It is red, it burns and itches: a sunburn on our skin. However, too much sun is not only bad for humans. Many plants react very sensitive to an exposure to ultraviolet radiation, too. Yet they are dependent on sunlight. With the help of pigments absorbing solar energy and light, plants produce their cellular components by means of photosynthesis. However, this has its limits: too much sun means an over-abundance of energy and thus the destruction of the sensitive pigments. The results are black spots, pale leaves and rotten parts.
Since algae cannot apply sun lotion like we do, they develop their own strategies to protect against the harmful sunrays: “One red algal species, for instance, produces less red light-harvesting proteins under elevated ultraviolet radiation, thus lowering the light harvesting. The typical red colour of the alga fades and the plant gets white tips,” explains Prof. Dr. Christian Wiencke, marine biologist at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. “The algae additionally produce substances which react similar to melanin in human skins: mycosporine-like amino acids (MAAs) and other substances.” Melanin absorbs ultraviolet radiation and thus protects the human skin – at the same time, it gives a natural suntan.
The stratospheric ozone layer usually absorbs the major part of the hard and harmful short wave solar ultraviolet radiation. However, because of stratospheric ozone depletion, these dangerous rays increasingly penetrate down to the earth's surface and therefore also into the seawater.
Extensive biological experiments are presently conducted on this complex of problems at the German French Research Base AWIPEV on Spitsbergen. “We examine the harmful effects of ultraviolet radiation on algae and their protective mechanisms,” says Wiencke. The ultraviolet radiation particularly harms the algal photosynthesis and the inherited material. These organisms usually react with a decreased rate of growth or a reduced reproductive success.
The reproductive cells of the algae which drift through the water as unicellular propagules are particularly sensitive. Even low ultraviolet doses are damaging and inhibit their germination. “Our investigations show that the distribution of certain species of brown algae is limited by the ultraviolet radiation climate. These algae will be confined to deeper water layers if ultraviolet radiation increases.”
The research conditions on Spitsbergen are excellent for Wiencke and his colleagues: “We want to observe the changing of marine coastal ecosystems in view of global climate changes. Not only an elevated ultraviolet radiation plays a decisive role, but also the water temperature which is presently increasing due to the greenhouse effect. This increase in temperature is particularly obvious on Spitsbergen, in the Atlantic sector of the Arctic Ocean.”
Notes for Editors:
Your contact persons at the Alfred Wegener Institute is Prof. Christian Wiencke (phone: +49/471/4831-1338; email: Christian.Wiencke@awi.de).
Your contact person in the public relations department are Folke Mehrtens (phone: +49/471/4831-2007; email: Folke.Mehrtens@awi.de) and Magdalena Hamm (phone: +49/471/4831-1376; email: Magdalena.Hamm@awi.de).
The Alfred Wegener Institute carries out research in the Arctic and Antarctic as well as in the high and mid latitude oceans. The institute coordinates German polar research and makes available to international science important infrastructure, e.g. the research icebreaker “Polarstern” and research stations in the Arctic and Antarctic. AWI is one of 15 research centres within the Helmholtz Association, Germany’s largest scientific organization.
