Abstract: The two poles occupy 14% of the surface area of the Earth’s biosphere, and together form the unique frozen cryosphere on Earth. Antarctica is an extremely large continent surrounded by the Southern Ocean, affected by the Antarctic Circumpolar Current. In contrast, the Arctic is composed of the Arctic Ocean surrounded by continents of Europe, Asia, and North America, and many scattered islands. The polar marine biosphere mainly includes two ecosystems: sea water and sea ice; sea ice is a unique ecosystem that exists in the polar regions. The polar oceans, sea ice, subglacial lakes and other environments contain many unknown viruses and their host microbial communities, which are an important driving force of global biogeochemical cycles. This article reviews the progress of viral diversity in the marine environments of the Arctic and Antarctica over the past two decades, which has been mainly unveiled by metagenomic technology. To date, our knowledge of dsDNA viromes has been significantly improved, however, our knowledge of ssDNA and RNA viromes is still very limited in polar marine environments. In general, our understanding of polar marine viruses is still in its infancy, and many novel scientific issues related to polar marine viruses need to be studied in more detail.

Key words: polar region, ocean, sea ice, virus, diversity, metagenomics