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The Arctic sea ice covers less area in the summer than in the winter. The multi-year (i.e. perennial) sea ice covers nearly all of the central deep basins. The Arctic sea ice and its related biota are unique, and the year-round persistence of the ice has allowed the development of ice endemic species, meaning species not found anywhere else. There are differing scientific opinions about how long perennial sea ice has existed in the Arctic. Estimates range from 700,000 to 4 million years. ==Endemic species== The specialized, sympagic (i.e. ice-associated) community within the sea ice is found in the tiny (mostly <1mm diameter) liquid filled network of pores and brine channels or at the ice-water interface. The organisms living within the sea ice are consequently small (<1mm), and dominated by bacteria, and unicellular plants and animals. Diatoms, a certain type of algae, are considered the most important primary producers inside the ice with more than 200 species occurring in Arctic sea ice. In addition, flagellates contribute substantially to biodiversity, but their species number is unknown. Protozoan and metazoan ice meiofauna, in particular turbellarians, nematodes, crustaceans and rotifers, can be abundant in all ice types year-round. In spring, larvae and juveniles of benthic animals (e.g. polychaetes and molluscs) migrate into coastal fast ice to feed on the ice algae for a few weeks. A partially endemic fauna, comprising mainly gammaridean amphipods, thrive at the underside of ice floes. Locally and seasonally occurring at several 100 individuals m-2, they are important mediators for particulate organic matter from the sea ice to the water column. Ice-associated and pelagic crustaceans are the major food sources for polar cod (''Boreogadus saida'') that occurs in close association with sea ice and acts as the major link from the ice-related food web to seals and whales. While previous studies of coastal and offshore sea ice provided a glimpse of the seasonal and regional abundances and the diversity of the ice-associated biota, biodiversity in these communities is virtually unknown for all groups, from bacteria to metazoans. Many taxa are likely still undiscovered due to the methodological problems in analyzing ice samples. The study of diversity of ice related environments is urgently required before they ultimately change with altering ice regimes and the likely loss of the multi-year ice cover. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Arctic sea ice ecology and history」の詳細全文を読む スポンサード リンク
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