UV test site
© Greg Hollis
Depletion of the ozone layer has meant that greater levels of ultraviolet B (UV-B) radiation have been reaching the earth's surface, particularly at higher latitudes. Scientists are concerned that increased levels of UV-B exposure could decrease frog populations.
In some cases, UV-B radiation may damage developing embryos. It may also depress immune system function, leading to greater vulnerability to disease. Some researchers suggest that UV-B exposure could work in combination with other possible causes of frog decline. For example, UV-B radiation can break down some pesticides, and the resulting breakdown products may be more toxic to frogs than the original compound.
What does UV-B exposure do to frogs?
UV-B exposure has been shown to cause deformation of embryos and lower hatching success. It is thought that such effects result from DNA damage, because UV-B radiation can damage DNA. Many species are generally able to repair certain amounts of such radiation-induced damage.
However, it is thought that some species are better able to repair the damage caused by UV-B radiation than others, and therefore better able to cope with the greater amounts of damage caused by higher levels of UV-B. This may be one of the reasons that different frog species are affected differently by UV-B radiation. For example, the eggs of the declining Green and Golden Bell Frog (Litoria aurea) are more affected than those of the non-declining Peron's Tree Frog (Litoria peronii) and Bleating Tree Frog (Litoria dentata).
The habitat and behaviour of different frog species can also make them more or less vulnerable to UV-B damage. For example, some species lay their eggs under hanging vegetation, which may shade them from the sun. As well, some waterbodies are high in dissolved organic carbon, which can block UV-B.