Impact of solar ultraviolet‐B radiation (290‐320 nm) upon marine microalgae

Abstract

For years scientists and laymen alike have casually noted the impact of solar ultraviolet radiation upon the non‐human component of the biosphere. It was not until recently, when human activities were thought to threaten the protective stratospheric ozone shield, that researchers undertook intensive studies into the biological stress caused by the previously neglected short‐wavelength edge of the global solar spectrum. Stratospheric ozone functions effectively as an ultraviolet screen by filtering out solar radiation in the 220–320 nm waveband as it penetrates through the atmosphere, thus allowing only small amounts of the longer wavelengths of radiation in this waveband to leak through to the surface of the earth. Although this ultraviolet radiation (UV‐B radiation, 290–320 nm) comprises only a small fraction (less than 1%) of the total solar spectrum, it can have a major impact on biological systems due to its actinic nature. Many organic molecules, most notably DNA and proteins, absorb UV‐B radiation which can initiate photochemical reactions. It is life's ability, or lack thereof, to cope with enhanced levels of solar UV‐B radiation that has generated the concern over the potential depletion of stratospheric ozone. The defense mechanisms that serve to protect both plants and animals from current levels of UV‐B radiation are quite varied. Whether these mechanisms will suffice for marine microalgae under conditions of enhanced levels of UV‐B radiation is the subject of this review.