Lethal and mutational effects of solar and UV radiation on Staphylococcus aureus

Strains of Staphylococcus aureus, an opportunistic pathogen commonly found on human skin, were exposed to sunlight and UV C radiation, and the lethal and mutational effects measured. Sunlight killed cells with an inactivation constant of 3×10^-5 per joule per square metre; UV C was much more lethal, giving an inactivation constant of approximately 0.1 per joule per square metre. Some strains tested showed a sensitivity to sunlight that was dependent on the growth phase of the cells, exponentially growing cells showing a greater sensitivity. Mutational effects of irradiation were measured by the appearance of mutants sensitive to methicillin following irradiation of a multiresistant strain. Mutants appeared at a frequency of 10^-3; this high frequency of mutation in the region of the mec gene has also been observed when multiresistant strains are subjected to nutritional or thermal stress. Mutants showed the same chromosomal alteration (seen in pulse-field gel electrophoresis of Smal-digested DNA) whether induced by solar or UV C irradiation.     

Influence of solar ultraviolet radiation on photosynthesis and motility of marine phytoplankton

Abstract: The effects of solar ultraviolet radiation (UV) on carbon uptake, oxygen evolution and motility of marine phytoplankton were investigated in coastal waters at Kristineberg Marine Research Station on the west coast of Sweden (58° 30'N, 11° 30'E). The mean irradiances at noon above the water surface during the investigation period were: photosynthetic active radiation (PAR, 400–700 nm) 1670 μmol m⁻² s⁻¹; ultraviolet-A radiation (UV-A, 320–400 nm) 35.9 W m⁻² and ultraviolet-B radiation (UV-B, 280–320 nm) 1.7 W m⁻². UV-B radiation was much more attenuated with depth in the water column than were PAR and UV-A radiation. UV-B radiation could not be detected at depths greater than 100–150 cm. Inhibition of carbon uptake by UV-A and UV-B in natural phytoplankton populations was greatest at 50 cm depth and the effects of UV-B were greater than those of UV-A. At depths greater than 50 cm there was almost no effect of ultraviolet radiation on carbon uptake. PAR, UV-A and UV-B decreased oxygen evolution by the dinoflagellate Prorocentrum minimum . Inhibition of oxygen evolution was greater after 4 h than 2 h but it was not possible to distinguish the negative effects of the different light regimes. The motility of P. minimum was not affected by PAR, UV-A and UV-B. The importance of exposure of phytoplankton to different light regimes before being exposed to natural solar radiation is discussed.     

Effect of solar ultraviolet radiation on growth in the marine macroalga Dictyota dichotoma (Phaeophyceae) at Helgoland and its ecological consequences

At Helgoland, in the North Sea, growth of the high sublittoral brown macroalga Dictyota dichotoma (Hudson) Lamoroux was examined in October (the time of tetraspore release) in an outdoor tank by exposing 2-day-old germlings to four solar radiation treatments achieved with different filter materials or an additional artificial light source: photosynthetically active radiation (PAR; 395–700 nm), PAR plus ultraviolet (UV)-A (320–700 nm), full solar spectrum, or solar spectrum plus artificial UV radiation (UVR). Based on length measurements over a period of 3 weeks, the growth rate in germlings strongly decreased in conditions with UVR compared to PAR: by 14% under PAR+UV-A, by 31% under the full solar spectrum and by 65% with additional UVR. Although growth rates of germlings under UVR were reduced mainly in the first week, the plants did not regain the size of the untreated plants even after 9 weeks. Regardless of the exposure, no defects in morphology or anatomy including the exposed apical meristem were detected, except for a reduction in cell division rates perhaps due to additional cost for photoprotective or repair mechanisms. Depending on the actual position of D. dichotoma plants in the natural habitat, individuals in high positions receive substantial amounts of the more harmful UV-B while those lower down might only receive UV-A during part of the day, thus the effect of UV-B on the growth of D. dichotoma will depend on its position in the field. The effects of tidal variation of the light climate and the implications of our results for the zonation of D. dichotoma are discussed. Received in revised form: 6 July 2000 Electronic Publication     

