oxygen-containing species had no major role in forming silver nanoparticles. Therefore, photo-driven formation of silver nanoparticles most likely involved photoactivation of silver(I) ion and natural organic matter complexes. We observed also that both iron(II) and iron(III) ions highly modified the surface plasmon resonance spectra of the particles with broader features. Results also reveal that in the presence of humic acid, the intensity of the surface plasmon resonance peak decreased by at least 50 %, while almost no change in the intensity was seen when fulvic acid was used. Overall, our findings demonstrate that the ligand-metal charge transfer process, affected by the nature of organic matter, i.e., humic acid versus fulvic acid, was influenced by redox iron species. [ABSTRACT FROM AUTHOR]

Peatlands export significant amounts of dissolved organic carbon (DOC) to freshwaters, but the quantity of DOC reaching marine environments is typically less than the input to the fluvial system due to processing within the water column. Key removal processes include photo-chemical degradation, and heterotrophic bacterial respiration. In this study we examined these processes using C-labelled DOC to quantify the extent of DOC breakdown and to determine its fate following irradiation under controlled laboratory conditions. We examined the influence of microbial processes occurring within the water column, the potential role of stream-bed biofilms, and the possible modifying effects of downstream mixing, as DOC in water from the peatland encounters runoff from upland mineral soils ('Mountain'), nutrient-rich runoff from agricultural soils, and seawater in an estuary. Our results demonstrated conservative mixing of DOC from Peatland and Mountain waters but interactive effects when Peatland water was mixed with Agricultural and Estuary waters and exposed to solar radiation. The mixing of Peatland and Agricultural waters led to net DOC production, suggesting that DOC was only partially degraded by solar radiation and that the products of this might have fuelled autotrophic microbial growth in the samples. The mixing of Peatland water with saline estuary water resulted in net DOC loss following irradiation, suggesting a role for sunlight in enhancing the flocculation of DOC to particulate organic carbon (POC) in saline environments. [ABSTRACT FROM AUTHOR]

Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39–44°S) and in an Antarctic bay (62°S). Based on vertical diffuse attenuation coefficients (Kd), derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1%) in these water bodies ranged 2–11 m for UV-B (313 nm), 4–27 m for UV-A (395 nm), and 7–30 m for PAR (euphotic zone). UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica) exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter) characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal) variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be further exacerbated by cold temperatures in this location, together with episodes of ozone depletion. Overall, the results emphasize the marked spatial (horizontal and vertical) and temporal heterogeneity of optical characteristics, and challenges that these imply for estimations of underwater optics. [ABSTRACT FROM AUTHOR]

Environmental drivers such as climate change are responsible for extreme events that are critically altering freshwater resources across the planet. In the continental US, these events range from increases in the frequency and duration of droughts and wildfires in the West, to increasing precipitation and floods that are turning lakes and reservoirs brown in the East. Such events transform and transport organic carbon in ways that affect the exposure of ecosystems to ultraviolet ( UV) radiation and visible light, with important implications for ecosystem services. Organic matter dissolved in storm runoff or released as black carbon in smoke selectively reduces UV radiation exposure. In contrast, droughts generally increase water transparency, so that UV radiation and visible light penetrate to greater depths. These shifts in water transparency alter the potential for solar disinfection of waterborne parasites, the production of carcinogenic disinfection byproducts in drinking water, and the vertical distribution of zooplankton that are a critical link in aquatic food webs. [ABSTRACT FROM AUTHOR]

