Differential impacts of solar UV radiation on photosynthetic carbon fixation from the coastal to offshore surface waters in the South China Sea

We carried out experiments during an expedition (14 August to 14 September, 2007) that covered up to 250,000 km(2) to investigate the effects of solar UV radiation (UVR, 280-400 nm) on the photosynthetic carbon fixation of tropical phytoplankton assemblages in surface seawater of the South China Sea. From coastal to pelagic surface seawaters, UV-B (280-315 nm) caused similar inhibition, while UV-A (315-400 nm) induced photosynthetic inhibition increased from coastal to offshore waters. UV-B resulted in an inhibition by up to 27% and UV-A by up to 29%. Under reduced levels of solar radiation with heavy overcast, UV-A resulted in enhanced photosynthetic carbon fixation by up to 25% in coastal waters where microplankton was abundant. However, such a positive impact was not observed in the offshore waters where piconanoplankton was more abundant. The daily integrated inhibition of UV-A reached 4.3% and 13.2%, and that of UV-B reached 16.5% and 13.5%, in the coastal and offshore waters, respectively.     

Effect of Ultraviolet Radiation on Acetylcholinesterase Activity in Freshwater Copepods

We analyzed the effects of UV radiation (UVR) effects on acetylcholinesterase (AChE) activity in two calanoid copepods, Boeckella gibbosa and Parabroteas sarsi that inhabit Patagonian shallow lakes. We studied the effect of experimental UVR (UV-B and UV-A) exposure on AChE activity in relation to basal antioxidant capacities of both copepods. Our experiments showed that UVR can effectively depress AChE activity, although with differences between species. In both copepods AChE was affected by UV-B, whereas UV-A only affected AChE in B. gibbosa. Both copepods also differed in body elemental composition (C:N:P), photoprotecting compound content (carotenoids and mycosporine-like amino acids) and enzymatic antioxidant capacity (glutathione S-transferase [GST]). Our results suggest that when exposed to UVR, AChE activity would depend more on the antioxidant capacity (GST) and P availability for enzyme synthesis than on the photoprotective compounds.     

A Five‐year Study of Solar Ultraviolet Radiation in Southern Chile (39° S): Potential Impact on Physiology of Coastal Marine Algae?

This study reports 5 years of (1998-2003) data on continuous solar-irradiation measurements from a scanning spectroradiometer (SUV-100) in Valdivia, Chile (39 degrees S), accompanied by evaluation of the impact of ultraviolet radiation (UVR) on marine macroalgae of this site. UVR conditions showed a strong seasonal variation, which was less pronounced toward longer wavelengths. Daily maximum dose rates (clear days) averaged in winter-summer: UV-B(290-315 nm) 0.30-2.1, UV-B(290-320 nm) 0.70-3.7, UV-A(315-400 nm) 20.6-62.1, UV-A(320-400 nm) 20.2-60.5 W m(-2), and photosynthetically active radiation (PAR) 969-2423 micromol m(-2) s(-1). The corresponding daily doses (all the days) ranged: UV-B(290-315 nm) 2.6-40.7, UV-B(290-320 nm) 6.7-78.5, UV-A(315-400 nm) 228-1539, UV-A(320-400 nm) 224-1501, and PAR 2008-13308 kJ m(-2) d(-1). Taking into consideration action spectra of a biological interest, the risk of UV exposure could be up to 37 times higher in summer than in winter. The photosynthetic activity (as maximum quantum yield of chlorophyll fluorescence, F(v)/F(m)) of the brown alga Lessonia nigrescens from the infralittoral zone was markedly more sensitive to UVR than of the green alga Enteromorpha intestinalis from the upper midlittoral, and the UV-B wave band increased markedly photoinhibition. In L. nigrescens, maximal photoinhibition (40%) took place at weighted (the action spectrum for photoinhibition of photosynthesis) UVR doses of 800 kJ m(-2), irrespective of the season (corresponding midsummer daily dose in Valdivia is 480 kJ m(-2)). In winter, when this alga was at its most sensitive, the weighted UV dose causing 35-40% photoinhibition was around 200 kJ m(-2). In E. intestinalis, weighted doses of 800 kJ m(-2) resulted in low photoinhibition (<10 %) and no clear seasonal patterns could be inferred. These results confirm that midday summer levels of UV-B and their daily doses in southern Chile are high enough to produce stress to intertidal macroalgae.     