Motility and orientation of a dinoflagellate, Gymnodinium, impaired by solar and ultraviolet radiation

Abstract The effects of solar and artificial ultraviolet radiation on the motility and orientation of the dinoflagellate Y-100 were studied. The cells show a weak photokinesis but a pronounced phototaxis which is consistently positive between 1 and 100 klx (= 4 mW m⁻² to 400 mW m⁻²); the precision of orientation increases with the fluence rate. Unfiltered solar radiation as well as artificial ultraviolet radiation reduce the percentage of motile cells increasingly with exposure time but the velocity of the still motile cells is less affected. Unirradiated control cells show a negative gravitaxis. After short exposure to solar or artificial ultraviolet radiation the precision of gravitaxis decreases and after prolonged exposure the cells start to actively move downward in the water column (positive gravitaxis). Phototaxis is also strongly impaired by ultraviolet radiation.     

Effects of solar radiation and solar radiation deprived of UV-B and total UV on photosynthetic oxygen production and pulse amplitude modulated fluorescence in the brown alga Padina pavonia

Abstract: The effects of solar radiation on photosynthetic oxygen production and pulse amplitude modulated (PAM) fluorescence were measured in the marine brown macroalga Padina pavonia harvested from different depths from the Greek coast near Korinth. In fluence rate-response curves the light compensation point for photosynthetic oxygen production increased and the saturation level decreased with increasing exposure time to solar radiation. Cutting off the UV-B wavelength range (280–315 nm) from solar radiation reduced the inhibition of photosynthesis, and the organisms were less affected when all of the UV radiation was filtered out. Algae collected from 7 m depth were much more prone to photoinhibition than those harvested from rock pools exposed to unfiltered solar radiation. During continuous exposure to solar radiation, rock pool algae showed photoinhibition after longer periods of time than specimens from 7 m or from dark adapted habitats. When subjected to unfiltered solar radiation the ratio of the variable fluorescence to the maximal fluorescence     (F_v = F_m− F_o) rapidly declined with increasing exposure time. However, again algae from 7 m depth were more prone to photoinhibition than rock pool algae. The differences between the two ecological strains were less obvious when UV-B or total UV was removed from solar radiation. Only in the latter case a complete recovery was observed after 2 h while, when exposed to unifiltered sunlight, only the rock pool algae recovered completely within that time.     

Penetration and effects of solar UV-B on phytoplankton and macroalgae

The effects of short wavelength solar radiation on aquatic ecosystems were studied in several marine and freshwater systems. The spectral distribution and the penetration of solar radiation into different water types (coastal and oceanic waters of the Baltic Sea, North Sea, Atlantic and Mediterranean) were investigated. Penetration of short wavelength solar radiation strongly depends on the content of dissolved and particulate substances as well as the concentration of phytoplankton. The primary producers often show a typical vertical distribution within the euphotic zone and are reached as well as affected by the penetrating UV-B radiation. The effect of this radiation was both determined in phytoplankton and macroalgae. Measuring pulse amplitude modulated (PAM) fluorescence indicated that major biomass producers were severely inhibited by surface radiation and even impaired at their natural growth site. Likewise, photosynthetic oxygen production was affected by extended exposure to solar radiation.     

作物对太阳紫外线辐射增加的生物效应及其评估

作物对太阳紫外线辐射增加的生物效应及其评估郑有飞,杨志敏,颜景义,万长建（南京气象学院,南京２１００４４）Ｂｉｏｌｏｇｉｃａｌｒｅｓｐｏｎｓｅｏｆｃｒｏｐｓｏｎｅｎｈａｎｃｅｄｓｏｌａｒｕｌｔｒａｖｉｏｌｅｔｒａｄｉａｔｉｏｎａｎｄｉｔｓｅｓｔｉｍａ...     