Ultraviolet-B (UV-B) radiation exposure is one hypothesized mechanism explaining amphibian population declines and malformations, but it is rarely quantified in amphibian habitats. We measured spatial and temporal variations in northern vernal pools with UV-B attenuation through the water column, incident UV-B across pool surfaces and seasons, and cumulative UV-B dose. Atmospheric, local, and landscape effects were compared with variances across spatial and temporal scales, plus influence on exposure risk. Risk was evaluated using published reports on detrimental levels for amphibian survival and health, with life history and behavior of vernal pool breeding Rana sylvatica L. (wood frog). Pools were exposed to sufficiently high UV-B at or near the surface for developing amphibians to be at risk of reduced survival, altered growth, and malformation. Atmospheric conditions, vegetative cover, and water column properties significantly influenced UV-B levels, with oviposition and larval behavior controlling actual embryonic and larval exposure. UV-B risk to vernal pool species is greater than predicted in previous studies. Given changes in light regimes, climate change, and forest harvesting, amphibian UV-B exposure could reach levels of great concern. Si l'exposition au rayonnement ultraviolet B (UV-B) est un des mecanismes postules pour expliquer le declin des populations et les malformations observees chez les amphibiens, la quantification de cet effet dans des habitats d'amphibiens est rare. Nous avons mesure les variations spatiales et temporelles dans des etangs vernaux nordiques associees a l'attenuation du rayonnement UV-B dans la colonne d'eau, a la distribution de l'UV-B a la surface des etangs et aux saisons, ainsi que la dose cumulative d'UV-B. Les effets atmospheriques, locaux et du paysage ont ete compares aux variances a differentes echelles spatiales et temporelles, en plus de l'influence sur le risque d'exposition. Le risque a ete evalue a la lumiere de rapports publies sur les niveaux nuisibles a la survie et a la sante des amphibiens, pour le cycle de vie et le comportement de Rana sylvatica L. (grenouilles des bois) se reproduisant en etang vernal. Les etangs etaient exposes a un UV-B suffisamment eleve a la surface ou pres de celle-ci pour poser un risque de reduction du taux de survie, de modification de la croissance et de malformation des amphibiens en developpement. Les conditions atmospheriques, la couverture vegetale et les proprietes de la colonne d'eau exercaient une influence significative sur les niveaux d'UV-B, l'exposition reelle des embryons et des larves etant controlee par l'oviposition et le comportement des larves. Le risque que presente l'UV-B pour les especes d'etang vernal est plus grand que ce qu'avaient predit des etudes anterieures. Dans un contexte de rayonnement lumineux variable, de changements climatiques et d'exploitation forestiere, l'exposition des amphibiens au rayonnement UV-B pourrait atteindre des niveaux tres preoccupants., Introduction Amphibian populations are declining worldwide, with species becoming extinct or threatened on almost every continent in both disturbed and pristine areas (Stuart et al. 2004; IUCN 2008). In addition [...]

This study investigates different UV doses (mJ/cm 2 ) and the effect of dark incubation on the survival of the algae Tetraselmis suecica , to simulate ballast water treatment and subsequent transport. Samples were UV irradiated and analyzed by flow cytometry and standard culturing methods. Doses of ≥ 400 mJ/cm 2 rendered inactivation after 1 day as measured by all analytical methods, and are recommended for ballast water treatment if immediate impairment is required. Irradiation with lower UV doses (100–200 mJ/cm 2 ) gave considerable differences of inactivation between experiments and analytical methods. Nevertheless, inactivation increased with increasing doses and incubation time. We argue that UV doses ≥ 100 mJ/cm 2 and ≤ 200 mJ/cm 2 can be sufficient if the water is treated at intake and left in dark ballast tanks. The variable results demonstrate the challenge of giving unambiguous recommendations on duration of dark incubation needed for inactivation when algae are treated with low UV doses. [ABSTRACT FROM AUTHOR]

Satellite observations of the ultraviolet aerosol index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOSChem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The inclusion of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after including BrC in the model is broadly consistent with reported observations for biomass burning aerosol, with absorbing Ångström exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 30% over South America in September, up to 20% over southern Africa in July, and up to 15% over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years, thus reducing the bias against observed values. We calculate the direct radiative effect (DRE) of BrC using GEOS-Chem coupled with the radiative transfer model RRTMG (GC-RT). Treating organic aerosol as containing more strongly absorbing BrC changes the global annual mean all-sky top of atmosphere (TOA) DRE by +0.03 W m-2 and all-sky surface DRE by -0.08 W m-2. Regional changes of up to +0.3 W m-2 at TOA and down to -1.5 W m-2 at the surface are found over major biomass burning regions. [ABSTRACT FROM AUTHOR]

