Measured Trends in Stratospheric Ozone

Effects of ultraviolet radiation to Solea senegalensis during early development

Ultraviolet radiation (UVR) reaching the Earth surface is increasing and scarce information is available regarding effects of this stressor to early life stages of marine vertebrates. Therefore, this work aims to study the effects of UVR exposure during early development stages of the flatfish Solea senegalensis. Firstly, fish were exposed to UVR (six daily doses between 3.4 ± 0.08 and 8.6 ± 0.14 kJ m^-2) at the following moments: gastrula stage (24 h post fertilization, hpf), 1 and 2 days after hatching (dah, 48 and 72 hpf, respectively). In a second bioassay, fish at the beginning of metamorphosis were exposed to UVR (one or two daily doses of 7.2 ± 0.39 or 11.1 ± 0.49 kJ m^-2) and then maintained until the end of metamorphosis. Mortality and effects on development, growth and behaviour were evaluated at the end of both bioassays (3 dah and 18 dah, respectively). Biomarkers of neurotransmission (acetylcholinesterase, AChE), oxidative stress (catalase, CAT) and biotransformation (glutathione S-transferase, GST) were also determined at the end of the early larvae bioassay, and metamorphosis progression was evaluated during the second bioassay. UVR exposure caused distinct effects depending on life stage. Altered pigmentation, decreased growth, impaired fish behaviour and AChE and GST inhibition were observed at the earlier larval phase. Whereas, decrease in growth was the main effect observed at the metamorphosis stage. In summary, the exposure of S. senegalensis early stages to environmentally relevant UVR doses led to adverse responses at different levels of biological organization, which might lead to implications in later life stages.

Copper/Zinc Superoxide Dismutase in Human Skin: Current Knowledge

Superoxide dismutase is widespread in the human body, including skin and its appendages. Here, we focus on human skin copper/zinc superoxide dismutase, the enzyme that protects skin and its appendages against reactive oxygen species. Human skin copper/zinc superoxide dismutase resides in the cytoplasm of keratinocytes, where up to 90% of cellular reactive oxygen species is produced. Factors other than cell type, such as gender, age and diseased state influence its location in skin tissues. We review current knowledge of skin copper/zinc superoxide dismutase including recent studies in an attempt to contribute to solving the question of its remaining unexplained functions. The research described here may be applicable to pathologies associated with oxidative stress. However, recent studies on copper/zinc superoxide dismutase in yeast reveal that its predominant function may be in signaling pathways rather than in scavenging superoxide ions. If confirmed in the skin, novel approaches might be developed to unravel the enzyme's remaining mysteries.

Theoretical study of the oxidation reactions of sulfurous acid/sulfite with ozone to produce sulfuric acid/sulfate with atmospheric implications

Herein, theoretical studies were performed on the atmospheric oxidation of sulfurous acid (H₂SO₃) and sulfite ions (HSO₃⁻) by ozone (O₃) to produce sulfuric acid and hydrosulfate ions. The most favorable path for the H₂SO₃ + O₃ reaction has been found to be initiated from concerted H-abstraction and oxygen addition, with an overall energy barrier of 18.3 kcal mol⁻¹. On the other hand, the most favorable path for the HSO₃⁻ + O₃ reaction is initiated from oxygen addition, with an overall energy barrier of only 0.3 kcal mol⁻¹. Kinetic simulations were performed to estimate the significance of these reactions in the formation of atmospheric sulfate and destruction of the ozone layer. The results provide new insight into the missing source of atmospheric sulfate and particulate matter.

Herein, theoretical studies were performed on the atmospheric oxidation of sulfurous acid (H₂SO₃) and sulfite ions (HSO₃⁻) by ozone (O₃) to produce sulfuric acid and hydrosulfate ions.