Effects of solar and ultraviolet radiation on motility, photomovement and pigmentation in filamentous, gliding cyanobacteria

Abstract The effects of solar irradiation and artificial UV irradiation on several cyanobacteria ( Anabaena variabilis and two strains of Phormidium uncinatum ) have been studied. Both types of radiation affect the percentage of motile filaments and impair the linear velocity of the organisms. Long term exposure to UV radiation bleaches the photosynthetic pigments as determined by absorption difference spectra. Fluorescence excitation and emission spectra indicate that under ultraviolet radiation the energy transfer from the accessory pigments to chlorophyll is affected. Furthermore the structural integrity of the phycobilisomes seems to be impaired by continuous radiation and the photoreceptor pigments seem to be destroyed.     

Inhibition of phytoplankton photosynthesis by solar ultraviolet radiation: studies in Lake Titicaca, Bolivia

1. Lake Titicaca is a large, high altitude (3810 m a.s.l.) tropical lake (16°S, 68°W) that lies on the border of Bolivia and Perú, receiving high fluxes of ultraviolet radiation (UVR) throughout the year. Our studies were conducted during September of 1997 with the main objective of studying the impact of solar UVR upon phytoplankton photosynthesis.
2. Water samples were taken daily and incubated in situ (down to 14 m depth) under three radiation treatments to study the relative responses to PAR (Photosynthetic Available Radiation, 400–700 nm), UV-A (320–400 nm), and UV-B (280–320 nm) radiation.
3. Photosynthetic inhibition by UVR in surface waters was about 80%, with UV-A accounting for 60% and UV-B for 20%; the inhibition by high levels of PAR was less than 20%. The inhibition due to UVR decreased with depth so that there were no significant differences between treatments at 8.5 m depth.
4. The amount of inhibition per unit energy received by phytoplankton indicates that even though there was a significant inhibition of photosynthesis due to UVR, species in Lake Titicaca seem to be better adapted than species in high latitude environments.
5. The cellular concentration of UV-absorbing compounds, a possible mechanism of photoadaptation, was low in phytoplanktonic species. However, they were abundant in zooplankton, suggesting a high rate of bioaccumulation through the diet.     

Effects of artificial and solar UV-B radiation on the gravitactic orientation of the dinoflagellate, Peridinium gatunense

Abstract The effects of artificial and solar UV-B radiation on the gravitactic (formerly called geotactic) orientation of the freshwater dinoflagellate Peridinium gatunense were measured under artificial UV-B radiation and in a temperature-controlled growth chamber under solar radiation in Portugal. Circular histograms of gravitaxis show the impairement of orientation after UV irradiation. The degree of orientation, quantified using the Rayleigh test and top quadrant summation, decreased as the exposure time to the radiation prolonged. The effects of artifical UV-B radiation on orientation are stronger than those of solar radiation, probably because the radiation source emits higher fluence rates below 300 nm than found in solar radiation. After UV radiation, the gravitactic orientation under artificially increased acceleration at 2 g was drastically affected.     

Effect of solar ultraviolet radiation on survival of krill larvae and copepods in Antarctic Ocean

The effect of solar ultraviolet radiation on the survival rate of Antarctic zooplankton was examined in February–March in 2002. We investigated survival rate of calyptopis larvae of Euphausia superba and late copepodite stages (IV and V) of large dominant calanoid species, Calanoides acutus and Calanus propinquus reared in quartz jars with three different radiation regimes (total radiation, exclusion of UVB, exclusion of UVA and UVB) and a dark control. The survival rates of the krill larvae decreased after 3 days from start of the experiment, being below 50% at 4 days in the treatments with total radiation and exclusion of UVB, although most individuals could survive until the end of the experiments in the treatments with exclusion of both UVA and UVB and dark control. The calanoid juveniles showed almost same pattern of survival curves as the krill larvae did, but survived slightly longer. Although >10% of surface UVA radiation at 340 and 380 nm penetrated down to 30 m, both C. acutus and C. propinquus were mostly distributed above 20 m. Surface swarm of the krill larvae can be often recognized in the previous studies. These results suggest that not only solar UVB but also UVA radiation potentially lower the survival rate of Antarctic zooplankton at depth less than 20 m.     