Increase in ultraviolet radiation (UVR) due to stratospheric ozone depletion on the earth surface poses threat to plants and animals. Zooplankton live near water surfaces thus increases their chances of exposure to UVR. Many negative effects of UVR have been reported on zooplankton communities. In this study, effect of solar and artificial UV-B with temperature was studied on the cladocera and copepod thus indicating their sensitivity towards UVR. Daphnia from Cladocera and Cyclops from Copepoda were taken as test organisms. Exposure of solar and UV radiations was given two hours each for 15 days. The experiment was conducted at high and low temperature to record the effect of temperature on UV response of Daphnia and Cyclops. Daphnia showed higher mortality (22.97%) at high temperature than Cyclops (16.99%). At low temperature, Daphnia and Cyclops showed low mortality i.e. 18.84% and 14.67% respectively. The results indicated that temperature increases the phototoxic effect of ultraviolet radiation on Daphnia and Cyclops. Daphnia showed more photosensitivity towards UVR at high temperature than Cyclops. Intensity dependent increase in mortality of Daphnia and Cyclops was observed. Enhancement of UV-B radiation due to ozone depletion and increase in temperature due to climate change may lead to significant change in zooplankton communities, aquatic biodiversity and ecosystem productivity. [ABSTRACT FROM AUTHOR]

Some of the most important effects of global change on coastal marine systems include increasing nutrient inputs and higher levels of ultraviolet radiation (UVR, 280–400 nm), which could affect primary producers, a key trophic link to the functioning of marine food webs. However, interactive effects of both factors on the phytoplankton community have not been assessed for the Mediterranean Sea. An in situ factorial experiment, with two levels of ultraviolet solar radiation (UVR+PAR vs. PAR) and nutrients (control vs. P-enriched), was performed to evaluate single and UVR×P effects on metabolic, enzymatic, stoichiometric and structural phytoplanktonic variables. While most phytoplankton variables were not affected by UVR, dissolved phosphatase (APAEX) and algal P content increased in the presence of UVR, which was interpreted as an acclimation mechanism of algae to oligotrophic marine waters. Synergistic UVR×P interactive effects were positive on photosynthetic variables (i.e., maximal electron transport rate, ETRmax), but negative on primary production and phytoplankton biomass because the pulse of P unmasked the inhibitory effect of UVR. This unmasking effect might be related to greater photodamage caused by an excess of electron flux after a P pulse (higher ETRmax) without an efficient release of carbon as the mechanism to dissipate the reducing power of photosynthetic electron transport. [ABSTRACT FROM AUTHOR]

UVA radiation (320–400 nm) is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydrogen peroxide (H2O2), which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1) to several hours (replication fork velocity and origin firing). The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen. [ABSTRACT FROM AUTHOR]

The effects of increased photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic activity were studied in fast ice algal communities. The experimental set-up consisted of nine 1.44 m2 squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free ice covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic activity was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea ice, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic activity and community composition. [ABSTRACT FROM AUTHOR]

The integration of plant and Earth sciences offers the opportunity to develop and test palaeobotanical monitors and recorders (palaeoproxies) of past atmospheric change that are understood from a mechanistic perspective, with the underpinning responses being identified and understood at the genetic level. This review highlights how this approach has been used to deliver two distinct palaeoproxies. The first is based on the negative relationship between stomata (breathing pores found on the leaf surface) and atmospheric CO2 concentration; the second is based on tracking chemical changes seen in the composition of pollen and spores to reconstruct changes in the flux of UV-B radiation on the Earth's surface and from this infer changes in stratospheric processes linked to the eruption and emplacement of Large Igneous Provinces. Here, we highlight the potential of integrating a new rapid, inexpensive chemical analysis technique with existing, robust palynological methods, opening the door to a deeper understanding of past environments via the palaeobiological record. A look to the future suggests a combined solar radiation- CO2 concentration approach could be readily applied across the geological record. [ABSTRACT FROM AUTHOR]