Active Adoption of Void Formation in Metal-Oxide for All Transparent Super-Performing Photodetectors

Could ‘defect-considered’ void formation in metal-oxide be actively used? Is it possible to realize stable void formation in a metal-oxide layer, beyond unexpected observations, for functional utilization? Herein we demonstrate the effective tailoring of void formation of NiO for ultra-sensitive UV photodetection. NiO was formed onto pre-sputtered ZnO for a large size and spontaneously formed abrupt p-NiO/n-ZnO heterojunction device. To form voids at an interface, rapid thermal process was performed, resulting in highly visible light transparency (85–95%). This heterojunction provides extremely low saturation current (<0.1 nA) with an extraordinary rectifying ratio value of over 3000 and works well without any additional metal electrodes. Under UV illumination, we can observe the fast photoresponse time (10 ms) along with the highest possible responsivity (1.8 A W⁻¹) and excellent detectivity (2 × 10¹³ Jones) due to the existence of an intrinsic-void layer at the interface. We consider this as the first report on metal-oxide-based void formation (Kirkendall effect) for effective photoelectric device applications. We propose that the active adoption of ‘defect-considered’ Kirkendall-voids will open up a new era for metal-oxide based photoelectric devices.

Benthic N2 fixation in coral reefs and the potential effects of human-induced environmental change

Tropical coral reefs are among the most productive and diverse ecosystems, despite being surrounded by ocean waters where nutrients are in short supply. Benthic dinitrogen (N2) fixation is a significant internal source of "new" nitrogen (N) in reef ecosystems, but related information appears to be sparse. Here, we review the current state (and gaps) of knowledge on N2 fixation associated with coral reef organisms and their ecosystems. By summarizing the existing literature, we show that benthic N2 fixation is an omnipresent process in tropical reef environments. Highest N2 fixation rates are detected in reef-associated cyanobacterial mats and sea grass meadows, clearly showing the significance of these functional groups, if present, to the input of new N in reef ecosystems. Nonetheless, key benthic organisms such as hard corals also importantly contribute to benthic N2 fixation in the reef. Given the usually high coral coverage of healthy reef systems, these results indicate that benthic symbiotic associations may be more important than previously thought. In fact, mutualisms between carbon (C) and N2 fixers have likely evolved that may enable reef communities to mitigate N limitation. We then explore the potential effects of the increasing human interferences on the process of benthic reef N2 fixation via changes in diazotrophic populations, enzymatic activities, or availability of benthic substrates favorable to these microorganisms. Current knowledge indicates positive effects of ocean acidification, warming, and deoxygenation and negative effects of increased ultraviolet radiation on the amount of N fixed in coral reefs. Eutrophication may either boost or suppress N2 fixation, depending on the nutrient becoming limiting. As N2 fixation appears to play a fundamental role in nutrient-limited reef ecosystems, these assumptions need to be expanded and confirmed by future research efforts addressing the knowledge gaps identified in this review.

Effects of calcium cyanamide on soil microbial communities and Fusarium oxysporum f. sp. cucumberinum

Calcium cyanamide (CaCN(2)) has been one of the potential candidates as soil disinfectant since the restriction of methyl bromide in soil fumigation due to its ecological risk. However, little information is available on effects of CaCN(2) on soil microbial community. In this study, the soil microbial communities and the fate of pathogen Fusarium oxysporum (Schlechtend, Fr) f. sp. cucumberinum (Owen) Snyder and Hansen (F.O. f. sp. cucumberinum) in response to CaCN(2) treatment was evaluated. F.O. f. sp. cucumberinum population in soil treated with CaCN(2) at rates of 80 and 200 gm(-2) was suppressed by 88.7 and 92.2% after 15 d of CaCN(2) application. Bacterial, fungal, and actinomycete populations were also greatly decreased after 3 d of CaCN(2) application, but they recovered to the control level by 15 d. The variation in functional diversity of soil microbes characterized by principal component analysis, diversity and evenness indices based on Biolog data followed a similar trend. Meanwhile, the band number from the DGGE of soil 16S rDNA fragments increased from 9 for the non-CaCN(2)-treated soil to 10 or 12 after different rates of CaCN(2) application at 15 d, indicating the increase of abundant rDNA types in the community. The results suggest that CaCN(2) application had only a short-term and transitory impact on the indigenous soil microbial community in contrast to the long-term suppression of the F.O. f. sp. cucumberinum population. It is feasible to reduce Fusarium wilt without significant impact on microbial community by application of CaCN(2) at reasonable doses.

Acute effects of ultraviolet-A radiation on African catfish Clarias gariepinus (Burchell, 1822)

In the present work, the destructive effects of Ultraviolet-A radiation on the African Catfish, Clarias gariepinus was revealed in terms of total protein, cholesterol, glucose, hemoglobin and erythrocytic indices, differential blood cell counting, heamatocrite, creatinine level, Aspartic Amino Transferase, Alanine Amino Transferase and Alkaline Phosphatase. These destructive effects were also confirmed by histopathological changes in liver, blood corpuscles and skin.

