Ozone depletion and UVB radiation: Impact on plant DNA damage in southern South America

Abstract

The primary motivation behind the considerable effort in studying stratospheric ozone depletion is the potential for biological consequences of increased solar UVB (280 -315 nm) radiation. Yet, direct links between ozone depletion and biological impacts have been established only for organisms of Antarctic waters under the influence of the ozone ''hole;'' no direct evidence exists that ozone-related variations in UVB affect ecosystems of temperate latitudes. Indeed, calculations based on laboratory studies with plants suggest that the biological impact of ozone depletion (measured by the formation of cyclobutane pyrimidine dimers in DNA) is likely to be less marked than previously thought, because UVA quanta (315-400 nm) may also cause significant damage, and UVA is unaffected by ozone depletion. Herein, we show that the temperate ecosystems of southern South America have been subjected to increasingly high levels of ozone depletion during the last decade. We found that in the spring of 1997, despite frequent cloud cover, the passages of the ozone hole over Tierra del Fuego (55°S) caused concomitant increases in solar UV and that the enhanced ground-level UV led to significant increases in DNA damage in the native plant Gunnera magellanica. The fluctuations in solar UV explained a large proportion of the variation in DNA damage (up to 68%), particularly when the solar UV was weighted for biological effectiveness according to action spectra that assume a sharp decline in quantum efficiency with increasing wavelength from the UVB into the UVA regions of the spectrum.cyclobutane pyrimidine dimer ͉ global change ͉ Gunnera ͉ Tierra del Fuego T he most important consequence of the depletion of stratospheric ozone is the increased transmission of solar UVB radiation to the Earth's surface. Present levels of stratospheric ozone are at the lowest point since measurements began in the 1970s (1). Ozone depletion is most pronounced over the Antarctic continent, where ozone levels commonly decline by more than 70% during late winter and early spring [data available in the NASA Total Ozone Mapping Spectrometer (TOMS) site: http:͞͞jwocky.gsfc.nasa.gov͞TOMSmain.html]. Acute effects of ozone depletion on native organisms have been documented only for marine ecosystems of Antarctic waters (for a review, see ref.2). For example, it has been shown that increased UVB can reduce phytoplankton photosynthesis in the marginal ice zone when the ozone hole is overhead (3), reduce phytoplankton cell densities (4), and increase the DNA damage burden in icefish eggs (5). Virtually nothing is known about the consequences of ozone depletion and increased solar UVB on natural ecosystems located outside Antarctica.We have set up a long-term experiment to study the responses of terrestrial ecosystems to elevated solar UVB resulting from stratospheric ozone reduction near Ushuaia, Tierra del Fuego, Argentina. The area, dominated by temperate forests, is on the southern tip of South America, across the Drake Passage from the Antarctic Peninsula, an...

Effect of Solar Ultraviolet-B Radiation during Springtime Ozone Depletion on Photosynthesis and Biomass Production of Antarctic Vascular Plants

“…Ballarè et al (1996) found that transmission of greater percentages of ambient UV-B led to corresponding increases in leaf DNA damage levels in a summer annual. In one of the few studies to examine the relationship between natural temporal fluctuations in UV-B levels and plant response Rousseaux et al (1999) found that fluctuations in ambient UV-B BE dose explained a large proportion (68%) of the variation in leaf DNA damage levels over 14 sampling dates during springtime in southern Argentina. We found no significant correlations between any of the photosynthetic variables we measured and several UV-B parameters we examined, including midday UV-B BE , midday UV-B BE -to-PAR, and daily UV-B BE dose.…”

Health effects from stratospheric ozone depletion and interactions with climate change

“…For DNA damage, various action spectra were tested in the field in southern Argentina as the Antarctic "ozone hole" passed over the experimental site and altered the wavelength composition of the solar radiation. The comparisons of plant DNA damage responses with different action spectra indicated an action spectrum with little participation of UV-A as the most appropriate 12 Similarly, Mazza et al…”

Genome-wide analysis of gene expression reveals function of the bZIP transcription factor HY5 in the UV-B response of Arabidopsis

“…6). Increases in UV-B radiation due to depletion of the stratospheric ozone layer can be damaging to many living organisms (7)(8)(9)(10): for instance, UV-B is the most prominent physical carcinogen in the environment leading to the development of skin cancer in humans (11). High levels of UV-B radiation have a rather complex impact on cellular metabolism (including DNA and protein damage and lipid peroxidation), mainly by activating general stress responses (1,8,12).…”