Wildlife of Antarctica
The extreme weather of the interior contrasts to the relatively mild conditions on the Antarctic Peninsula and the subantarctic islands, which have warmer temperatures and more liquid water.
High densities of invertebrates also live in the ocean, with Antarctic krill forming dense and widespread swarms during the summer.
[9][10][11] Antarctic animals have adapted to reduce heat loss, with mammals developing warm windproof coats and layers of blubber.
Human activity has however led to the introduction in some areas of foreign species, such as rats, mice, chickens, rabbits, cats, pigs, sheep, cattle, reindeer, and various fish.
[14] The benthic communities of the seafloor are diverse and dense, with up to 155,000 animals found in 1 square metre (10.8 sq ft).
As the seafloor environment is very similar all around the Antarctic, hundreds of species can be found all the way around the mainland, which is a uniquely wide distribution for such a large community.
[15][16] The rocky shores of mainland Antarctica and its offshore islands provide nesting space for over 100 million birds every spring.
Together the snailfish, eelpouts and notothenioids (which includes cod icefish and several other families) account for almost 9⁄10 of the more than 320 described fish species in the Southern Ocean.
Although these species hunt underwater, they breed on land or ice and spend a great deal of time there, as they have no terrestrial predators.
[31] The New Zealand sea lion (Phocarctos hookeri), one of the rarest and most localized pinnipeds, breeds almost exclusively on the subantarctic Auckland Islands, although historically it had a wider range.
[34] Orcas, which do not migrate, nonetheless regularly travel to warmer waters, possibly to relieve the stress the temperature has on their skin.
[40] The swarms that form can stretch for kilometres, with up to 30,000 individuals per 1 cubic metre (35 cu ft), turning the water red.
[40] During the winter when food is scarce, adult Antarctic krill can revert to a smaller juvenile stage, using their own body as nutrition.
[39] Many benthic crustaceans have a non-seasonal breeding cycle, and some raise their eggs and young in a brood pouch (they lack a pelagic larvae stage).
[46] Nevertheless, many species from these southern oceans are extremely vulnerable to temperature changes, being unable to survive even a small warming of the water.
[46][47] Although a few specimens of the non-native great spider crab (Hyas araneus) were captured at the South Shetland Islands in 1986, there have been no further records from the region.
[46] Slow moving sea spiders are common, sometimes growing up to about 35 cm (1 ft) in leg span (another example of Polar gigantism).
Due to their low nutritional value, they are normally only eaten by fish, with larger animals such as birds and marine mammals only eating them when other food is scarce.
[55] Several species of marine worms are found in the Southern Ocean, including Parborlasia corrugatus and Eulagisca gigantea, which at lengths up to 2 m (6.6 ft) and 20 cm (8 in) respectively are examples of Polar gigantism.
[58] The largest is the whitish or dull yellowish Anoxycalyx joubini, sometimes called the giant volcano sponge in reference to its shape.
Long-term observation of individuals of this locally common glass sponge revealed no growth, leading to suggestions of a huge age, perhaps up to 15,000 years (making it one of the longest-lived organisms).
[63] Macrolichens (e.g., Usnea sphacelata, U. antarctica, Umbilicaria decussate, and U. aprina) and communities of weakly or non-nitrophilous lichens (e.g., Pseudephebe minuscula, Rhizocarpon superficial, and R. geographicum, and several species of Acarospora and Buellia) are relatively widespread in coastal ice-free areas.
[38] Sites with substrates influenced by seabirds are colonized by well-developed communities of nitrophilous lichen species such as Caloplaca athallina, C. citrina, Candelariella flava, Lecanora expectans, Physcia caesia, Rhizoplaca melanophthalma, Xanthoria elegans, and X.
[38] In the Dry Valleys the normally epilithic lichen species (Acarospora gwynnii, Buellia frigida, B. grisea, B. pallida, Carbonea vorticosa, Lecanora fuscobrunnea, L. cancriformis, and Lecidella siplei) are found primarily in protected niches beneath the rock surface occupying a cryptoendolithic ecological niche.
[38] Lichen species identified in recent research:[38] The greatest plant diversity is found on the western edge of the Antarctic Peninsula.
[3] While not being as widespread as lichens, they remain ubiquitous wherever plants can grow, with Ceratodon purpureus being found as far south as 84°30' on Mount Kyffin.
[65] The Mount Melbourne fumarole supports the only Antarctic population of Campylopus pyriformis, which is otherwise found in Europe and South Africa.
These plankton bloom annually in the spring and summer as day length increases and sea ice retreats, before lowering in number during the winter.
[72] Due to the historical isolation of Antarctic wildlife, they are easily outcompeted and threatened by introduced species, also brought by human activity.
[71] The Antarctic Treaty System regulates all activity in latitudes south of 60°S, and designates Antarctica as a natural reserve for science.
