It is striking how closely the damage to the fish eggs tracked with the increased intensity of ultraviolet light. The studies were done on cruises in waters around the Antarctic Peninsula, the finger of land that juts up toward South America. The protective ozone layer over Antarctica has thinned over the past two decades, as human-created chemicals called chlorofluorocarbons have risen to the stratosphere and helped to destroy ozone. Antarctica's ozone levels typically drop to less than half of normal during the spring ozone hole, allowing wavelengths of sunlight harmful to life to penetrate to the earth's surface and into ocean waters. The ozone layer has also thinned, although less so, in temperate regions.
Ozone depletion is predicted across even broader areas of the globe over the next century.
The excess ultraviolet light may slow a fish's growth, hamper cellular processes such as transcription and mitosis, and divert precious energy to DNA repair. Organisms such as icefish and krill, which breed in spring and release their eggs into ocean waters at the peak of the ozone hole, can repair DNA more than twice as fast as rockcod and other fish that breed in winter. The researchers' next step is to explore whether the DNA damage actually does hamper the animals' ability to survive.