Study highlights harmful effects of UV light on marine and freshwater life
Ultraviolet radiation is not just a cause for concern for us humans; its harmful rays are also damaging many of the world's marine and freshwater organisms, according to a United Nations (UN) commissioned review.
The review, which was compiled by a team of German, Indian and US scientists, is an analysis of several hundred separate studies into the effects of UV radiation, covering organisms from plankton to frogs and fish. It is published in the latest edition of the Royal Society of Chemistry journal Photochemical & Photobiological Sciences.
Ozone and aerosols provide the primary filter in the atmosphere that reduces damaging UV radiation before it reaches the Earth's surface. With the ozone layer depleting due to pollution, these harmful ways are finding their way through.
Although it is difficult to measure the effects of exposure on the entire ecosystem, the review gives evidence of how individual marine and freshwater species are touched.
Organisms found in polar regions, where the ozone layer is at its thinnest, and in clear lakes and alpine regions, may be the most vulnerable, write the authors of the review.
Among those at risk are Phytoplankton, which are by far the biggest biomass producers in the oceans, and form the basis of the aquatic food webs. Their productivity rivals that of all combined land ecosystems. The review points to a number of studies which show how high levels of solar radiation significantly inhibit photosynthesis, nutrient uptake and growth in some species.
In sea urchins, UV radiation causes cell-self destruction (apoptosis) in developing embryos, while for some frogs, the harmful rays are thought to be a contributing factor to malformation and mortality.
Fish are also at risk from UV radiation. Although the primary causes of the decline in the world's fish stocks are overfishing, predation and poor food supply for larvae, scientists believe that increased temperatures and exposure to UV light may contribute further to that decline.
Solar UV radiation has been shown to induce DNA damage in the eggs and larvae of the Atlantic cod, while artificial UV causes massive apoptosis in the larval embryos of Japanese flounders.
Aquatic ecosystems produce more than 50% of the biomass on our planet, and are key components of the Earth's biosphere. The review's findings are therefore worrying since any UV damage could have serious consequences for the productivity of these ecosystems.
There could also be wider implications for climate change, since if UV damage cuts marine ecosystem productivity, the oceans' capacity to mop up the greenhouse gas carbon dioxide would fall. This extra atmospheric CO2 could then add to global warming.
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