Monitoring of Solar Irradiance in the High Andes

Solar radiation has been measured in the high Andes near Laguna Lejia (latitude 23° 26′ 23.30" S, longitude 67° 38′ 14.29" W) at an elevation of 4715 m between December 2016 and December 2017. Irradiances were monitored in four wavelength channels: PAR (400–700 nm), UV-A (315–400 nm), UV-B (295–315 nm) and short-wavelength UV-B (295–310 nm) with a new radiometer. In addition, ambient temperatures were recorded. Record values have been found for PAR (exceeding 600 W m⁻²), UV-A (close to 95 W m⁻²), UV-B (3.13 W m⁻²) and short-wavelength UV-B (0.144 W m⁻²) during Austral spring. The winter irradiance values slightly exceeded 50% of these values. Maximal cloud effects due to multiple reflections were 45, 38, 32 and 35% higher than values under cloudless skies for PAR, UV-A, UV-B and short-wavelength UV-B, respectively. Record irradiance for this site shows a UV index reaching and exceeding 20, which is due to low solar zenith angles, the altitude, low water vapor and aerosol concentrations in the atmosphere as well as low total column ozone concentrations.     

POTENTIAL ERRORS IN THE USE OF CELLULOSE DIACETATE AND MYLAR FILTERS IN UV-B RADIATION STUDIES

Abstract— The increase in UV-B radiation(290–320 nm) penetrating to the earth's surface as a result of the chemical depletion of the stratospheric ozone layer is an important environmental concern. In most studies using artificial UV-B sources, the determination of enhanced UV-B radiation effects on plants relies on equivalent UV-A radiation(320–400 nm) from the experimental UV-B fluorescent lamp source, filtered with either cellulose diacetate (CA) to create UV-B treatments, or with type S Mylar or polyester (PE) to create controls (no UV-B). The spectral irradiance in the UV-A was measured in the dark below lamps at two daily UV-B irradiance levels (14.1 and 10.7 W m^-2) with CA and PE at two ages. Highly significant differences in UV-A radiation (P 0.01) were measured below the treatment/control pairs at both fluence rates and filter ages. Filter aging was observed, which reduced the UV-A irradiance, especially for PE. The total daily ambient UV-A irradiance was also determined in the glasshouse at three seasons: the fall equinox, summer and winter, from which the total daily UV-A (lamp + ambient) irradiances were calculated. The addition of low to moderate ambient irradiance removed the treatment/control differences in the longwave UV-A(350–400 nm); however, the treatment/contro1 differences remained in the shortwave UV-A(320–350 nm), which was restricted by the glass, and in the total UV-A. The treatment/control differences persisted in the shortwave UV-A for the higher irradiance level, even under high summer ambient light. Also, spectral ratios (UVB:UV-A and shortwave: longwave UV-A) for all treatment groups decreased as the ambient UV-A radiation increased. Therefore, a range of experimental conditions exist where PE-covered lamps do not provide adequate control for UV-A irradiance, relative to the CA treatment, for glasshouse/growth chamber experiments. Potential complications in the interpretation of plant response exist for UV-B experiments conducted under low ambient light conditions (e.g. growth chambers; glasshouse in winter) or high daily UV-B irradiances (e.g. 14 kJ m^-2) for those plant responses that are sensitive to UV-A radiation.     

