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| image = Akanko.JPG| caption = The view from Mount Oakan (July 2008)|alt=The view from Mount Oakan (July 2008)| image_bathymetry =| caption_bathymetry =Kushiro Subprefecture>Kushiro, Hokkaidō, Japan|pushpin_map=Japan43614455type:waterbody_region:JP|display=inline,title}}Dimictic lake>Dimictic| inflow =| outflow = Akan River148mi2|abbr=on}}| basin_countries = Japan| length =| width =13acre|abbr=on}}17.8ft|abbr=on}}44.8ft|abbr=on}}0.23mi3|abbr=on}}| residence_time =25.9mi|abbr=on}}420ft|abbr=on}}| islands = 4: Ōjima, Kojima, Yaitai Island, Chūrui IslandKushiro, Hokkaidō>Kushiro| frozen = December to April| extra = {{Designation list }}{{nihongo|Lake Akan|阿寒湖|Akan-ko}} is a lake in Kushiro, Hokkaidō, Japan. It is located in Akan National Park and is a Ramsar Site.WEB,www.ilec.or.jp/database/asi/dasi21.html, Data Summary: Akan-ko (Lake Akan), World Lakes Database, International Lake Environment Committee, 2009-05-18, dead,www.ilec.or.jp/database/asi/dasi21.html," title="web.archive.org/web/20120420191210www.ilec.or.jp/database/asi/dasi21.html,">web.archive.org/web/20120420191210www.ilec.or.jp/database/asi/dasi21.html, 2012-04-20, WEB,www.env.go.jp/en/nature/npr/ramsar_wetland/pamph/akanko_10.pdf, Ramsar Sites in Japan - Akan-ko, Ministry of the Environment (Japan), Ministry of the Environment, 24 March 2011,

History

Volcanic activity formed the lake some 6,000 years ago, when a lava dam was formed. The lake used to have a clarity of 8–9 meters in the 1930s. Pollution from local hotspring resorts has decreased the transparency to 3–4 meters.WEB,www.ilec.or.jp/database/asi/asi-21.html, AKAN-KO (LAKE AKAN), World Lakes Database, International Lake Environment Committee, 2009-05-18, dead,www.ilec.or.jp/database/asi/asi-21.html," title="web.archive.org/web/20120305044513www.ilec.or.jp/database/asi/asi-21.html,">web.archive.org/web/20120305044513www.ilec.or.jp/database/asi/asi-21.html, 2012-03-05,

Flora and fauna

The lake is famous for the marimo (Aegagropila linnaei), aggregations of algae that form into spherical shapes 2–30 cm in diameter. Other flora of the lake include the following:

• Phragmites communis
• Nuphar sp.
• Potamogeton crispus
• Hydrilla verticillata
• Myriophyllum verticillatum
• Vallisneria gigantea
• Melosira italica
• Asterionella formosa
• Synedra

Kokanee salmon (Oncorhynchus nerka) are native to Lake Akan.Other fauna of the lake include the following:

• Zooplankton:
  • Daphnia longiremis
  • Bosmina coregoni
  • Eurytemora affinis
• Bottom:
  • Chironomus plumosus
  • Tubificidae
• Fish:
  • Common carp
  • Crucian carp
  • Pond smelt
  • Big-scaled redfin

