Solar radiation is essential for life on Earth. The visible wavelength range, or photosynthetically active radiation (400 to 700 nm), provides the energy necessary for photosynthesis, which maintains oxygen in the atmosphere at levels sufficient for respiration and initiates carbon cycling in the earth biosphere. All wavelengths of solar radiation add heat to the Earth and its atmosphere and maintain temperatures within the ranges required by its biota. The shorter, ultraviolet wavelength ranges of solar radiation interact with molecular oxygen, primarily in the stratosphere, to produce ozone, which in turn protects biological systems in the troposphere from the very toxic UV-B wavelengths (see Chapter 2).

Solar radiation is also very toxic to biological processes. As is discussed thoroughly in these texts UVR can disrupt normal DNA replication and translation processes (e.g., [1-3], Chapter 9,10), alter the structure and function of other biomacromolecules (e.g., [4-7]), inhibit photosynthesis (e.g., [8-10], Chapter 11), produce alterations in epidermal and other tissues (e.g., [11,12], Chapter 13). And, at the population level, UVR can alter plankton assemblages (e.g., [1315]), and potentially affect the distribution and survival of other aquatic taxa [13]. Although exacerbated by recent anthropogenic impacts on stratospheric ozone, these processes are natural. Over millions of years of evolution species have developed mechanisms to avoid their damaging effects, at least at natural intensity and dose levels [1,9,13].


Br Br

C00H H

erythrosin B

1 -phenyl-1,3.5- heptatriyne polycyclic aromatic hydrocarbons

Q-Xj fluroanthene pyrene xx;.


- n acridine

benzo[a]pyrene natural plant compounds

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