Responses of a marine red tide alga Skeletonema costatum (Bacillariophyceae) to long-term UV radiation exposures

UV radiation (280–400 nm) is known to affect phytoplankton in negative, neutral and positive ways depending on the species or levels of irradiation energy. However, little has been documented on how photosynthetic physiology and growth of red tide alga respond to UVR in a long-term period. We exposed the cells of the marine red tide diatom Skeletonema costatum for 6 days to simulated solar radiations with UV-A (320–400 nm) or UV-A + UV-B (295–400 nm) and examined their changes in photosynthesis and growth. Presence of UV-B continuously reduced the effective photosynthetic quantum yield of PSII, and resulted in complete growth inhibition and death of cells. When UV-B or UV-B + UV-A was screened off, the growth rate decreased initially but regained thereafter. UV-absorbing compounds and carotenoids increased in response to the exposures with UVR. However, mechanisms for photoprotection associated with the increased carotenoids or UV-absorbing compounds were not adequate under the continuous exposure to a constant level of UV-B (0.09 W m^?2, DNA-weighted). In contrast, under solar radiation screened off UV-B, the photoprotection was first accomplished by an initial increase of carotenoids and a later increase in UV-absorbing compounds. The overall response of this red tide alga to prolonged UV exposures indicates that S. costatum is a UV-B-sensitive species and increased UV-B irradiance would influence the formation of its blooms.     

Resistance of a Lizard (the Green Anole, Anolis carolinensis; Polychridae) to Ultraviolet Radiation–induced Immunosuppression¶

The green anole (Anolis carolinensis) is the most northerly distributed of its Neotropical genus. This lizard avoids a winter hibernation phase by the use of sun basking behaviors. Inevitably, this species is exposed to high doses of ambient solar ultraviolet radiation (UVR). Increases in terrestrial ultraviolet-B (UV-B) radiation secondary to stratospheric ozone depletion and habitat perturbation potentially place this species at risk of UVR-induced immunosuppression. Daily exposure to subinflammatory UVR (8 kJ/m2/day UV-B, 85 kJ/m2/day ultraviolet A [UV-A]), 6 days per week for 4 weeks (total cumulative doses of 192 kJ/m2 UV-B, 2.04 x 10(3) kJ/m2 UV-A) did not suppress the anole's acute or delayed type hypersensitivity (DTH) response to horseshoe crab hemocyanin. In comparison with the available literature UV-B doses as low as 0.1 and 15.9 kJ/m2 induced suppression of DTH responses in mice and humans, respectively. Exposure of anoles to UVR did not result in the inhibition of ex vivo splenocyte phagocytosis of fluorescein labeled Escherichia coli or ex vivo splenocyte nitric oxide production. Doses of UV-B ranging from 0.35 to 45 kJ/m2 have been reported to suppress murine splenic/peritoneal macrophage phagocytosis and nitric oxide production. These preliminary studies demonstrate the resistance of green anoles to UVR-induced immunosuppression. Methanol extracts of anole skin contained two peaks in the ultraviolet wavelength range that could be indicative of photoprotective substances. However, the resistance of green anoles to UVR is probably not completely attributable to absorption by UVR photoprotective substances in the skin but more likely results from a combination of other factors including absorption by the cutis and absorption and reflectance by various components of the dermis.     

EFFECTS OF SOLAR RADIATION ON MOTILITY IN: Stentor coeruleus

The effects of solar radiation on the motility of the colored ciliate, Stentor coeruleus, have been assessed as a photodynamic model system for hypericism. The organism has been found to be extremely sensitive to solar radiation–a few minutes of unfiltered radiation suffice to arrest motility and decrease the velocity of movement. Removing UV-B and UV-A radiation prolongs the tolerated exposure times. From the present study, the mechanisms of the photodynamic action in S. coeruleus and in hypericin-sensitized reactions have not been resolved in terms of Type I and II mechanisms.     

