Deep Thoughts from UAB's Underwater Scientists
By Jo Lynn Orr
The Southern Ocean surrounds the frozen continent of Antarctica, and like its terrestrial counterpart, it is bone-chillingly cold and often coated in a thick layer of ice. Nevertheless, there is life in these waters: a sometimes eerie, frequently bizarre, and always fascinating catalog of creatures that often includes human divers—an adventurous team of UAB marine biologists led by Charles Amsler, Ph.D., and James McClintock, Ph.D.
The duo known as Chuck and Jim—along with Margaret Amsler, Jim’s research associate and Chuck’s wife, and a host of graduate students—have been studying animal and plant life in these frigid seas for more than two decades. But their specialty is not the familiar nature-special Antarctica of whales and penguins. Along with chemist Bill Baker of the University of South Florida, they research the chemical ecology of benthic, or bottom-dwelling, organisms—microalgae, seaweeds, sponges, tunicates, and other animals that grow attached to the ocean floor. “They’re things that can’t get up and run away when something’s trying to eat them,” explains Amsler.
Benthic organisms may not get around much, but their lives are anything but sedentary. Caught up in a raging battle for survival, they defend themselves with a host of mechanisms that could supply new weapons for our own war against cancer and other diseases. And their fragile habitat can serve as an early warning of the environmental changes to come in a warming world.
A view of the Antarctica peninsula from the research vessel Robert M. GouldDrugs from the Deep
The UAB team seeks to understand how organisms in these waters obtain better living through chemistry—that is, the often ingenious methods they have developed to avoid getting eaten by predators. “Many benthic plants and animals manufacture chemicals to make themselves taste bad, while others take more novel approaches such as slowing down the digestive process of predators so they can’t be eaten as fast,” Amsler says.
Exotic strategies abound down on the mean sands of the ocean floor, and these chemical choices are literally matters of life and death. “Organisms have to use resources to make chemical compounds to defend themselves, but these same chemicals, such as carbon or nitrogen, could instead be used to grow faster or make more babies—or make them quicker,” notes Amsler. “So there’s an evolutionary trade-off between maintaining defenses and trying to outgrow or outreproduce predators. In the big picture, much of our work focuses on trying to understand those trade-offs.”
Through the years, UAB’s Antarctica program has itself evolved to include drug-discovery missions. “When it comes to survival, benthic species engage in a sort of chemical warfare at the bottom of the sea,” McClintock says. “And we’ve found that chemical defenses in Antarctic marine organisms are just as common as they are in temperate and tropical systems. These have turned out to be very rich sources of potential new medications.”
Bill Baker sends all of the chemicals the polar biology team discovers to drug-testing agencies such as the National Cancer Institute (NCI). “We also work quite closely with Dr. Eric Sorscher at UAB’s Cystic Fibrosis Center, and he’s tested hundreds of our extracts,” McClintock says. Pharmaceutical companies also help examine the chemicals for potential uses, such as antibiotics.
Chuck Amsler collecting microalgaeSo far, the group’s most exciting discovery is a compound derived from a tunicate, or sea squirt. “Sea squirts are closely aligned with the vertebrate group that humans belong to, but they don’t look at all like animals with backbones,” McClintock notes. “Instead, they look like blobs, almost like sponges sitting on the ocean floor. We discovered one species of tunicate near Palmer Station in Antarctica, and the NCI extracted a compound from it that’s very, very potent against melanoma skin cancer. Researchers there were quite excited about it, and they’ve conducted a number of tests to see if it can be delivered from one tissue to another.”
The NCI is continuing to study the compound, and a private drug company is now conducting tests too, says McClintock. “Whether the research will go to the next stage of actual drug development, we don’t know, but we do know there’s a lot of interest in it. As scientists studying basic questions about ecology, we find it very rewarding to know that our work may have a positive impact on humanity by helping find a new drug to fight cancer.”
Bill McClintock, right, welcomes Bill Baker and Chuck Amsler back from their dive under the ice. Trouble on the Horizon
From their vantage point close to the southern pole, McClintock and Amsler are on the front lines of a new struggle for survival brought on by a global rise in temperatures. “The Antarctic Peninsula where we work is sort of the canary in the cage when it comes to climate change,” McClintock says. “Conditions there are changing very quickly, including an increase of about three or four degrees centigrade in air temperature in the last 30 years.”
