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 Austria ...

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 ...

Hokkaido is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. It is located in Abashiri Quasi-National Park. 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; Historically also known as , or as ; ) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands on the southeast, Japan's island of Hokkaido on the sou ...

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 In Japanese history, the is the time between , during which Japan was inhabited by the Jōmon people, a diverse hunter-gatherer and early agriculturalist population united by a common culture, which reached a considerable degree of sedentism an ...

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 of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

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 o ...

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; it has 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 between ...

, 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 bivalve mollusks in the family Cyrenidae, the basket clams.Gofas, S. (2015). Cyrenidae Gray, 1847. In: MolluscaBase (2015). Accessed through: World Register of Marine Sp ...

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

References

{{DEFAULTSORT:Abashiri Lakes of Hokkaido Okhotsk Subprefecture