Effects of UVR and UVR-induced cytokines on production of extracellular matrix proteins and proteases by dermal fibroblasts cultured in collagen gels%

Synthesis of extracellular matrix (ECM) proteins and their degradation by matrix metalloproteinases (MMP) are part of the dermal remodeling resulting from chronic exposure of skin to ultraviolet radiation (UVR). We have compared two alternative mechanisms for these responses, namely, a direct mechanism in which UV-B or UV-A is absorbed by fibroblasts and an indirect mechanism in which cytokines, produced in skin in response to UVR, stimulate production of the ECM proteins and MMP. These studies were carried out on human dermal fibroblasts grown in contracted, free-floating 9 day old collagen gels as a dermal equivalent. Synthesis of tropoelastin, collagen, fibrillin, MMP-1, -2, -3 and -9 and tissue inhibitors of metalloproteinases (TIMP)-1 and -2 were measured. Tropoelastin, collagen and fibrillin levels were stable between days 4 and 10, and MMP and TIMP decreased by day 10. Neither UV-B (2.5-50 mJ/cm2) nor UV-A (2-12 J/cm2) altered synthesis of ECM proteins, but UV-A increased MMP-1 and -3 production. Tropoelastin synthesis increased in response to transforming growth factor-beta1 (5 ng/mL) treatment. Both interleukin-1beta and tumor necrosis factor-alpha (10 ng/mL) decreased fibrillin messenger RNA levels but increased MMP-1, -3 and -9 synthesis markedly. Collagen synthesis was not modulated by UV-B, UV-A or cytokine treatment. These results indicate that certain cytokines may have greater effects on production of ECM proteins and MMP than absorption of UV-B and UV-A by fibroblasts grown in dermal equivalents and suggest that the former pathway may play a role in the dermal remodeling in photoaged skin.     

Solar UV Irradiances Modulate Effects of Ocean Acidification on the Coccolithophorid Emiliania huxleyi

Emiliania huxleyi, the most abundant coccolithophorid in the oceans, is naturally exposed to solar UV radiation (UVR, 280–400 nm) in addition to photosynthetically active radiation (PAR). We investigated the physiological responses of E. huxleyi to the present day and elevated CO₂ (390 vs 1000 μatm; with pH_NBS 8.20 vs 7.86) under indoor constant PAR and fluctuating solar radiation with or without UVR. Enrichment of CO₂ stimulated the production rate of particulate organic carbon (POC) under constant PAR, but led to unchanged POC production under incident fluctuating solar radiation. The production rates of particulate inorganic carbon (PIC) as well as PIC/POC ratios were reduced under the elevated CO₂, ocean acidification (OA) condition, regardless of PAR levels, and the presence of UVR. However, moderate levels of UVR increased PIC production rates and PIC/POC ratios. OA treatment interacted with UVR to influence the alga's physiological performance, leading to reduced specific growth rate in the presence of UVA (315–400 nm) and decreased quantum yield, along with enhanced nonphotochemical quenching, with addition of UVB (280–315 nm). The results clearly indicate that UV radiation needs to be invoked as a key stressor when considering the impacts of ocean acidification on E. huxleyi.     

AMELIORATION OF UV-B DAMAGE UNDER HIGH IRRADIANCE. II: ROLE OF BLUE LIGHT PHOTORECEPTORS

Abstract Sensitivity of plants to UV-B radiation (280–315 nm) is often reduced at high background irradiance. Interpretation of plant responses to potential increases in solar UV-B requires improved understanding of interactions between UV-B and other environmental parameters. In this study, photosynthetically active radiation (PAR, 400–700 nm) was kept approximately constant (38 mol m-² per day) while the daily blue light fluence (BL, 400–500 nm) was varied between 0.23 and 2.68 mol m-². Two lines of cucumber (cvs Ashley and Poinsett) with differential sensitivity to UV-B were compared. At low BL, 3 days of UV-B treatment (21 kJ m-² biologically effective radiation per 10 h per day) caused severe inhibition of growth in a developing leaf in both cultivars. Growth effects were detectable sooner and were accompanied by chlorotic lesions in the sensitive cultivar (cv Poinsett). Supplemental BL progressively reduced symptoms, consistent with an important role for BL photoreceptor(s) in prevention or repair of UV-B damage. Ultraviolet-induced increases in UV-absorbing compounds on an area basis were significant within 24 h of the start of the treatment but were independent of BL fluence over the range tested, suggesting that bulk accumulation of screening pigments did not contribute to BL-dependent amelioration of UV damage. However, BL did stimulate net increases in extractable UV-absorbing compounds on a total leaf busis, while high-performance liquid chromatography analysis indicated that BL and UV-B acted synergistically to increase specific components. Thus, the data do not necessarily exclude UV-absorbing compounds from an important role in overall UV-B protection nor do they rule out some more specific function for these compounds (e.g. antioxidants). Finally, BL effects on UV-B alteration of leaf growth and accumulation of UV-absorbing compounds were not saturated under the conditions used here, suggesting that BL may contribute to interactions between UV-B and natural levels of background irradiance. Caution is urged in the interpretation of data on UV-B effects obtained under conditions of low BL irradiance.     