Climate

{{Weather box|width = auto|collapsed = Y|single line = Y|metric first = Y|location = Lake Akan (1991−2020 normals, extremes 1977−present)|Jan record high C = 6.1|Feb record high C = 10.8|Mar record high C = 16.5|Apr record high C = 28.3|May record high C = 35.5|Jun record high C = 34.5|Jul record high C = 34.9|Aug record high C = 33.9|Sep record high C = 31.4|Oct record high C = 24.5|Nov record high C = 19.0|Dec record high C = 11.8|Jan record low C = -30.2|Feb record low C = -30.7|Mar record low C = -26.6|Apr record low C = -20.9|May record low C = -7.5|Jun record low C = -3.3|Jul record low C = 1.8|Aug record low C = 3.2|Sep record low C = -1.2|Oct record low C = -7.6|Nov record low C = -17.3|Dec record low C = -26.9|Jan high C = -4.2|Feb high C = -3.1|Mar high C = 1.4|Apr high C = 8.1|May high C = 15.1|Jun high C = 18.9|Jul high C = 22.3|Aug high C = 22.8|Sep high C = 19.0|Oct high C = 13.2|Nov high C = 5.8|Dec high C = -1.4|Jan mean C = -10.0|Feb mean C = -9.4|Mar mean C = -4.2|Apr mean C = 2.3|May mean C = 8.5|Jun mean C = 13.1|Jul mean C = 17.1|Aug mean C = 18.0|Sep mean C = 14.0|Oct mean C = 7.5|Nov mean C = 0.7|Dec mean C = -6.5|Jan low C = -16.7|Feb low C = -16.8|Mar low C = -10.8|Apr low C = -3.3|May low C = 2.3|Jun low C = 8.0|Jul low C = 12.9|Aug low C = 13.9|Sep low C = 9.3|Oct low C = 2.1|Nov low C = -4.3|Dec low C = -12.1|precipitation colour = green|Jan precipitation mm = 63.2|Feb precipitation mm = 44.5|Mar precipitation mm = 70.2|Apr precipitation mm = 90.8|May precipitation mm = 105.7|Jun precipitation mm = 84.4|Jul precipitation mm = 103.2|Aug precipitation mm = 160.0|Sep precipitation mm = 165.7|Oct precipitation mm = 137.8|Nov precipitation mm = 85.2|Dec precipitation mm = 87.4|year precipitation mm = 1197.9|unit precipitation days = 1.0 mm|Jan precipitation days = 10.2|Feb precipitation days = 8.9|Mar precipitation days = 11.5|Apr precipitation days = 11.3|May precipitation days = 11.0|Jun precipitation days = 10.1|Jul precipitation days = 10.4|Aug precipitation days = 11.4|Sep precipitation days = 12.0|Oct precipitation days = 10.5|Nov precipitation days = 9.8|Dec precipitation days = 9.8|Jan snow cm = 132|Feb snow cm = 96|Mar snow cm = 105|Apr snow cm = 54|May snow cm = 3|Jun snow cm = 0|Jul snow cm = 0|Aug snow cm = 0|Sep snow cm = 0|Oct snow cm = 1|Nov snow cm = 31|Dec snow cm = 123|year snow cm = 548|unit snow days = 3 cm|Jan snow days = 12.3|Feb snow days = 10.4|Mar snow days = 12.1|Apr snow days = 7.0|May snow days = 0.4|Jun snow days = 0|Jul snow days = 0|Aug snow days = 0|Sep snow days = 0|Oct snow days = 0.1|Nov snow days = 3.9|Dec snow days = 13.0|Jan sun = 97.5|Feb sun = 111.9|Mar sun = 137.1|Apr sun = 154.0|May sun = 169.4|Jun sun = 146.3|Jul sun = 132.2|Aug sun = 115.7|Sep sun = 110.1|Oct sun = 123.3|Nov sun = 110.6|Dec sun = 107.3|year sun = 1546.0|source 1 = Japan Meteorological AgencyWEB,www.data.jma.go.jp/obd/stats/etrn/view/rank_a.php?prec_no=19&block_no=0091&year=&month=&day=&view=h0, ja:観測史上1～10位の値（年間を通じての値）Japan Meteorological Agency>JMA, March 3, 2022, WEB,www.data.jma.go.jp/obd/stats/etrn/view/nml_amd_ym.php?prec_no=19&block_no=0091&year=&month=&day=&view=h0, ja:気象庁 / 平年値（年・月ごとの値） Japan Meteorological Agency>JMA, March 3, 2022, }}

Gallery

File:Akan Caldera Relief Map, SRTM.jpg|Akan CalderaLake Akan (center)Mount Meakan (bottom left)Mount Oakan (center right)File:Lake Akan Kushiro Hokkaido Japan05n.jpg|Lake Akan and Mount OakanFile:Lake Akan - 2021 12 9.webm|A few scenes in 2021

See also

• List of Special Places of Scenic Beauty, Special Historic Sites and Special Natural Monuments
• Ramsar sites in Japan

References

{{reflist}}{{Commons category|Lake Akan}}{{Authority control}}