Stellar occultations of the Saturn atmosphere using the Cassini ultraviolet imaging spectrograph (UVIS) experiment have provided vertical structure at a range of latitudes. The transmission spectra in the extreme-far ultraviolet (EUV-FUV) range allow extraction of vertical profiles of [H.sub.2] and hydrocarbon abundances from the top of the atmosphere to about 300 km above the 1 bar (1 bar = 100 kPa) pressure level. A reanalysis of the Voyager 2 δSco occultation in 1981 is consistent with the original report. The hydrocarbon homopause is near a pressure of 0.2 µbar in the UVIS analysis, compared to ~0.01 µbar obtained from the Voyager occultation. Measured hydrocarbon abundances are obtained in the pressure range 600-0.1µbar in the Cassini UVIS experiment. The combined UVIS results provide evidence for significant latitudinal dependence of vertical temperature profile. The confinement of the hydrocarbons in the current observations compared to published models and the Voyager ultraviolet spectrograph (UVS) results at solar maximum, infer smaller eddy diffusion coefficients in this epoch. Model calculations indicate that the latitudinal dependence of [H.sub.2] vertical displacements is caused primarily by the combined effects of gravitational potential and evident differences in electron energy deposition at the top of the atmosphere affecting the temperature profile. The derived [H.sub.2] density profiles from ~-40° latitude and others close to the equator, are found to be nearly identical on a pressure scale below the exobase. The inference is that that the pressure profile of [H.sub.2] density at Saturn is unchanged over a broad range of latitudes. PACS Nos.: 96., 96.12.jt, 96.12.Ma, 96.30.Mh En utilisant le spectrographe ultraviolet a image Cassini (UVIS), les occultations solaires de l'atmosphere de Saturne ont fourni la structure verticale pour une gamme de latitude. Les spectres en transmission dans le domaine EUVFUV permettent d'extraire les profiles verticaux d'abondance en [H.sub.2] et en hydrocarbures a partir de la partie superieure de l'atmosphere jusqu'a environ 300 km du niveau de pression de 1 bar (1 bar = 100 kPa). Une reanalyse des occultations δSco de Voyager 2 en 1981 est coherente avec le rapport initial. L'homopause des hydrocarbures est proche du niveau de 0.2 µbar dans l'analyse UVIS, mais plus pres du niveau de 0.01 µbar a dans l'occultation de Voyager. Cassini mesure les abondances d'hydrocarbures dans une gamme allant de 600 a 0.1 µbar. Les resultats combines de UVIS indiquent une nette dependance en latitude du profile vertical de temperature. Le confinement des hydrocarbures dans les mesures recentes, comparees a celles de modeles recents et a celles de Voyager prises lors d'un maximum solaire, suggerent un plus faible coefficient de turbulence a notre epoque. Des modelisations numeriques indiquent que la dependance en latitude des deplacements verticaux de [H.sub.2] est causee surtout par l'effet combine du potentiel gravitationnel et une difference evidente de la deposition en energie par les electrons a la partie superieure de l'atmosphere, ce qui affecte le profile de temperature. Les profiles de densite de [H.sub.2] obtenus entre ~-40° de latitude et d'autres pres de l'equateur sont pratiquement identiques a une echelle de pression sous l'exobase. Nous en concluons que le profile en pression de la densite de [H.sub.2] dans l'atmosphere de Saturne reste inchange sur un large domaine de latitudes. [Traduit par la Redaction], 1. Introduction Results from the Cassini UVIS experiment occultation probes of the vertical structure of the Saturn atmosphere are described in this work. The analysis of stellar occultations are targeted. [...]

