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Antarctica – valued, protected and understood
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Photo: Chris Gillies
Seabed (benthic) communities
Seabed (benthic) animals include crustaceans, worms, echinoderms, shellfish (molluscs) and many other colourful, weird and wonderful beasts.
Underwater world an eye-opener for scientists
Habitat
The continental shelf around Antarctica 60 km to 240 km wide. This is relatively narrow. It ranges from very shallow areas of less than 50 m near the coast to areas deeper than 800 m. The average depth is 500 m.
Beyond the shelf, the Antarctic continental slope descends to over 3 km and levels out on the abyssal plains at depths of 3.7 km to 5 km.
Soft sediments (mud, sand and gravel) are the single largest habitat on the continental shelf, slope and abyssal plains. This kind of habitat probably covers over 90% of the seabed.
The animals and plants that live on the seabed are known as benthic communities. Benthic means pertaining to the seabed .
Soft sediments are home to diverse and abundant communities of animals. In some areas of Antarctica over 155,000 animals per square metre have been recorded.
Weird and wonderful animals
Many of the animals in soft-sediment communities in Antarctica are unusual in that they are very large. Gigantism is common in Antarctic benthic faunas.
The isopod Glyptonotus antarcticus grows up to 20 cm in length and 70 g in weight. In comparison, isopods in other parts of the world reach a maximum size of several centimetres. Glyptonotus antarcticus is found throughout Antarctica, the Antarctic peninsula and sub-Antarctic Islands from the intertidal to 790 m deep.
Many crustaceans (including Glyptonotus antarcticus ) have a non-seasonal breeding cycle. They incubate and raise their young in a brood pouch (marsupium). They release the young throughout the year.