Is solar UV frying fish?


20 March 2007

Marine and freshwater organisms could be facing damage due to increasing levels of ultraviolet (UV) radiation, according to a United Nations (UN) commissioned review.

The news is reported in the latest edition of the Royal Society of Chemistry journal Photochemical & Photobiological Sciences. 

Aquatic ecosystems produce over half the biomass of the Earth and are an integral part of the planet's biosphere. 

The international team behind the review is worried that the depleted ozone layer has exposed these ecosystems to harmful levels of UV radiation, particularly in polar regions where the ozone layer is the thinnest.

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.

Additionally, the annual phytoplankton boom, which supports the entire Antarctic aquatic food chain, is currently protected from UV damage by a layer of sea-ice.

Warmer climates would mean sea-ice melts earlier, increasing UV exposure. These plankton are particularly vulnerable to UV damage as the low temperatures slow their repair mechanisms.

False-colour map representing the Earth's carbon metabolism

The relationship between UV levels and their negative impact on aquatic ecosystems works both ways.

A team of scientists from Germany, India and America compiled the review. It comprised hundreds of separate studies into to the effects of UV radiation, covering organisms from plankton to frogs and fish.

The findings highlight that while the effects of UV radiation on entire ecosystems are difficult to measure and model, the impact on individual species can be dramatic.

Numbers of frogs, toads and other amphibians have fallen across the world over the last 10 years. And while the exact cause is a complex combination of factors, the review highlights more than 50 research papers implicating UV radiation. 

The study is part of a wider United Nations Environmental Programme (UNEP) report on interactions between ozone depletion and climate change.

Every few years, UNEP produces a report for parties to the Montreal Protocol - the 1987 international agreement to phase out production of most ozone depleting compounds, such as CFCs, by 2000. The report is subsequently published in Photochemical & Photobiological Sciences, to make it available to the entire scientific community.

Janet Bornman, co-chair of the Environmental Effects Assessment Panel of the UNEP and co-ordinator of the report, said: "It is hoped that the publication will stimulate the scientific community to continue working on the gaps in knowledge that still exist.

"We hope that it will help keep scientists aware of their involvement in the protection of the environment for all forms of life on Earth".

with thanks to James Mitchell Crow for the original article

Link to journal article

Effects of solar UV radiation on aquatic ecosystems and interactions with climate change
D.-P. Häder, H. D. Kumar, R. C. Smith and R. C. Worrest, Photochem. Photobiol. Sci., 2007, 6, 267
DOI: 10.1039/b700020k

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