This paper presents a new calculation of neutral gas heating by solar extreme ultraviolet and ultraviolet radiation with updated solar irradiances and photochemistry. It is found that the heating rate of the neutral gas is significantly different from some previous determinations. Neutral gas heating arises from the many exothermic chemical reactions that take place from the ions and excited species created by energetic electrons. The calculations show that less than half the energy initially deposited ends up heating the neutral gases. The rest is radiated or lost in the dissociation of [O.sup.2] because the O atoms do not recombine in the thermosphere above 100 km. At high altitudes, the heating rates are sensitive to the thermal electron density and long-lived species. The calculations show that, while most of the energy is deposited at low altitudes, the heating per neutral particle is greatest at high altitudes. This paper also examines the consequences of different thermal electron cooling rates to [O.sup.2] vibration and O fine structure. Although there are large differences between the individual rates, the overall cooling rates have similar magnitudes and there is little effect on the calculated electron temperature. The concept of the neutral gas heating efficiency is a useful way of capturing the flow of energy in the thermosphere and was used in early global models to reduce computation. It is defined at a particular altitude as the rate of energy transferred to the neutral gas divided by the energy deposited rate at that altitude. The heating efficiency peaks at about 0.5 just below 200 km altitude. The heating efficiency is relatively insensitive to the solar input and thermosphere conditions when plotted against pressure rather than altitude coordinates and when thermal electron heating is calculated separately. PACS Nos.: 94.20.Cf, 94.20.D-, 94.20.dj, 94.20.dm, 94.20.dv Nous presentons ici les resultats du calcul de rechauffement du gaz neutre par la radiation EUV et UV solaire, en tenant compte des nouvelles donnees d'irradiance et de photochimie. Nous trouvons que le taux de rechauffement du gaz neutre differe significativement des resultats anterieurs. Ce rechauffement provient de plusieurs reactions exothermiques entre les ions et les especes chimiques excitees par les electrons energetiques. Le calcul montre que moins de la moitie de l'energie deposee contribue au rechauffement du gaz neutre. Le reste est irradie ou perdu dans la dissociation du [O.sub.2,] parce que les atomes de O ne se recombinent pas dans la thermosphere au dessus de 100 km. A haute altitude, les taux de rechauffement sont sensibles a la densite d'electrons thermiques et des especes stables. Les calculs montrent qu'alors que la majorite de l'energie est deposee a basse altitude, le rechauffement par particule neutre est plus important a haute altitude. Nous examinons aussi les consequences de differents taux de refroidissement des electrons thermiques sur les vibrations de [O.sub.2] et la fine structure de O. Meme si les taux individuels different beaucoup, les taux de refroidissement restent globalement du m&rie ordre de grandeur et il y a peu d'effet sur la temperature calculee pour les electrons. Le concept d'efficacite de rechauffement du gaz neutre est pratique pour decrire la capture du flux d'energie dans la thermosphere et a ete utilise des les premiers modeles, afin de minimiser la lourdeur des calculs. Il est defini a une atmosphere donnee comme le taux d'energie transferee au gaz neutre, divise par le taux d'energie deposee a cette altitude. L'efficacite de rechauffement a un pic d'environ 0.5 autour de 200 km d'altitude. Elle est relativement insensible a l'intrant solaire et aux conditions de la thermosphere lorsque etudiee en fonction de la pression plutot que de l'altitude et lorsque le rechauffement des electrons thermiques est calcule separement. [Traduit par la Redaction], 1. Introduction Solar radiation is the primary source of thermospheric heating through ionization, excitation, and dissociation of the ambient neutral gases. For the purpose of the analysis, the solar spectrum [...]

Sunlight is required for vital biological processes. However, solar ultraviolet radiation can have a detrimental impact on living organisms, by acting as a natural mutagenic agent. With this activity, intended for middle school and high school, we propose a simple hands-on experiment to investigate the bactericidal effect of sunlight. The activity provides appealing visual results and opportunities for extension of inquiry. Procedural instructions, discussion topics, and assessment suggestions are detailed. Key Words: Bacteria; DNA; mutation; science experiment; sunlight; ultraviolet radiation., Sunlight is essential for vital biological processes, such as photosynthesis and vitamin D synthesis. However, solar ultraviolet (UV) radiation can be detrimental to living beings: it is associated with coral [...]

Doi: 10.1080/10473289.2011.599271 There is a growing recognition of the risks to health, fire hazard, and air quality from cooking emissions. Recent research has identified what is emitted when foods are [...]

Increasing UV-B radiation (UV-B; 290-320 nm) due to stratospheric ozone depletion has been a leading explanation for the decline in amphibians for nearly 2 decades. Yet, the likelihood that UV-B can influence amphibians at the large spatial scales relevant to population declines has not yet been evaluated. A key limitation has been in relating results from individual sites to the effect of UV-B for populations distributed across heterogeneous landscapes. We measured critical embryonic exposures to UV-B for two species of montane amphibians with contrasting physiological sensitivities, long-toed salamander (Ambystoma macrodactylum) and Cascades frog (Rana cascadae), at field sites spanning a gradient of UV-B attenuation in water. We then used these experimental results to estimate the proportion of embryos exposed to harmful UV-B across a large number of breeding sites. By combining surveys of the incubation timing, incident UV-B, optical transparency of water, and oviposition depth and light exposure of embryos at each site, we present a comprehensive assessment of the risk posed by UV-B for montane amphibians of the Pacific Northwest. We found that only 1.1% of A. macrodactylum and no R. cascadae embryos across a landscape of breeding sites are exposed to UV-B exceeding lethal levels. These results emphasize that accurately estimating the risk posed by environmental stressors requires placing experimental results in a broader ecological context that accounts for the heterogeneity experienced by populations distributed across natural landscapes. amphibian declines | ultraviolet radiation | risk analysis | dissolved organic matter | oviposition behavior www.pnas.org/cgi/doi/10.1073/pnas.0912970107