Ozone alert; frogs, plankton and people show effects of ozone depletion.

What are green and slimy and not in your refrigerator? If you said "Frogs," you're right. But increasingly, they're not anywhere else, either.

Frogs have been hopping across the planet for more than 200 million years, right through the ice ages and right under the dinosaurs. They are survivors. But now, they are suddenly croaking. For the last five years, biologists have been alarmed at their dramatic decline.

Investigators at Oregon State University (OSU) decided to tackle the problem. The recent results of their four-year study provide strong evidence that the thinning of the Earth's ozone shield and the resulting increase in dangerous ultraviolet radiation may be the silent stalker of frogs and other amphibians throughout the world.

"We were shocked," said zoology professor Dr. Andrew Blaustein, author of the study. "We didn't think we'd find anything. When we got the results, we still didn't believe it. So we replicated it and now we believe."

In 1973, scientists discovered that human-produced chlorofluorocarbons (CFCs) decimate ozone when they break apart six to 25 miles above the Earth's surface. This ozone destruction allows the more biologically harmful ultraviolet-B rays (UV-B) to reach the Earth's surface. Every one percent decrease in ozone causes a 2.2 percent increase in DNA-damaging UV-B radiation. UV-B is also known to be the primary cause of human skin cancer and is linked to cataracts and immune system suppression. It also damages crops and marine algae. The best-known depletion--the ozone hole above Antarctica--measured nine million square miles in September 1992, a 15 percent increase over 1991. Less well known is the steady depletion of ozone over populated areas worldwide.

Science journal recently reported that UV-B radiation over Toronto, Canada had increased 35 percent per year in the winter and seven percent per year in the summer during the four-year frog study. (Ozone formation is triggered by sunlight, so there is always less ozone in the wintertime.) Toronto is at 44 degrees north latitude--the same latitude as the Oregon sites where Dr. Blaustein conducted his field experiments.

The OSU frog study was the first to prove that UV-B is now killing organisms living at mid-latitudes. "Damage to an animal means there probably will be an effect on humans," notes Blaustein. Scientists had widely believed that habitat loss and agricultural chemicals had been devastating amphibians. Indeed, these have taken their toll. But researchers had no explanation as to why populations also declined in relatively undisturbed regions.

Dr. John Hayes, OSU professor of agricultural chemistry, studied the eggs of 10 Oregon amphibian species. Of those 10, he found that the three with the best ability to repair or resist UV-B radiation were the Pacific tree frog, the Western toad and the Cascades frog.

Dr. Blaustein then studied the eggs of those three species in their natural habitat at Cascade Range lakes. Only 45 to 65 percent of the eggs of the Cascades frog and the Western toad hatched. But each had up to 25 percent more hatchlings when their eggs were shielded with a filter that blocked UV-B radiation. The third species, the Pacific tree frog, had a much stronger resistance: nearly 100 percent of their eggs hatched. Not surprisingly, while Pacific tree frog populations are stable, Cascades frog and Western toad populations have undergone such drastic declines that they are now official candidates for "threatened species" listing.

The study indicates that declining amphibian species lack the ability to protect themselves from increasing UV-B radiation. "The bottom line is that current levels of UV-B radiation in sunlight are killing amphibian eggs," says Dr. Blaustein. Amphibians have no hair, thick hide or feathers to shield them, nor are their eggs protected by leathery or hard shells. These characteristics make them vulnerable to UV-B.

According to herpetologist David Wake, "Amphibians are excellent indicators of environmental stress. Since they live in both aquatic and terrestrial ecological systems, they might tell us faster that something is wrong...they're an early warning system." Dr. Blaustein is now planning to research whether other species and life stages besides eggs also suffer from UV-B radiation.

Over Antarctica, the ozone layer thins by as much as 50 percent in the spring, when the destructive effects of CFCs in the atmosphere are maximized by weather conditions peculiar to this area. Simultaneously, the marine plankton there--the foundation of the ocean food chain--begin to bloom. UV-B has reduced plankton production by six to 12 percent. This may have already had an as-yet-unresearched impact on the marine food chain, extending from plankton to fish, to penguins, seals and whales.

Many scientists have praised the OSU study. "The implications are that the thinning of the ozone layer may already be affecting wildlife," reflects Dr. Soule, chairman of environmental studies at the University of California at Santa Cruz. "If further work supports that conclusion, it means that we can't rest on our laurels. We'll have to do something about repairing the ozone layer, rather than doing what governments are doing, which is just waiting for it to stop getting worse." The New York-based Ozone Society also takes a proactive approach. Their prototypical "middle atmosphere platform" sweeps the middle atmosphere and neutralizes the chlorine that destroys ozone molecules. They've also designed a meter for gauging UV levels, another measuring sunscreen protection, and for clothing with UV-protective qualities.

Human-related research gives us a hint of our personal stake in this picture. A study last year by the National Center for Atmospheric Research in Boulder, Colorado found that an increase in UV-B radiation could result in skin cancer rates rising 10 to 20 percent in the next few decades in the Pacific Northwest. And a U.N. report released in February 1992 confirmed that ultraviolet radiation's "profound influence" on weakening the human immune system might lead to an increase of infectious diseases, including AIDS. It also forecasted 1.6 million new cases of cataracts and 300,000 of skin cancer by the year 2000.

Australia, where frog species are in serious decline, is one area where the ozone layer has been most severly diminished. UV-B levels are announced on the local news along with the weather. Cancer checks are available for free on many local beaches. In most areas, two out of three Australians will develop skin cancer. But in the state of Queensland, where ozone depletion is greatest, this figure rises to three out of four.

Although the myth of the "healthy tan" has been debunked by scientists everywhere, it's not simply a matter of avoiding sunbathing on the beach. Eighty percent of UV-B exposure occurs during such everyday activities as running errands, driving the car or sitting by a window (glass does not block UV-B). Physicians recommend sunscreens with SPF-15 and UV-protective sunglasses.

Americans aren't quite as well informed about how our own disappearing ozone is now impacting our health. In 1935, an American's chance of developing malignant melanoma, the most serious skin cancer, was one in 1500. By 1991, it was one in 150. And by the year 2000, the odds will be one in 75.

Ultimately, only a massive effort to protect the ozone layer will halt these frightening trends. Harry Darlington, president of the Ozone Society, urges us to "move forward swiftly. We don't have time to 'wait and see' in the face of concrete evidence of growing ozone depletion, growing radiation and the growing ill effects on the health of people and all life forms." Contact: The Ozone Society, 666 Fifth Avenue, New York, NY 10103/[phone].