Ozone Depletion: A Sunburn on the Sea

When I first learned to dive, my father taught me not to splash through the surface as I entered the water. Slamming the surface could hurt the body, especially the ears, if a diver were to land the wrong way. Splashing was also noisy, disruptive to the sea life we wished to observe. So our habit became to slip into the water slowly, to savor that comforting initial contact and caress of the sea, to respect the first touch of the water.

But today the surface of the ocean requires more than a diver’s reverence. It needs protection, for the surface is the key to the treasury of ocean life, the ocean’s face to the sun. And it is ironic that the sun’s energy, the ageless ally of life in the sea, could become its enemy in our time--without a fully functioning ozone layer in the atmosphere to screen out harmful ultraviolet radiation.

We have heard much about how ozone depletion can cause sunburn, skin cancer, weakened human immune systems and ruined agricultural crops. But we are also seeing that too much ultraviolet light reaching the ocean could seriously damage life at the vital ocean surface.

The Earth’s atmosphere is a relatively thin shield. Dr. Thomas Coohill, president-elect of the American Society of Photobiology, has said, “If the Earth were a peach, the atmosphere would be less than the fuzz on the peach.”

Ozone, a three-atom form of oxygen, is part of this protective “fuzz.” In the lower atmosphere, if we breathe it in smog, ozone is a pollutant dangerous to our health. But in the stratosphere, ozone absorbs harmful solar rays. Thus, though invisible and colorless, ozone provides a critical filter.

But ozone molecules can be split apart by man-made chemicals known as chlorofluorocarbons used in solvents, refrigerants, aerosols and foams. Rising into the stratosphere like bullets, these chemicals shatter ozone molecules, thus breaking down the ozone layer. Worse, CFCs linger in the skies, doing damage long after we may stop using them on Earth.

For the ocean, the effects can be insidious. Some plants and animals live at the surface itself, some just below the surface, and some at the farthest depths to which light can reach, depending on the clarity of the water. In marine biology terms, the surface of the sea extends down roughly 100 meters in the open ocean, but much less in the fertile coastal areas.

This sunlit layer of water is a world in itself. Microscopic ocean plants called phytoplankton conduct their business of living--photosynthesis, the conversion of light to food. By taking in the radiant energy of the sun and chemicals in seawater, phytoplankton produce their nourishment. Thriving phytoplankton are in turn eaten by microscopic animals and small creatures, such as the shrimp-like krill, which in turn are eaten by fish, crabs, penguins, seals and on up the steps of the food chain.

In other words, the ocean surface is a community of creatures whose basic fuel is sunlight. If, to symbolize that surface, we draw a line on a blank piece of paper, the thickness of that line would contain plants and animals that can live only within the thickness of that line.

Erase that line and most life in the ocean dies.

The subtle link between dangerous ultraviolet light and the life of the sea has not yet been widely studied. Some investigations have been conducted in temperate and subtropical zones, and Dr. Sayed El-Sayed of Texas A&M; University has conducted the first experiments in Antarctic waters, fortunately before the recent oil spills earlier this year.

He found that ultraviolet radiation definitely inhibited photosynthesis of phytoplankton, and that the unwanted rays could penetrate, in Antarctica’s clear waters, at least to 20 meters. Since phytoplankton must seek sunlight in order to live, they become “sitting ducks,” as Dr. El-Sayed put it, for unfiltered sunlight. He added, “We have to be careful not to extrapolate too much from my work, but I have appealed to other scientists to go ahead and follow up, to gather more vitally needed information.”

Recently in London, the European Economic Community plus the United States, which account for 75% of worldwide CFC production, agreed to ban all such production by the year 2000. Then, just days later, France convened an international conference in The Hague calling for a supra-national United Nations agency with enforcement power to address global environmental problems. These meetings, of course, were very encouraging signs of international action at last to confront our planet’s environmental deterioration.

But feeling satisfied with handshakes and agreements on paper would be a dangerous luxury. Protecting the ozone layer will require the constant cooperation of science, industry, politics and people to make CFC substitutes universally available.

Otherwise, life on Earth could slip through our hands as easily as the silky ocean slips through my fingers.