Effects of UV-B radiation on seed yield of Glycine max and an assessment of F1 generation progeny for carryover effects

Glycine max (L.) Merr plants were grown outdoors in potted sand exposed to elevated ultraviolet-B (UV-B) radiation provided by filtered fluorescent lamps to determine the effects of UV-B on seed yield and UV-B-induced carryover effects in the F1 generation. Increased UV-B radiation had no detectable effects on reproductive parameters except for a reduction on seed number per plant and an increase in the number of unseeded pods per plant and dry weight of unseeded pods per plant in the field supplemental UV-B experiment. Studies on carryover effects in the greenhouse progeny growth trial also showed no effect of parental treatment with UV-B on biomass production, and most symbiotic-N traits and plant metabolite measured. However, the concentrations of N in nodules and starch in roots were significantly increased in the F1 generation progeny from elevated UV-B radiation relative to their F1 counterparts from ambient radiation. Assessing the effects of seed size on plant growth and symbiotic function in the F1 progeny showed that total biomass, dry matter yield of individual organs (leaves, stems, roots and nodules), total plant N and fixed-N rose with increasing seed size. Seed concentration of flavonoids was also enhanced with increasing seed size. These findings suggest that subtle changes did occur in the F1 generation progeny of parental plants exposed to elevated UV-B with potential to accumulate with further exposure to elevated UV-B radiation.

Photoinduced toxicity of selected PAHs to the marine microalga Phaeodactylum tricornutum

In this study, the effects of different concentrations of pyrene, phenanthrene, fluoranthene, and chrysene within the solubility limits of the chemicals on marine microalgal species of Phaeodactylum tricornutum were examined under UV-A and UV-B lights by application of batch toxicity tests. The algal species were also exposed to the individual PAHs under cool-white fluorescent bulbs in the same laboratory conditions in order to compare the results with the responses of UV-exposed organisms. EC50 values calculated with the trimmed Spearman Karber method demonstrate that the UV light dramatically enhances the toxicity of the selected model PAHs. In most cases, the magnitude of increase in PAH toxicity was directly related to the concentration of individual PAHs and the duration of UV-lighting.

DNA damage and developmental defects after exposure to UV and heavy metals in sea urchin cells and embryos compared to other invertebrates

The depletion of the stratospheric ozone layer and the resulting increase in hazardous ultraviolet-B (UV-B) radiation reaching the Earth are of major concern not only for terrestrial but also for aquatic organisms. UV-B is able to penetrate clear water to ecologically significant depths. This chapter deals with the effects of UV radiation on DNA integrity in marine benthic organisms, in particular sea urchins in comparison to other marine invertebrates (sponges and corals). These animals cannot escape the damaging effects of UV-B radiation and may be additionally exposed to pollution from natural or anthropogenic sources. Besides eggs and larvae that lack a protective epidermal layer and are particularly prone to the damaging effects of UV radiation, coelomocytes from the sea urchin Paracentrotus lividus were used as a "cellular sensor" to analyse the effects on DNA caused by UV-B, heavy metals (cadmium), and their combined actions. From our data we conclude that sea urchin coelomocytes as well as cells from other marine invertebrates are useful bioindicators of UV-B and heavy metal stress, responding to these stressors with different extents of DNA damage.

Effects of the interaction between genetic diversity and UV-B radiation on wood frog fitness

Genetic diversity may buffer amphibian populations against environmental vicissitudes. We hypothesized that wood frogs (Rana sylvatica)from populations with lower genetic diversity are more susceptible to ultraviolet-B (UV-B) radiation than those from populations with higher diversity. We used RAPD markers to obtain genetic diversity estimates for 12 wood frog populations. We reared larval wood frogs from these populations and exposed experimental groups of eggs and larvae to one of three treatments: unfiltered sunlight, sunlight filtered through a UM-B-blocking filter (Mylar), and sunlight filtered through a UV-B-transmitting filter (acetate). In groups exposed to UVB, larval mortality and deformity rates increased significantly, but egg mortality did not. We found a significant negative relationship between genetic diversity and egg mortality, larval mortality, and deformity rates. Furthermore, the interaction between UV-B treatment and genetic diversity significantly affected larval mortality. Populations with low genetic diversity experienced higher larval mortality rates when exposed to UVB than did populations with high genetic diversity. This is the first time an interaction between genetic diversity and an environmental stressor has been documented in amphibians. Differences in genetic diversity among populations, coupled with environmental stressors, may help explain patterns of amphibian decline.

