Lake Baikal is a rift lake and the deepest lake in the world. It is situated in southern Siberia, Russia, between the federal subjects of Irkutsk Oblast to the northwest and the Republic of Buryatia to the southeast.
At —slightly larger than Belgium—Lake Baikal is the world's seventh-largest lake by surface area, as well as the second-largest lake in Eurasia after the Caspian Sea. However, because it is also the deepest lake, with a maximum depth of , Lake Baikal is the world's largest freshwater lake by volume, containing of water or 22–23% of the world's fresh surface water, more than all of the North American Great Lakes combined. It is also the world's oldest lake at 25–30 million years, and among the clearest. It is estimated that the lake contains around 19% of the unfrozen fresh water on the planet.
Lake Baikal is home to thousands of species of plants and animals, many of them endemic to the region. It is also home to Buryat tribes, who raise goats, camels, cattle, sheep, and horses, on the eastern side of the lake within Buryatia, where the mean temperature varies from a winter minimum of to a summer maximum of . The region to the east of Lake Baikal is referred to as Transbaikalia or as the Transbaikal, and the loosely defined region around the lake itself is sometimes known as Baikalia. UNESCO declared Baikal a World Heritage Site in 1996.
Geography and hydrography
Lake Baikal is in a rift valley, created by the Baikal Rift Zone, where the Earth's crust is slowly pulling apart. At long and wide, Lake Baikal has the largest surface area of any freshwater lake in Asia, at , and is the deepest lake in the world at . The surface of the lake is above sea level, while the bottom of the lake is below sea level, and below this lies some of sediment, placing the rift floor some below the surface, the deepest continental rift on Earth.
In geological terms, the rift is young and active—it widens about per year. The fault zone is also seismically active; hot springs occur in the area and notable earthquakes happen every few years. The lake is divided into three basins: North, Central, and South, with depths about , , and , respectively. Fault-controlled accommodation zones rising to depths of separate the basins. The North and Central basins are separated by Academician Ridge, while the area around the Selenga Delta and the Buguldeika Saddle separates the Central and South basins. The lake drains into the Angara, a tributary of the Yenisey. Landforms include Cape Ryty on Baikal's northwest coast.
Baikal's age is estimated at 25–30 million years, making it the most ancient lake in geological history. It is unique among large, high-latitude lakes, as its sediments have not been scoured by overriding continental ice sheets. Russian, U.S., and Japanese cooperative studies of deep-drilling core sediments in the 1990s provide a detailed record of climatic variation over the past 6.7 million years.
Longer and deeper sediment cores are expected in the near future. Lake Baikal is the only confined freshwater lake in which direct and indirect evidence of gas hydrates exists.
The lake is surrounded by mountains; the Baikal Mountains on the north shore, the Barguzin Range on the northeastern shore and the Primorsky Range stretching along the western shore. The mountains and the taiga are protected as a national park. It contains 27 islands; the largest, Olkhon, is long and is the third-largest lake-bound island in the world. The lake is fed by as many as 330 inflowing rivers. The main rivers draining directly into Baikal are the Selenga, the Barguzin, the Upper Angara, the Turka, the Sarma, and the Snezhnaya. It is drained through a single outlet, the Angara.
Regular winds exist in Baikal's rift valley.
Water characteristics
Baikal is one of the clearest lakes in the world. During the winter, the water transparency in open sections can be as much as , but during the summer it is typically .Freshwater Ecoregions of the World (2008). Lake Baikal. Retrieved 16 July 2014. Baikal is rich in oxygen, even in deep sections, which separates it from distinctly stratified bodies of water such as Lake Tanganyika and the Black Sea.
In Lake Baikal, the water temperature varies significantly depending on location, depth, and time of the year. During the winter and spring, the surface freezes for about 4–5 months; from early January to early May–June (latest in the north), the lake surface is covered in ice. On average, the ice reaches a thickness of , but in some places with hummocks, it can be more than . During this period, the temperature slowly increases with depth in the lake, being coldest near the ice-covered surface at around freezing, and reaching about at a depth of .
After the surface ice breaks up, the surface water is slowly warmed by the sun, and in May–June, the upper becomes homothermic (same temperature throughout) at around because of water mixing. The sun continues to heat up the surface layer, and at the peak in August can reach up to about in the main sections and in shallow bays in the southern half of the lake.
During this time, the pattern is inverted compared to the winter and spring, as the water temperature falls with increasing depth. As the autumn begins, the surface temperature falls again and a second homothermic period at around of the upper circa occurs in October–November. In the deepest parts of the lake, from about , the temperature is stable at with only minor annual variations.
The average surface temperature has risen by almost 1.5 °C (2.7 °F) in the last 50 years, resulting in a shorter period when the lake is covered by ice. At some locations, hydrothermal vents with water that is about have been found. These are mostly in deep water but locally have also been found in relatively shallow water. They have little effect on the lake's temperature because of its huge volume.
Stormy weather on the lake is common, especially during the summer and autumn, and can result in waves as high as .
