Antarctic algae weather UV rays.

A group of Australian researchers reports that algae living underneath the sea ice along the coast of Antarctica show little evidence of damage caused by the annual ozone hole.

In past experiments, oceanographers have demonstrated that ultraviolet radiation hinders the growth of tiny marine plants, called phytoplankton, in Antarctic waters. These results concerned researchers because the ozone hole -- which forms each September over Antarctica and then dissipates in November -- allows extra amounts of ultraviolet radiation to reach Earth's surface. But the experiments could not determine whether 15 years of ozone holes have actually harmed phytoplankton in the wild.

Andrew McMinn of the University of Tasmania and his colleagues looked for changes by pulling up cores of sediments from Antarctic fjords near the Amery Ice Shelf. Using the decay of radioactive lead to date the sediment layers, they tracked the waxing and waning of algae species over the last 600 years. Their results suggest that the mix of algae species living beneath the sea ice does not show any unusual shifts following the first appearance of the Antarctic ozone hole in the late 1970s. McMinn and his colleagues report their findings in the Aug. 18 Nature.

The results do not give all Antarctic phytoplankton a clean bill of health, however. The species in these fjords may suffer less than others because the ozone hole develops at a time when extensive sea ice covers the water, blocking some of the ultraviolet light. Phytoplankton may fare worse if they live at the edge of the sea ice or in icefree regions.

The researchers also note that they see evidence of a decline in some species of sea-ice algae; but the changes do not exceed the swings that occurred long before the ozone hole, so they cannot blame the hole for the population decreases.