A PERSONAL DOSIMETER FOR BIOLOGICALLY EFFECTIVE SOLAR UV-B RADIATION

Abstract— The production and optical properties are described of a polymer film suitable for use as a personal dosimeter for biologically effective solar UV-B radiation. The dosimeter only responds to UVR at wavelengths less than 315 nm and is potentially suited for longterm studies of the UV doses received by human subjects.     

Penetration of ultraviolet radiation in the marine environment. A review

UV radiation (UVR) is a significant ecological factor in the marine environment that can have important effects on planktonic organisms and dissolved organic matter (DOM). The penetration of UVR into the water column is likely to change in the near future due to interactions between global warming and ozone depletion. In this study we report underwater instruments employed for the measurement of UVR and we review data dealing with the depth of UVR penetration in different oceanic areas including the open ocean, Antarctic waters and coastal waters. We provide the 10% irradiance depth (Z10%) for UV-A and UV-B as well as for DNA damage effective dose (DNA), which we calculated from the values of diffuse attenuation coefficients or vertical profiles reported in the literature. We observe a clear distinction between open ocean (high Z10%, no variation in the ratio UV-B/UV-A), Antarctic waters (increase in the ratio UV-B/UV-A during ozone hole conditions) and coastal waters (low Z10%, no variation in the ratio UV-B/UV-A). These variations in the penetration of UVR could lead to differences in the relative importance of photobiological/photochemical processes. We also compare in this study the penetration of UV-B (unweighted and weighted by the Setlow action spectrum) and DNA damage effective dose.     

Variable fluorescence parameters in the filamentous Patagonian rhodophytes, Callithamnion gaudichaudii and Ceramium sp. under solar radiation

The filamentous rhodophytes Callithamnion gaudichaudi Agardh and Ceramium sp. were utilized to study the effects of solar radiation (PAR, 400-700 nm, UV-B, 280-315 nm and UV-A, 315-400 nm) on the photosynthetic performance in situ in Patagonia waters (Argentina). A pulse amplitude modulated (PAM) fluorometer was used to determine the fluorescence parameters. The two species grew in different habitats in the eulittoral: Ceramium sp. was found only in rock pools while C. gaudichaudii grew on exposed rocks and fell dry during low tide. Both species differed in their fluorescence parameters and their sensitivity to solar radiation exposure. The photosynthetic quantum yield had its lowest values at noon, but it recovered in the afternoon/evening hours, when irradiances were lower. PAR (irradiance of about 400 W m(-2) at noon) was responsible for most of the decrease in the yield on clear days, especially in Ceramium sp., but UVR (280-400 nm) also accounted for a significant decrease. Fluence rate response curves indicated that both species were adapted to low fluence rates and showed a pronounced non-photochemical quenching at intermediate and higher irradiances. Both species showed a rapid adaptation during measurement of fast induction kinetics but differed significantly in their fluorescence components. All photosynthetic pigments were bleached after 8 h exposure to solar radiation over a full day. Strong absorption in the UV-A range, most likely due to mycosporine-like amino acids, was detected in both strains. The pronounced sensitivity to solar radiation in situ and the recovery capacity of these two filamentous Rhodophyte species, as well as the presence of protective compounds, suggests that these algae have the ability to adapt to the relatively high radiation levels and changes in irradiance found in the Patagonia waters.     

