Ozone hole kills sea life, says scientist

The ozone hole over Antarctica is having a bigger impact on life than realised, scientists believe.

The layer, 24km above Earth, acts as a shield against ultraviolet (UV) radiation.

An annual thinning of the ozone over Antarctica allows significantly more UV light to reach the ocean and damage DNA.

New Scientist magazine reported yesterday that an analysis of east Antarctic waters had shown that high levels of UV light could significantly reduce phytoplankton blooms.

These microscopic plant cells at the bottom of the food chain provide food for zooplankton, tiny marine animals that are eaten by more than 50 species of seabirds and by fish and sea mammals ranging from sardines to whales.

"If you have a substantial reduction in the amount of plant material, that's going to have all sorts of knock-on effects for the rest of the food web," said Andrew Davidson, of the Australian Antarctic Division in Kingston, Tasmania.

His team studied the marginal ice zone around Antarctica, which produces between a quarter and two-thirds of the Southern Ocean's phytoplankton.

The team used satellite data to study levels of chlorophyll, an indicator of phytoplankton levels, and ozone concentration in five regions during November and December, from 1997 to 2000.

They considered only data for periods when there were at least six cloudless days out of 10.

Total chlorophyll increased, as expected, but when ozone levels thinned, chlorophyll accumulation fell.

Dr Davidson said it had been difficult to pinpoint the effect of UV, because the amount of plant material in Antarctic waters varied by up to 25 per cent from year to year.

The findings have been challenged by an American scientist, who said average chlorophyll concentrations in Antarctic waters under the ozone hole had not changed since the late 1970s.

Kevin Arrigo, associate professor of geophysics at Stanford University in California, said: "This suggests to me that the ozone hole is having very little impact on overall chlorophyll concentrations in the Antarctic."

- NZPA