That warming air is affecting the continent in increasingly visible ways. Much of the world’s press took notice when a chunk of ice the size of France broke free from the Larsen ice shelf in 2002. But this was not an isolated incident, notes McClintock. “Glacial recessions on the Antarctic Peninsula are quite noticeable and stunning, including the one behind Palmer Station where we work. Scientists can actually measure significantly greater rates of recession there over the past 10 or 20 years.”
As time passes, the effects of climate change are spreading from the geological to the biological realm. With ambient air temperatures rising near Palmer Station, populations of fur seals that used to gather north of the peninsula are migrating farther south. Polar biologist Bill Fraser, who has been studying a local population of Adelie penguins for 30 years, has predicted many changes as air temperature rises, and these have begun to come to pass. For instance, warmer Antarctic air contains higher levels of moisture, which brings more snowfall. This doesn’t sound like a big deal in a snow-covered region, but such changes are enough to upset delicate ecological balances.
Chuck and Maggie Amsler float in front of a natural ice bridge that was recently named in their honor.“Fraser took me to an island near Palmer Station where female Adelie penguins were sitting on their eggs buried in snow; all you could see were the heads of the females,” McClintock says. “The entire Adelie egg population that year didn’t hatch—the adults survived, but the eggs didn’t. Fraser is predicting that as climate changes occur, there will be more of these types of effects on penguins.”
Adelie populations are also starting to leave the Antarctic Peninsula, causing another group of biologists to speculate that the migration may be related to the disappearance of krill, their main food source. “Krill, which are tiny crustaceans, show signs of responding to the effects of climate change,” McClintock says. “As juveniles, these little shrimp-like animals live under the sea ice, where they graze on microalgae attached to the ice. But the pack ice is decreasing every year on the peninsula, which means there are fewer and fewer habitats where krill can develop and grow. So this food source of penguins, seals, and whales is also potentially being impacted.”
Light Spenders
The effects of climate change are also filtering down to the ocean floor. “The benthic communities we study are dominated by luxuriant forests of seaweeds whose growth is strongly influenced by available sunlight,” Amsler says. “Sea ice cover has changed dramatically over recent decades, and this undoubtedly is extending the environments where seaweeds can predominate.”
A pair of graduate students get ready to take an icy plunge with Chuck Amsler.Without a wall of frozen water above them to block the sun, these large plants might start to colonize areas that now have too little available sunlight, Amsler notes. “As more light becomes available, it might also affect their interactions with the animals that depend on them for food, for example by enabling them to invest more energy into the chemical defenses that deter herbivores from eating them than in the past,” he explains. While both Amsler and McClintock say such changes are not necessarily negative, climate change could bring dramatic environmental shifts compared to present-day communities.
Recently, a large spider crab was found living along the Antarctic Peninsula. McClintock points out that crabs are not native to this region, and the local populations have no defenses against them. “Because a number of additional large crabs have since been spotted, they may be permanently entering the ecosystem,” he says. “It’s possible they are moving south because their larvae can now survive the transit from South America into the warming waters of Antarctica, or they may have arrived in the ballast tanks of ships. Either way, a potentially invasive species is moving into the system that could change the ecology of these Antarctic sea floor communities tremendously.”
Pathway to Extinction?
A concern many share about climate change is the potential for entire species to be wiped out. This is not outside the realm of possibility, McClintock says. “Antarctic marine invertebrates have embryonic development stages that are extremely sensitive to incremental changes in water temperature,” he explains. “If the temperature is increased by even one or two degrees, then it may significantly shorten the developmental period. So the developmental cycles of animals that have adapted for the last 25 million years to a very low, stable temperature—and to developing when food is available for them—might not fully mature if their shortened larval development does not coincide with food available for growth.”
Earth’s polar regions tend to respond to climate change first, McClintock says, making them a harbinger of what could be in store for the rest of the planet. He points out that even though the environment is rapidly changing on the Antarctic Peninsula, most of the continent is not yet experiencing significant changes due to shifting climates. But it’s a completely different story for the northern Arctic region.
“The Arctic region is a sea covered with ice, as opposed to the Antarctic, which is a continent surrounded by ice,” McClintock explains. “And there is no doubt that the sea of ice in the Arctic is melting. Even more so than Antarctica, the Arctic is a canary in a cage. And to me the message to humans is, ‘Hey, wake up! Look at what’s happening in these polar environments, because it’s on its way to the temperate and tropical systems where most of us live.’”