Wilson da Silva

Science journalist, feature writer and editor.

Mar. 30, 1997
Published on: Sunday Age
4 min read
Southern Bluefin tuna, an iconic fish species of the Southern Ocean

By Wilson da Silva

BIOLOGISTS have detected the first signs that the annual ozone hole over the Southern Hemisphere is harming fish life and causing mutations.

The amount of genetic damage in the fish studied was “higher than, or equivalent to, the amount of damage that has been found to be tumor-causing and even lethal,” Dr Kirk Malloy, a biologist at Boston’s Northeastern University, told The Sunday Age

“There’s no doubt that marine animals are enduring a lot of damage,” he said.

It is the first time scientists have proven that the higher rates of ultraviolet light being let in by the ozone hole, already known to stunt plant growth and lower some crop yields, is also affecting marine animals.

Dr Malloy and fellow researcher Dr William Detrich found genetic damage in more than 67 per cent of icefish eggs they studied in the waters around Antarctica. Of those eggs that developed into larvae, 80 per cent were found to have significant levels of damage to their DNA, or genetic blueprint.

If the DNA code is damaged or scrambled by ultraviolet rays, it becomes useless or gives faulty instructions, creating mutations.

Dr Malloy said that marine life in the Southern Ocean was not used to such levels of radiation and may not adapt fast enough to survive.

Whales, seals and penguins are likely to suffer less. As mammals, they gestate inside the womb and are not exposed to the harmful ultraviolet rays during early development. Fish eggs and larvae, however, float in the open sea during gestation.

It is likely that fewer fish are making it into adulthood and those that do will have higher rates of tumors or mutations.

“That has a ripple effect up the food chain,” Dr Malloy said. “It means that there’s less food available for the birds and mammals.”

Scientists have estimated that fish populations may be dropping by as much as 15 per cent in the Southern Ocean when the ozone hole opens up over Antarctica.

The ozone layer is a fragile shield of gas encircling the Earth that keeps out 90 per cent of the sun’s harmful ultraviolet rays. From October to December every year, a hole appears in the layer, bathing Antarctica and southern Australia in two to three times the normal amount of ultraviolet radiation.

Its depletion over the past 20 years has been traced to the release of industrial gases containing chlorine and bromine.

Research at Canberra’s Australian National University has shown that yields of crops such as peas, rice and soya beans can fall between 5 and 25 per cent when exposed to high rates of ultraviolet radiation.

Mr Malcolm Whitecross, the botanist who conducted the crop studies, said farmers should be breeding plant varieties that were more resistant to ultraviolet radiation.