The ozone hole over Antarctica has been implicated for the first time in harm to animal life. A provocative report in the current issue of the Proceedings of the National Academy of Sciences suggests that increased exposure to ultraviolet (UV) light, from a thinning of the ozone layer caused by synthetic chlorofluorocarbons, may damage the DNA of fish.
While others have documented UV's detrimental impact on phytoplanktons, scientists at Northeastern University in Boston decided to look further up the food chain. They examined the DNA of fish eggs and larvae collected in 1994 when the ozone hole is most pronounced: from mid-October to mid-November, the early austral spring. They found that the fish cells had high levels of DNA lesions called cyclobutane pyrimidine dimers--errors that could impede transcription and mitosis. The extent of injury they found, says senior author William Detrich III, a molecular marine biologist at Northeastern, would be lethal in other organisms.
Although test tube experiments have shown that as much as half of UV-induced injury is repaired within an hour, the scientists speculate that this damage-repair cycle may extract a heavy toll over time. Given that many organisms higher on the food chain consume the study's subjects, the finding "suggests that we may be impacting the ecosystem," Detrich says, by affecting the food supply and, possibly, the long-term viability of particular species. Adds Susan Weiler, executive director for the American Society of Limnology and Oceanography, "They've taken things to the next level up and have found an effect."
The scientists acknowledge that a lack of historical data makes it hard to pin the blame on the ozone hole. The next step, says visiting scientist Kirk Molloy, is to "try to better correlate the damage to ozone depletion." Molloy and others hope to collect data at the end of the austral summer, when the ozone hole has disappeared. A comparison of damage levels, he says, could reveal the smoking gun.