ASU Research E-Magazine: Green Sunscreen

When Thomas “Tad” Day says he’s going south for the winter, he really means it. In fact, he goes about as far south as you can get—Antarctica.

Day is an assistant professor of plant biology at Arizona State University. For the past three winters, he has trekked down to the end of the world to study how plants respond to increased exposure to ultraviolet (UV) light.

Why Antarctica? The chilly continent is an ideal location for Day’s work because it lies beneath the biggest ozone hole in our planet’s atmosphere. Since ozone helps to filter out ultraviolet light before it reaches the Earth, areas under ozone holes receive an extra dose of the dangerous radiation.

Scientists already know ultraviolet exposure can lead to skin cancer and cataracts in humans. Laboratory studies have shown that UV also adversely affects plants. Day and his students are the first group to test this hypothesis under a natural ozone hole.

“It’s really difficult to simulate ozone depletion effects with artificial UV lamps,” Day says. “Plants are pretty sensitive to the type or quality of radiation they receive.”

So, for the past three years, Day has gathered a group of students and trekked down to Palmer Research Station on the Antarctic peninsula. In late 1997, his team included postdoctoral student Fusheng Xiong, graduate student Christopher Ruhland, and undergraduate William Karl.

Aerial view of one of the Antarctic islands known as the Stepping Stones

Their “laboratory” is a small island in a group known as the Stepping Stones, near Palmer Station. The group travels to the site in a motorized, inflatable raft called a Zodiac. They only spend about half their days at the island, because severe weather often prevents them from taking out the Zodiac.

When they do go to the site, Day’s team studies the effects of UVB light—the most damaging type of ultraviolet light—on two native plants. Antarctic pearlwort and Antarctic hair grass are the only vascular (leafy) plant species found in all of Antarctica.

Day’s findings support earlier studies that claim UVB is harmful to plants. However, the damage is probably less than expected because plants in the wild produce their own kind of “sunscreen,” called flavanoids. Flavanoids screen out some of the more dangerous UVB-type radiation. The plants did not produce these protective flavanoids in earlier lab studies.

“Lab studies tend to overestimate the damaging effects of UV because it’s almost impossible to provide as much visible light as there is outside,” Day says.

He explains that most plants and animals do not have sensory organs to detect UV levels. Instead, their bodies use the amount of visible light as a cue to produce flavanoids. If the laboratory cannot produce visible light that is as bright as sunlight, the plants don’t “know” that the UV levels are higher. As a result, they do not produce more flavanoids.

Antarctic pearlwort is plant that resembles a green, round cushion.

The Antarctic pearlwort and hair grass are different from many plants. They provide a very uniform coverage of flavanoids, which better protects them from UV radiation. Think of the best way to apply sunscreen before going to the beach—you will get better protection by spreading lotion all over your body rather than dotting and dabbing it on in only a few places.

Day hopes that plant breeders and geneticists can use this information to breed more UV-resistant crops in the future.

“We’re trying to find where the weak links are in plants,” he says. “Most plants aren’t like [the Antarctic pearlwort and Antarctic hair grass]. Are their genes responsible for that? Can we take those genes and put them into crop plants?” These are important questions that require more study.

Day has also started to look at the effects of global warming on the Antarctic plants. The Antarctic peninsula is experiencing rising air temperatures. During the past 40 years, temperatures have increased by about 2.5 degrees Celsius (4.5 degrees Fahrenheit). The cause of this warming is unknown at this time.

Day’s team has found that slight increases in temperature actually help the plants. This benefit stops when temperatures around the plants exceed about 15 degrees Celsius.

Antarctic iceberg

Day says that the temperature along the ground (where the plants grow) can get up to 30 degrees Celsius in the summer on the Stepping Stones. The plants stop photosynthesizing and growing.

“They essentially shut down,” he says. “For some reason, they can’t deal with these high temperatures. If the warming trend continues, it may get to the point where these plants can no longer survive there.”

Day’s work also has been used to help educate schoolchildren about environmental issues. The “Live from Antarctica” program, a joint project from the National Science Foundation, NASA and PBS, educates kids about Antarctica and the environment.

In January 1998, PBS aired the first ever live broadcast from Antarctica, direct from Palmer station. Kids across the United States were able to address questions to Antarctic researchers from their own classrooms. They also got to glimpse what life is like at Palmer Station.

Palmer is smaller than other U.S. research stations in Antarctica. While McMurdo Station can house 2,000 people at a time, and the South Pole can accommodate 150, Palmer only houses about 42. About half the population of Palmer consists of support people who run the power plant, cook, operate the radio, maintain the computers, and do other maintenance jobs. The other half are scientists.

Antarctic hairgrass has long leaves that point out in all directions.

“Space is a big problem at Palmer,” Day says. Most people there bunk four to a room, and the rooms are smaller than a typical college dorm. To keep order in cramped quarters, everyone does his or her fair share.

For example, Saturday is “House Mouse.” Everyone pitches in for a weekly cleaning. And although Palmer residents can expect three prepared meals a day, they have to bus their own dishes and take a kitchen-cleaning shift.

“The cooks cook, but they don’t clean,” Day adds.

“One of the hardest things is when people want to get away. Bad weather often keeps everyone cooped up indoors. Even on good days, you can’t travel much farther than a half mile along the glacier, because it becomes heavily crevassed.”

Communication with the rest of the world is limited, too. The only way to get to Palmer is on an icebreaker that travels between the station and Punta Arenas, Chile. The ship visits about 10 times a year, carrying food, fuel, and people. When the ship is gone, the only way to communicate beyond the station is via e-mail during a daily two-hour time slot. The messages are communicated via satellite at a speed of 300 baud (by contrast, most modems on the market today run at 33,600 baud). The one telephone at the station is reserved for emergencies.

Palmer’s inhabitants live in cramped quarters. But they also form a strong feeling of camaraderie. Day, who plans to spend at least two more winters at the station, claims, “Everybody’s kind of a big family there.” —Diane Boudreau