05+-+Animals

Animals of  Antarctica Plankton are microscopic or ganisms that float free  ly with oceanic currents and in other bodies of water. Plankton is made up of tiny plants (called **phytoplankton**) and tiny animals (called **zooplankton**).
 * Plankton ** [[image:0119-03.jpg width="344" height="230" align="left"]]

**Zooplankton**: Zooplankton are microscopic animals that eat other plankton
 * Phytoplankton**: Phytoplankton are primary producers. As the base of the oceanic food web,
 * Food Web ** : Plankton is the first link in the marine food chain; it is eaten by many organisms, including mussels, fish, birds, and mammals (like baleen whales).

Krill are small, shrimp-like crustaceans that swim in the seas. These pink, translucent animals congregate in large, dense masses called "swarms" or "clouds," that turn areas of the ocean's surface pink. Krill are very important in the food web since many animals eat them. There are about 85 species of krill, ranging in size from under 0.5 inch (1 cm) up to 5.5 inches (14 cm) long. The dominant krill in the southern polar oceans is the Antarctic krill which is up to 2.3 inches (6 cm) long and weighs about 0.035 ounces (1 g). Antarctic krill have a life span of about 5 to 10 years. Antarctic Krill is considered to be a keystone species, an organism upon which very many Antarctic predators depend.
 * Krill[[image:Plankton-Vanishing12jul05.jpg width="124" height="198"]] ** [[image:Krill_bw.gif width="375" height="280"]]
 * Diet ** : Krill eat phytoplankton, single-celled plants that float in the seas near the surface. Some tropical krill also eat zooplankton. Krill spend their days in the dark depths of the ocean (about 320 feet = 100 m deep), safe from their major predators (like baleen whales and sea birds). They swim to the surface each night to eat phytoplankton. They can fast (go without eating) for up to 200 days, shrinking during this time.
 * Anatomy ** : Krill have a hard exoskeleton, many legs (used for swimming and gathering food), and a segmented body. Females produce almost 1,000 eggs each summer; the eggs are laid at the surface, but fall to great depths. The hatchlings swim back to the surface to feed. Like all crustaceans, krill molt their exoskeleton as they grow.
 * Food Web ** : Phytoplankton is eaten by krill (and many other organisms). Krill are eaten by many organisms, including fish, squid, sea birds, and mammals (like baleen whales and some seals).

**Weddell Seal**

The Weddell seal is a large marine mammal that lives in Antarctic waters and on fast ice. It can dive underwater for over an hour, and has been seen at depths of 2,300 feet (700 m). This seal vocalizes noisily underwater, using a variety of calls to communicate with other Weddell seals. Most Weddell seal activity occurs at night. ** Diet ** : Weddell seals are **carnivores** (meat-eaters); they e at fish, squid, octopus, krill, and other small crustaceans. Seals don't chew their food; they swallow it in large chunks. They eat their food underwater.
 * Anatomy ** : The Weddell seal has short, thick fur. It grows to be up to 10 feet (3 m) long and can weigh up to 1,000 pounds (450 kg). The whiskers help the seal's sense of touch. Weddell seals use their large, strong, forward-pointing canine teeth to chew breathing holes in cracks in the ice. This seal can see well in dim light.
 * Predators ** : Weddell seals are hunted by killer whales (orcas), leopard seals, and people (they are used as food for sled dogs).
 * Name ** : These seals were named for the British Antarctic explorer James Weddell, who commanded British expeditions into the Weddell Sea (which is also named for him).

Antarctica Food Cycle