Childhood exposure to ultraviolet radiation and harmful skin effects: epidemiological evidence

We review the general amount and patterns of exposure to solar ultraviolet (UV) radiation that children and teenagers experience and the spectrum of UV-related skin damage that can occur as a result. Data about the amount of solar UV received by children and teenagers are relatively few but suggest that around 40–50% of total UV to age 60 occurs before age 20. Among white children, those with the palest complexions suffer the most damage. Comparisons of prevalence and incidence of outcomes in children and teenagers sharing common ancestry, but living at different latitudes, show that prevalence rates of photoaging and melanocytic naevi are higher in Australian compared with British children, and similarly for melanoma. Genetic risk for the majority of the melanomas in teens is a function of genes controlling naevus propensity and pigmentation in the skin. High numbers of naevi and freckles, red hair, blue eyes, inability to tan, as well as a family history are the primary determinants of melanoma among adolescents. Beyond the signs of skin damage seen in children are the latent effects observed later in adulthood. Childhood is believed to be a susceptible window for long-term harmful effects of UV, as evidenced by clear differences in skin cancer risk between child and adult migrants from high to low latitudes. Effective UV radiation protection from childhood is necessary to control both immediate and long-term harmful effects on children’s skin.     

The effects of solar radiation on thermal comfort

The aim of this study was to investigate the relationship between simulated solar radiation and thermal comfort. Three studies investigated the effects of (1) the intensity of direct simulated solar radiation, (2) spectral content of simulated solar radiation and (3) glazing type on human thermal sensation responses. Eight male subjects were exposed in each of the three studies. In Study 1, subjects were exposed to four levels of simulated solar radiation: 0, 200, 400 and 600 Wm⁻². In Study 2, subjects were exposed to simulated solar radiation with four different spectral contents, each with a total intensity of 400 Wm⁻² on the subject. In Study 3, subjects were exposed through glass to radiation caused by 1,000 Wm⁻² of simulated solar radiation on the exterior surface of four different glazing types. The environment was otherwise thermally neutral where there was no direct radiation, predicted mean vote (PMV)=0±0.5, [International Standards Organisation (ISO) standard 7730]. Ratings of thermal sensation, comfort, stickiness and preference and measures of mean skin temperature (t_sk) were taken. Increase in the total intensity of simulated solar radiation rather than the specific wavelength of the radiation is the critical factor affecting thermal comfort. Thermal sensation votes showed that there was a sensation scale increase of 1 scale unit for each increase of direct radiation of around 200 Wm⁻². The specific spectral content of the radiation has no direct effect on thermal sensation. The results contribute to models for determining the effects of solar radiation on thermal comfort in vehicles, buildings and outdoors.     

The effects of ultraviolet radiation on the planktonic community of a shallow, eutrophic estuary: results of mesocosm experiments

