Life at the Poles: Eight Polar Animals That Face the Promise and Peril of Climate Change
When sea ice disappears some polar inhabitants advance, whereas others retreat
Life at the Poles: Eight Polar Animals That Face the Promise and Peril of Climate Change
- THIN-SHELLED: When carbon dioxide in the atmosphere dissolves in the ocean, it makes the water more acidic. This change in pH can interfere with shellfish, hindering their ability to build shells. Animals in Antarctic waters are particularly at risk because their shells tend to be precariously thin. "The first place on our planet where things should start losing their shells due to ocean acidification is Antarctica," says James McClintock, an Antarctic marine ecologist at the University of Alabama at Birmingham. Shown here is a limpet snail (Nacella concinna) in its thin shell, along with a common Antarctic sea star (Odontaster validus), which is a primary predator on the sea floor. Bill Baker
- ICE MINE: Adélie penguins [pictured] and emperor penguins only live in areas where there is sea ice. When the ice disappears, so do they. Adélie populations have decreased by 65 percent since the 1980s. But that's not the end of the story. In the Antarctic Peninsula other penguin species are replacing them. Chinstrap and gentoo penguins are fine with fishing off of land rather than floating sea ice and have been appearing where once only Adélies lived. In the future, a similar pattern might develop with seals. Elephant seals [seen here] and fur seals may end up with an advantage over Weddell seals, which spend most of their time swimming below sea ice hunting prey or hiding from predators. Hugh Ducklow
- KRILL KILL: Say hello to krill, shrimplike crustaceans that live in the sea. They are the principal food source for many animals, including penguins, seals and—especially—baleen whales. In the ocean near the Antarctic Peninsula, krill have plummeted about 80 percent in the past 30 years, which has affected the entire food chain there. "All these populations that depend on sea ice have apparently been declining, and the krill is apparently the key species," says Hugh Ducklow, a biological oceanographer who studies Antarctic food webs at the Marine Biological Laboratory's Ecosystems Center in Woods Hole, Mass. Krill eat diatoms and ice-associated algae, which means that they will be in hot, or at least warmer, water as temperatures rise. Where krill are decreasing, salps seem to be on the rise. These gelatinous, jellyfishlike animals do not have many predators, which means they do not help feed Antarctica like krill do. (This photograph is part of the traveling photo exhibit Irreplaceable: Wildlife in a Warming World".) Flip Nicklin / Minden Pictures
- PRETTY PLANKTON: Diatoms are single-celled algae that dominate the bottom of the food web along the Antarctic Peninsula, which is warming faster than anywhere else on Earth. Since 1950, the peninsula has increased in temperature about 6.1 degrees Fahrenheit (3.4 degrees Celsius). Some areas of the peninsula have lost 40 percent of their sea ice already. Water samples show that diatoms are on the decline, which is bad news for all the other living things that depend on them for food. The chain of diatoms [pictured] is magnified 600 times. They shine as light refracts through their silicon shells. Courtesy of Kristen Myers (the Marine Biological Laboratory and Brown University)
- SAND FLEAS OF THE SEAS: In the Arctic, another food chain stems from the sea ice itself. The bottom 0.8 inch (two centimeters) of the ice that floats in Arctic waters is home to hundreds of species of algae and tiny animals. These critters live within miniscule channels of seawater trapped in the ice. The amphipod [pictured], cousin of the sand flea, lives in the water just below the sea ice and depends on the ice's microscopic inhabitants as its source of food. Because some amphipods eat only from the sea ice, these diminutive crustaceans are at risk as temperatures rise. If amphipods have problems, so will other animals. Amphipods are a link in a food chain that sustains some of the largest Arctic mammals: They are dined on by cod, which are, in turn, eaten by ringed seals that are the staple of the polar bear diet. "If you see a polar bear what you're seeing is a whole food chain going down to the little critters," Bluhm says. Bodil Bluhm and Rolf Gradinger
- ON THE ROCKS: The polar bear [pictured], narwhal and hooded seal are the Arctic mammals most sensitive to climate change, according to a recent analysis. Hooded seals and polar bears are especially at risk because of their reliance on a sea ice habitat. And polar bears (which subsist almost entirely on seals) and narwhals (which seem to get most of their food from one bay) have picky diets that could spell trouble. NOAA Climate Program Office, NABOS 2006 Expedition
- BOTTOM-FEEDERS: Walruses, like other creatures that depend on food from the seafloor, may be in for trying times, says Brendan Kelly, a marine biologist who studies walruses and seals at the University of Alaska Southeast. In areas where the sea ice melts later in the spring, algae populations in the water grow. Then much of it drops to the ocean floor, becoming food for clams and crabs. But where sea ice melts earlier in the year, the algae bloom coincides with an increase in zooplankton (minute animals that float in the sea), which eat the most of the algae before it has a chance to drift to the bottom. In the future as the ice melts earlier, this second scenario may become more common, says Bodil Bluhm, a marine biologist who researches polar food webs at the University of Alaska Fairbanks. Animals that eat zooplankton, such as herring and minke whales, would increase in number. But it will be tougher for bottom-feeding marine mammals, such as walruses and gray whales. Captain Budd Christman, National Oceanic & Atmospheric Administration