ELDONET--a decade of monitoring solar radiation on five continents

The European light dosimeter network (ELDONET) comprises more than 40 stations in 24 countries on 5 continents. The present report compares solar radiation data in the photosynthetic active radiation, UV-A (315-400 nm) and UV-B (280-315 nm) wavelength ranges for 17 stations at different latitudes on the northern and southern hemispheres for up to 10 years of monitoring. While the maximal irradiances on clear days follow a latitudinal gradient due to the cosine dependence on the solar angle, the total doses strongly depend on the local climate and atmospheric conditions as well as the day-length distribution over the year. UV-B irradiances and doses are strongly influenced by the total column ozone, which is recorded for all covered stations.     

Impact of solar ultraviolet radiation on marine phytoplankton of Patagonia, Argentina

Patagonia area is located in close proximity to the Antarctic ozone "hole" and thus receives enhanced ultraviolet B (UV-B) radiation (280-315 nm) in addition to the normal levels of ultraviolet A (UV-A; 315-400 nm) and photosynthetically available radiation (PAR; 400-700 nm). In marine ecosystems of Patagonia, normal ultraviolet radiation (UVR) levels affect phytoplankton assemblages during the three phases of the annual succession: (1) prebloom season (late summer-fall), (2) bloom season (winter-early spring) and (3) postbloom season (late spring-summer). Small-size cells characterize the pre- and postbloom communities, which have a relatively high photosynthetic inhibition because of high UVR levels during those seasons. During the bloom, characterized by microplankton diatoms, photosynthetic inhibition is low because of the low UVR levels reaching the earth's surface during winter; this community, however, is more sensitive to UV-B when inhibition is normalized by irradiance (i.e. biological weighting functions). In situ studies have shown that UVR significantly affects not only photosynthesis but also the DNA molecule, but these negative effects are rapidly reduced in the water column because of the differential attenuation of solar radiation. UVR also affects photosynthesis versus irradiance (P vs E) parameters of some natural phytoplankton assemblages (i.e. during the pre- but not during the postbloom season). However, there is a significant temporal variability of P vs E parameters, which are influenced by the nutrient status of cells and taxonomic composition; taxonomic composition is in turn associated with the stratification conditions (e.g. wind speed and duration). In Patagonia, wind speed is one of the most important variables that conditions the development of the winter bloom by regulating the depth of the upper mixed layer (UML) and hence the mean irradiance received by cells. Studies on the interactive effects of UVR and mixing show that responses of phytoplankton vary according to the taxonomic composition and cell structure of assemblages; therefore cells use UVR if >90% of the euphotic zone is being mixed. In fact, cell size plays a very important role when estimating the impact of UVR on phytoplankton, with large cells being more sensitive when determining photosynthesis inhibition, whereas small cells are more sensitive to DNA damage. Finally, in long-term experiments, it was determined that UVR can shape the diatom community structure in some assemblages of coastal waters, but it is virtually unknown how these changes affect the trophodynamics of marine systems. Future studies should consider the combined effects of UVR on both phytoplankton and grazers to establish potential changes in biodiversity of the area.     

