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2 results

  • 16 - Ultraviolet Radiation Effects under Climate Change

  • from Part III - The Future
  • Edited by Mario Giordano, Università degli Studi di Ancona, Italy, John Beardall, Monash University, Victoria, John A. Raven, University of Dundee, Stephen C. Maberly, UK Centre for Ecology & Hydrology, Lancaster
  • Book:
    Evolutionary Physiology of Algae and Aquatic Plants
    Published online:
    24 October 2024
    Print publication:
    07 November 2024, pp 315-340

  • Summary

    Solar radiation at the Earth’s surface contains ultraviolet (UV) radiation in the UVB (~295–315 nm) and UVA (315–400 nm) wavebands. Currently, atmospheric ozone removes shorter, more damaging UV radiation and reduces levels of UVB, but before the formation of the ozone layer, UV radiation levels would have been higher, while the recent ‘ozone hole’ increased UV radiation. UV radiation is strongly attenuated in water, but aquatic organisms can be damaged to extents that depend on the species and conditions. The targets of damage include proteins in the photosystems of photosynthesis, DNA and oxidative damage caused by the production of free radicals and reactive oxygen species. Defence against damage involves the production of new proteins, repair to the DNA and the production of antioxidants. UV stress interacts, positively and negatively, with other environmental changes such as rising temperature and CO2, ocean acidification and nutrient stress. Further research is needed to forecast responses to future environmental change.

  • DNA damage and photosynthetic inhibition induced by solar ultraviolet radiation in tropical phytoplankton (Lake Titicaca, Bolivia)

  • E. WALTER HELBLING, VIRGINIA E. VILLAFAÑE, ANITA G. J. BUMA, MARCOS ANDRADE, FRANCESCO ZARATTI
  • Journal:
    European Journal of Phycology / Volume 36 / Issue 2 / May 2001
    Published online by Cambridge University Press:
    23 July 2001, pp. 157-166
    Print publication:
    May 2001

  • Experiments were conducted during October 1998 in Lake Titicaca, Bolivia (16° S, 68° W, 3810 m a.s.l), to determine the effects of solar ultraviolet radiation (UVR) on phytoplankton photosynthetic rates and DNA damage. Water samples were taken daily and incubated in situ or in simulated in situ conditions using sharp cut-off filters to eliminate various portions of the UVR spectrum. The total inhibition of photosynthesis due to UVR in surface waters was 85%; the greatest part of this inhibition (65%) was due to UVAR (315–400 nm), the rest (20%) being due to UVBR (280–315 nm). The inhibition of photosynthesis decreased with depth so that there were no significant differences among treatments at 1·3 optical depths (KPAR). The loss of carbon assimilation in the integrated production over the euphotic zone (4·6 optical depths) was 17·4%, with 14% due to UVAR and an additional 3·4% due to UVBR. Lake Titicaca phytoplankton had a threshold for inhibition of photosynthesis at about 0·3 W m−2 for UVBR and 5 W m−2 for UVAR, below which no inhibition was detected. Above this threshold, photosynthetic inhibition increased steadily, with UVAR having the greatest effect. Analysis of biological weighting functions (BWFs) indicated that phytoplankton from Lake Titicaca was less sensitive to UVR than phytoplankton from other regions. DNA damage (evaluated through the formation of cyclobutane pyrimidine dimers, CPDs) was observed for a simulated worst-case situation (i.e. samples incubated in full sunlight) and significant CPD accumulation was found as a result of UVBR exposure, but not with UVAR. However, absolute levels of damage were relatively low when compared with results obtained at other locations, also suggesting the low sensitivity of Lake Titicaca phytoplankton to UVR. It seems that UVBR stress in these organisms acts via at least two cellular targets: the photosynthetic apparatus and nuclear DNA. Our results suggest that an eventual enhancement of UVBR, due to ozone depletion, would have little impact on the phytoplankton of Lake Titicaca.