This paper describes the results of pelagic mesocosm experiments designed to test the effects of enhanced and reduced ultraviolet radiation (UV) on the planktonic community of a Baltic Sea estuary. The Darss-Zingst estuary consists of a series of brackish lagoons with high concentrations of chlorophyll and dissolved organic matter. The shallow depth of the estuary ensures that organisms in the water are regularly exposed to high levels of photosynthetically active radiation (PAR) and UV. During the summer of 1995 and 1996, four 1-m³ mesocosms were filled with water from the mid-point of the estuary. Each compartment was equipped with a pump to simulate natural rates of wind-induced vertical mixing. The mesocosms were hung in the estuary from a floating raft and were shielded from above by filters to give the spectral treatments PAR only, PAR+UV-A, and PAR+UV-A+UV-B. Enhanced levels of UV-B, i.e. twice that of midday sunlight, were provided in a further treatment by artificial sunlamps. Experiments were conducted for periods of 3–14 days. No significant effects of enhanced or reduced UV-B were observed on chlorophyll a concentrations or photosynthetic performance, although the PAR-only treatment did show higher final chlorophyll concentrations in two of the trials. Phytoplankton pigment composition was measured by in vivo absorption and fluorescence excitation spectra, and was similar in all mesocosm treatments indicating that there were no major differences in functional group composition. Bacterial secondary production rates as measured by thymidine incorporation increased with time in all mesocosms, probably due to enhanced production of phytoplankton exudate. There was evidence for a small depression of secondary production by enhanced UV-B, but only on certain days. Microzooplankton generally increased in all mesocosms to population densities higher than those observed in the estuary, and tended to reach higher final values in the mesocosms exposed to UV. It is concluded that vertical mixing which reduces the residence time of planktonic organisms in the surface layers, and high concentrations of chromophoric, dissolved organic matter, which greatly reduce the penetration of UV-B, combined to protect the planktonic community from UV-B damage. Received in revised form: 5 June 2000 Electronic Publication     

Sublethal effects of ultraviolet radiation on crab larvae of Cyrtograpsus altimanus

Ultraviolet radiation (UVR, 280-400 nm) is known to be lethal to several aquatic species; however, more subtle, ‘sublethal’ effects of UVR have recently received more attention. Larvae of the crab Cyrtograpsus altimanus are a transient component of the plankton community in the Atlantic northern Patagonia (Argentina) and thus they may be exposed to solar UVR in both open and coastal waters. The aim of this study was to determine if previous sublethal UVR exposure on larvae of C. altimanus affects development, body size and motility. Larvae which were pre-exposed to UVR had a delay/absence of molting from Zoea I to Zoea II, coupled to arrested body growth, but showed enhanced swimming behavior. In contrast, the control group (i.e., exposed only to visible light) molted from Zoea I to Zoea II after 6-9 days, with a significant increase in body size, and did not change their motility. Since hatching of this species occurs in summer (i.e., season with highest UVR levels) our results suggest that, by significantly affecting development, growth and motility, natural UVR may influence the plankton-benthos coupling in coastal waters.     

Adverse effects of ultraviolet radiation: a brief review

Solar ultraviolet radiation (UVR) has always been part of the environment of man. UVB is required for the conversion of 7-deoxycholesterol to vitamin D, which is critically important in the maintenance of healthy bones and research is making clear that it has other potential roles in maintenance of human health. Exposure to UVR, whether of solar or artificial origin, also carries potential risks to human health. UVR is a known carcinogen and excessive exposure-at least to solar radiation in sunlight-increases risk of cancer of the lip, basal cell, and squamous cell carcinoma of the skin and cutaneous melanoma, particularly in fair skin populations. There is also evidence that solar UVR increases risk of several diseases of the eye, including cortical cataract, some conjunctival neoplasms, and perhaps ocular melanoma. Solar UVR may also be involved in autoimmune and viral diseases although more research is needed in these areas. Artificial UVR from tanning beds, welding torches, and other sources, may contribute to the burden of disease from UVR. This brief review will assess the human evidence for adverse health effects from solar and artificial UVR and will attempt to assign a degree of certainty to the major disease-exposure relationships based on the weight of available scientific evidence.     