AMELIORATION OF UV-B DAMAGE UNDER HIGH IRRADIANCE. I: ROLE OF PHOTOSYNTHESIS

Sensitivity to ultraviolet-B radiation (UV-B,280–315 nm) is generally reduced when background irradiance is high. We tested the involvement of photosynthesis in the amelioration of UV-B damage by treating plants at high PAR (photosynthetically-active radiation, 400–700 nm; 1000 μmol m-² s-¹) with supplemental UV-B at double ambient levels of biologically-effective radiation (18 kJ m-²d-¹) and either “ambient” (450 μmol mol-¹) or short term elevated (750 μmol mol-¹) CO₂ levels. Responses to UV-B were assessed by photosynthetic gas exchange, leaf expansion and production of UV-absorbing compounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.) previously demonstrated to be relatively sensitive (cv. Poinsett) and insensitive (cv. Ashley) to UV-B. Except for marginal leaf interveinal chlorosis observed in Poinsett, both cultivars responded similarly. UV-B had little direct effect on leaf photosynthesis, but it did cause reductions in leaf area and corresponding increases in leaf dry matter per area. Increased CO, stimulated plant growth, counteracting the effect of UV-B on leaf growth and indicating an important role for photosynthesis. In contrast, the accumulation of UV-absorbing flavonoid compounds was enhanced by UV-B exposure but was not affected by COz enrichment.     

ULTRAVIOLET ERYTHEMA SENSITIVITY IN ANAMNESTIC (I-IV) and PHOTOTESTED (1–4) CAUCASIAN SKIN PHOTOTYPES: THE NEED FOR A NEW CLASSIFICATION SYSTEM

Abstract— The anamnestic skin phototypes (ASP) I-IV^1,2 of 21 Caucasian volunteers were compared with their phototested skin phototypes (PSP) using solar simulating, broadband UV radiation. The Commission Internationale de' éclairage (CIE)-weighted (i.e. erythemally effective) minimal erythema doses (MED) for solar simulating radiation varied from 20 mJ/cm² (PSP type 1) to 57 mJ/cm² (PSP type 4). In only 11 of 21 volunteers did the ASP (I-IV) and PSP (1–4) classifications coincide, and the MED values of the volunteers within the different ASP groups (I-IV) overlapped considerably. To compare the reactivity to erythematogenic radiation of different wavelengths, narrowband monochromator irradiations were performed at 298 nm, 310 nm and 330 nm. The CIE-weighted MED values at these wavelengths (20–80 mJ/cm²) corresponded well with those obtained in the broadband testing. Our results indicate that, with classification by interrogation, Caucasian skin can reliably be classified into only two subtypes, corresponding to Fitzpatrick phototypes I–III and phototype IV, respectively. A classification into four sensitivity types can be achieved by phototesting, only. We propose that the concept of ASP should be used with caution. The concept of PSP 1–4 should be favored.     

DISCREPANCIES IN THE MEASUREMENT OF SPECTRAL SOURCES

Abstract— Comparison of spectroradiometric and meter measurements of a series of ultraviolet radiation sources indicates that a wide divergence between readings can occur. We found that with a xenon are filtered as a solar simulator producing UV-A (320–400 nm) and UV-B (290–320 nm) radiation, the meter can either over-or underestimate the emission of the source when different cutoff filters are used. The most severe discrepancy appears with the UV-B meter reading, although the UV-A reading can also be problematic. Meters should be calibrated against the specific sources they will be used to measure.     

Use of UV-A Energy for Photosynthesis in the Red Macroalga Gracilaria lemaneiformis

UV radiation is known to inhibit photosynthetically active radiation (PAR)-driven photosynthesis; however, moderate levels of UV-A have been shown to enhance photosynthesis and growth rates of some algae. Here, we have shown that UV-A alone could drive photosynthetic utilization of bicarbonate in the red alga Gracilaria lemaneiformis as evidenced in either O₂ evolution or carbon fixation as well as pH drift. Addition of UV-B inhibited the apparent photosynthetic efficiency, raised the photosynthetic compensation point and photosynthesis-saturating irradiance level, but did not significantly affect the maximal rate of photosynthetic O₂ evolution. The electron transport inhibitor, DCMU, inhibited the photosynthesis completely, reflecting that energy of UV-A was transferred in the same way as that of PAR. Inorganic carbon acquisition for photosynthesis under UV alone was inhibited by the inhibitors of carbonic anhydrase. The results provided the evidence that G. lemaneiformis can use UV-A efficiently to drive photosynthesis based on the utilization of bicarbonate, which could contribute significantly to the enhanced photosynthesis in the presence of UV-A observed under reduced levels of solar radiation.