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Is UV-B radiation a factor in the decline of frogs and other amphibians?

Last updated 18 January 2002
Originally answered 18 January 2002

Full Question

Is UV-B radiation a factor in the decline of frogs and other amphibians?

Answer

According to the 1998 United Nations Environment Program Assessment: Environmental Effects of Ozone Depletion:



“Possibly. Amphibian populations are in serious decline in many areas of the world, and scientists are seeking explanations for this. Most amphibian population declines are probably due to habitat destruction or habitat alteration. Some declines are probably the result of natural population fluctuations. Other explanations for the population declines, as well as the reductions in range of habitation, include disease, pollution, atmospheric changes and introduced competitors and predators. UV-B radiation is one agent that may act in conjunction with other stresses to adversely affect amphibian populations. Field studies in which embryos of frogs, toads, and salamanders were exposed to natural sunlight or to sunlight with UV-B radiation removed have shown conflicting results. Some studies resulted in increased embryonic mortality after UV-B exposure, whereas others show that current levels of UV-B radiation are not detrimental. Factors such as water depth, water colour, and the dissolved organic content of the water at the sites of egg deposition effectively reduce UV-B penetration through the water and reduce exposure to UV-B radiation at all life history stages. Biotic factors, such as jelly capsules around eggs, melanin pigmentation of eggs, , and colour of larvae and metamorphosed forms, further reduce the effects of UV-B exposure.”


The above entry is posted under the following topic(s): Impacts of Ozone Depletion

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Does water protect aquatic organisms from UV exposure?

Last updated 17 January 2002
Originally answered 17 January 2002

Full Question

Does water protect aquatic organisms from UV exposure?

Answer

Well, according to FAQ # 9 from the “Frequently Asked Questions about Stratospheric Ozone Depletion” published in “Environmental Effects of Ozone Depletion: 1998 (United Nations Environment Program Assessment), (see: http://www.gcrio.org/ozone/toc.html), not necessarily. It depends on how clear the water is, and where in the water column the organism lives.

“No. Pure water is quite transparent to UV radiation; a beam of UV-B radiation must travel over one-half kilometre through pure water in order to be completely absorbed. Natural waters do contain UV-absorbing substances, such as dissolved organic matter, that partly shields aquatic organisms from UV-B, but the degree of shielding varies widely from one water body to another. In clear ocean and lake waters ecologically-significant levels of UV-B can penetrate to several tens of meters; in contrast, in turbid rivers and wetlands UV-B may be completely absorbed within the top few decimetres. Most organisms in aquatic ecosystems, such as phytoplankton, live in the illuminated euphotic zone close to the water surface where exposure to UV-B can occur. In particular, UV-B radiation may damage those organisms that live at the surface of the water during their early life stages.”


The above entry is posted under the following topic(s): Impacts of Ozone Depletion

To link uniquely to the question and answer displayed above, please refer to this page where they are permanently posted.

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