is a

meromictic lake A meromictic lake is a lake which has layers of water that do not intermix. In ordinary, holomictic lakes, at least once each year, there is a physical mixing of the surface and the deep waters. The term ''meromictic'' was coined by the Austri ...

Abashiri is a city located in Okhotsk Subprefecture, Hokkaido, Japan. Abashiri is known as the site of the Abashiri Prison, a Meiji-era facility used for the incarceration of political prisoners. The old prison has been turned into a museum, but the city ...

Hokkaidō is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The la ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. It is located in

Abashiri Quasi-National Park is a quasi-national park in Japan.List of Quasi-National Parks
''Ministry o ...

. The

and Memanbetsu Rivers flow into the lake. Water exits the lake through the Abashiri River again and flows to the

Sea of Okhotsk The Sea of Okhotsk ( rus, Охо́тское мо́ре, Ohótskoye móre ; ja, オホーツク海, Ohōtsuku-kai) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands ...

History and formation

From core samples taken from the lake bed, the lake basin appears to have first formed some 20,000 years ago during the last period of glaciation. During the last 6000 years, the Abashiri River carved out the lake bed. Artifacts from the

Jōmon period The is the time in Japanese history, traditionally dated between 6,000–300 BCE, during which Japan was inhabited by a diverse hunter-gatherer and early agriculturalist population united through a common Jōmon culture, which reached a c ...

have been found in the area around the Memanbetsu River. In modern times, the course of the Abashiri River has been straightened to provide for

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

resulting in a serious

siltation Siltation, is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or ...

problem for the lake.

Freezing and salinity

The lake freezes over from December to April with ice up to a meter thick. The reduced inflow of water during the winter season causes saltwater to flow upstream from the

and into the lake. This influx of saltwater has created a layer of saline water with 10,000 ppm of

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

, below the surface of the lake with a freshwater upper layer that makes up 46% of the volume of the lake.

Fauna

The wakasagi (''Hypomesus nipponensis'')Masaru, T. (1999)
Life history polymorphism and the population dynamics of wakasagi (''Hypomesus nipponensis'') in Lake Abashiri, Hokkaido, Japan.
''Scientific Reports of Hokkaido Fisheries Experimental Station'' 56 1-117. and

corbicula ''Corbicula'' is a genus of freshwater and brackish water clams, Aquatic animal, aquatic bivalve mollusks in the family Cyrenidae, the basket clams.Gofas, S. (2015). Cyrenidae Gray, 1847. In: MolluscaBase (2015). Accessed through: World Registe ...

(''Corbicula japonica'') are common in the lake.

References

{{DEFAULTSORT:Abashiri Lakes of Hokkaido