Sometimes Even Algae Gets Sunburned

The pale color and white tips of this red algae is the result of too much ultraviolet radiation. (Photo Credit: Max Schwanitz, Alfred Wegener Institute)

The pale color and white tips of this red algae is the result of too much ultraviolet radiation. (Photo Credit: Max Schwanitz, Alfred Wegener Institute)

Plants and photosynthetic algae rely on the Sun as a source of energy to power photosynthesis. Without the Sun, these organisms would not be able to make the energy needed to perform the functions necessary for survive. However, there is such a thing as too much Sun. Similar to the sunburn you may get after sitting in the Sun too long, plants are also susceptible to overdoses of ultraviolet radiation.

When plants receive more light than they can use, light sensitive pigments used to absorb light for photosynthesis may become damaged. Overexposure to light may result in black spots, pale leaves, or rotten parts on the affected plant. Many plants and photosynthetic algae have developed strategies to deal with an excess of ultraviolet radiation.

For example, when a certain species of red algae receives too much ultraviolet radiation, the algae produces fewer red light-collecting proteins so that less radiation is absorbed. Outwardly, the algae turns a paler shade of red and forms white tips. In addition, the algae also produces mycosporin amino acids, a substance similar to melanin in humans. In humans, melanin absorbs ultraviolet radiation, protecting the skin from harm and forming a natural suntan.

However, due to the depletion of the ozone layer, more dangerous short-wavelength ultraviolet radiation is able to penetrate the Earth’s surface and seawater. The mechanisms that plants and photosynthetic algae have to protect themselves from ultraviolet radiation do not work well against these more harmful ultraviolet rays. In algae, the more dangerous ultraviolet radiation harms the organism’s ability to photosynthesize and negatively impacts the organism’s DNA. This damage leads to a much slower rate of growth and reduced reproductive success for the algae. Particularly sensitive are spores and algal gametes, for which even tiny doses of ultraviolet radiation are deleterious.

Researchers associated with the German French Research Base AWIPEV on Spitsbergen (a Norwegian island in the Arctic) have found that the distribution of certain species of algae are inhibited by ultraviolet radiation. They also found that as ultraviolet radiation increases, the algae are displaced into even deeper waters. According to the researchers, continued study of underwater algae is important as it illustrates how marine coastal ecosystems are being impacted by global climate change.

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