紫外B辐射增强对植食性昆虫的影响

大气平流层臭氧的破坏直接增强了到达地面的太阳紫外线,特别是紫外B辐射的强度。紫外B辐射增强将对生态系统产生深刻的影响。本文综述了近年来紫外B辐射增强对昆虫影响的研究,分析了紫外B辐射增强可能产生的对植食性昆虫的直接和间接影响及其机制,就紫外B辐射增强对昆虫影响方面迫切需要阐明的一些问题进行了讨论。     

Photoinhibition by solar radiation in the Mediterranean alga Peyssonnelia squamata measured on site

Photoinhibition of photosynthesis, defined as reversible decrease in the effective photosynthetic quantum yield, was measured in the Mediterranean red alga, Peyssonnelia squamata, using pulse amplitude modulation (PAM) chlorophyll fluorescence and oxygen production on site. This alga is adapted to very low fluence rates of solar radiation and is easily inhibited by exposure to excessive radiation. At high solar angles its photosynthetic capacity is impaired even in its natural habitat, in the protective shade of overhanging rocks. Oxygen production was maximal at 5 m depth and decreased to almost zero at the surface. When exposed at the surface oxygen production ceased within 16 min. The optimal photosynthetic quantum yield, defined as Fv/Fm, was about 0.45 in dark-adapted specimens. After 30 min of exposure to unattenuated solar radiation the (effective, Fv/Fm) quantum yield decreased to below 0.1. Removing solar UV (especially UV-B) significantly reduced photoinhibition: the quantum yield of a sample exposed under a UV-B cut-off filter was double that of a sample exposed to full solar radiation after 30 min exposure. Recovery from photoinhibition took several hours and was not complete after prolonged exposure (1.5 h) to direct solar radiation. The degree of photoinhibition depended on the depth at which the thalli were exposed. Recovery from photoinhibition was complete within 2 h except when the algae were exposed at the surface. When measured over the whole day, the effective photosynthetic quantum yield significantly decreased by about 25% from initially high values toward early afternoon and rose again towards evening. The data indicate that this alga is adapted to very low irradiances and is easily inhibited by excessive solar radiation; solar UV contributes substantially to the observed photoinhibition.     

Effects of solar and artificial radiation on motility and pigmentation in Cyanophora paradoxa

The effects of solar radiation and artificial UV irradiation on motility and pigmentation were studied in the flagellate system Cyanophora paradoxa. Both percentage of motile cells and average velocity decreased drastically after a solar exposure of a few hours. This effect was not due to an overheating since the cells were exposed under temperaturecontrolled conditions. Partial reduction of the UV-B radiation by cut-off filters or by insertion of an artificial ozone layer increased the tolerated exposure times. Artificial UV radiation also induced the same effects. Under both solar and artificial UV irradiation the photosynthetic pigments within the cyanelles were bleached also within short exposure times. Kinetics of pigment destruction showed that the accessory phycobilins are lost with a half life of 1.3 h while the chlorophylls had a half life of 33 h and a carotenoid with an absorption maximum at 480 nm of 17.3 h.     

Inhibition of photosynthesis by solar radiation in Dunaliella salina: relative efficiencies of UV-B, UV-A and PAR

Inhibition of photosynthesis after exposure to solar radiation was investigated in the marine green alga Dunaliella salina by monitoring photosynthetic optimal quantum yield F_v/F_m and efficiency of oxygen production. Samples were exposed to solar radiation in Ancient Korinth, Greece (37°58′ N, 23°0′ E) in August 1994. Within 30 min, F_v/F_m and efficiency of oxygen production decreased with similar kinetics with increasing exposure time. The inhibition, however, diminished when ultraviolet radiation was progressively excluded by means of colour filter glasses. Samples exposed for 3 h showed complete or partial recovery of photosynthesis, with almost the same rate under all irradition conditions. The fit of the experimental data with an analytical model describing inhibition of photosynthesis as a function of a linear combination of the photon fluence in the UV-B, UV-A and PAR allows one to estimate the relative mean effectiveness for inhibition by the three spectral ranges [about 2 × 10^?4, 4 × 10^?6 and 2 × 10^?7 (μmol photons m^?2)^?1 for UV-B, UV-A and PAR, respectively].