Effects of nitrogen source and UV radiation on the growth, chlorophyll fluorescence and fatty acid composition of Phaeodactylum tricornutum and Chaetoceros muelleri (Bacillariophyceae)

Cultures of the marine diatoms Phaeodactylum tricornutum and Chaetoceros muelleri were grown in f/2 medium supplied with either nitrate (N-Nt), ammonium (N-Am) or urea (N-Ur) as the nitrogen (N) source at the same final N concentration (0.88 mM). Exponential growth phase cultures of the two diatoms were exposed to four different light regimes for 2 days: (UVAR) PAR (60 micromol quanta m-2 s-1) plus 8.22 W m-2 (unweighted) UVAR; (high UVBR) PAR (60 micromol quanta m-2 s-1) plus 1.04 W m-2 (unweighted) UVBR plus 13.73 W m-2 (unweighted) UVAR; (low UVBR) PAR (60 micromol quanta m-2 s-1) plus 0.19 W m-2 (unweighted) UVBR plus 2.76 W m-2 (unweighted) UVAR and (PAR) PAR (60 micromol quanta m-2 s-1) alone (control). No significant effects of N source on the growth rates of the two diatoms were detected. The maximum effective quantum yield of PSII, PhiPSIIe-max, and the initial slope of the light curve, alpha, of P. tricornutum and C. muelleri were all inhibited, whereas Ik was somewhat increased, as a consequence of 2 days of exposure to all the UVR treatments. Multiple factor ANOVA revealed that all the major fatty acids, both in P. tricornutum and C. muelleri, were influenced more strongly by N source than by UVR. The composition of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) in P. tricornutum and C. muelleri exhibited almost the same pattern of variation with N source and UVR. The maximum value of SFA was found in the N-Am treatment, that of MUFA in the N-Nt treatment and for PUFA in the N-Ur treatment irrespective of the UV radiation. On the other hand, the impact of UVR resulted in an increase of PUFA and a reduction of SFA both in P. tricornutum and C. muelleri under all N sources.

Coral bleaching: a potential biomarker of environmental stress

Coral bleaching refers to the loss of symbiotic algae by host corals, or to the loss of pigmentation by the algae themselves, causing corals to appear white or "bleached." Some corals may regain algae or pigmentation and survive, but when bleaching is severe the host coral dies. Coral bleaching events have increased dramatically in the last two decades, and coral reefs throughout the world have been extensively degraded as a result. This article reviews coral bleaching for investigators working in the field of toxicology and environmental health, a group of scientists not normally exposed to this issue. Several environmental stressors have been correlated with bleaching, including fluctuations in sea surface temperatures and salinity, increased sedimentation, increased solar radiation, and contaminants such as oil and herbicides. Molecular mechanisms of bleaching are only beginning to be investigated and are thus far poorly understood. Toxicologists have the potential to make significant contributions toward understanding anthropogenic aspects of coral bleaching and elucidating molecular mechanisms of this important environmental problem.

A field methodology to study effects of UV radiation on fish larvae

There is a considerable lack of in situ specific information about the effects of UV-B radiation on limnic animals studied in the field. We exposed larval pike (Esox lucius L.) in two types of cuvettes (glass and quartz) placed at different depths (5 or 15 cm) to natural solar UV or to artificially enhanced UV-B (lamps on 3 h per day), simulating the scenarios for coming decades. Dose realism and comparability with earlier laboratory experiments was the main purpose, and therefore UV-B irradiances to the surface as well as underwater irradiances were directly measured. Result showed that UV-B dose rates in natural waters are low even though DOC concentration was low (4.8 mg/l) in our study lake. A slight increase in ambient UV-B dose rates was enough to cause neurobehavioral symptoms in pike larvae. However, the dose rates applied were inadequate to affect superoxide dismutase (SOD) or HSP70. While assessing the suggested risks due to increased UV, conclusions emphasize the importance of conducting field UV studies as supplements to laboratory experiments. We also recommend direct measurements of UV-radiation at sites where the target organisms are actually exposed.