Ecology
Lake Baikal is rich in biodiversity. It hosts more than 1,000 species of plants and 2,500 species of animals based on current knowledge, but the actual figures for both groups are believed to be significantly higher.
Flora The watershed of Lake Baikal has numerous floral species represented. The marsh thistle (Cirsium palustre) is found here at the eastern limit of its geographic range.C. Michael Hogan. 2009. Marsh Thistle: Cirsium palustre, GlobalTwitcher.com, ed. N. Strömberg
Submerged macrophytic vascular plants are mostly absent, except in some shallow bays along the shores of Lake Baikal. More than 85 species of submerged macrophytes have been recorded, including genera such as Ceratophyllum, Myriophyllum, Potamogeton, and Sparganium. The invasive species Elodea canadensis was introduced to the lake in the 1950s. Instead of vascular plants, aquatic flora is often dominated by several green algae species, notably Draparnaldioides, Tetraspora, and Ulothrix in water shallower than ; although Aegagrophila, Cladophora, and Draparnaldioides may occur deeper than . Except for Ulothrix, these green algae genera contain species endemic to Baikal. More than 400 diatom species, both benthic and planktonic, are found in the lake, and about half of these are endemic to Baikal; however, significant taxonomic uncertainties remain for this group.
Mammals
The Baikal seal or nerpa (Pusa sibirica) is endemic to Lake Baikal.Peter Saundry. 2010. Baikal seal. Encyclopedia of Earth. Topic ed. C. Michael Hogan, Ed. in chief C. NCSE, Washington D.C.
A wide range of land mammals can be found in the habitats around the lake, such as the brown bear (Ursus arctos), Eurasian wolf (Canis lupus lupus), red fox (Vulpes vulpes), sable (Martes zibellina), stoat (Mustela erminea), least weasel (Mustela nivalis), Eurasian otter (Lutra lutra), snow leopard (Panthera uncia), Siberian tiger (Panthera tigris tigris), Amur leopard (Panthera pardus orientalis), moose (Alces alces), elk (Cervus canadensis), reindeer (Rangifer tarandus), Siberian roe deer (Capreolus pygargus), Siberian musk deer (Moschus moschiferus), wild boar (Sus scrofa), red squirrel (Sciurus vulgaris), Siberian chipmunk (Eutamias sibiricus), marmots (Marmota sp.), lemmings (Lemmus sp.), and mountain hare (Lepus timidus). Until the Early Middle Ages, populations of the European bison (Bison bonasus) were found near the lake; this represented the easternmost range of the species.Sipko P.T.. 2009. European bison in Russia – past, present and future (pdf). the European Bison Conservation Newsletter Vol 2 (2009). pp.148–159. the Institute of Problems Ecology and Evolution RAS. Retrieved on 31 March 2017
Birds
There are 236 species of birds that inhabit Lake Baikal, 29 of which are waterfowl. Although named after the lake, both the Baikal teal and Baikal bush warbler are widespread in eastern Asia.
Fish
Fewer than 65 native fish species occur in the lake basin, but more than half of these are endemic.FishBase: Species in Lake Baikal. Retrieved 6 April 2017. The families Abyssocottidae (deep-water sculpins), Comephoridae (golomyankas or Baikal oilfish), and Cottocomephoridae (Baikal sculpins) are entirely restricted to the lake basin. All these are part of the Cottoidea and are typically less than long. Of particular note are the two species of golomyanka (Comephorus baicalensis and C. dybowskii). These long-finned, translucent fish typically live in open water at depths of , but occur both shallower and much deeper. Together with certain abyssocottid sculpins, they are the deepest living freshwater fish in the world, occurring near the bottom of Lake Baikal. The golomyankas are the primary prey of the Baikal seal and represent the largest fish biomass in the lake.Pastukhov, V.D: Lake Baikal Seals – NERPA. Retrieved 19 July 2014. Beyond members of Cottoidea, there are few endemic fish species in the lake basin.
The most important local species for fisheries is the omul (Coregonus migratorius), an endemic whitefish. It is caught, smoked, and then sold widely in markets around the lake. Also, a second endemic whitefish inhabits the lake, C. baicalensis. The Baikal black grayling (Thymallus baicalensis), Baikal white grayling (T. brevipinnis), and Baikal sturgeon (Acipenser baerii baicalensis) are other important species with commercial value. They are also endemic to the Lake Baikal basin.Baikal.ru: Baikal grayling. Retrieved 19 July 2014.Baikal.ru: Baikal sturgeon. Retrieved 19 July 2014.
Invertebrates The lake hosts a rich endemic fauna of invertebrates. Among the most diverse invertebrate groups are the amphipod and ostracod crustaceans, freshwater snails, annelid worms and turbellarian worms.
Crustaceans
More than 350 species and subspecies of amphipods are endemic to the lake. They are exceptionally diverse in ecology and appearance, ranging from the pelagic Macrohectopus to the relatively large deep-water Abyssogammarus and Garjajewia, the tiny herbivorous Micruropus, and the parasitic Pachyschesis (parasitizing other amphipods). The "gigantism" of some Baikal amphipods, which has been compared to that seen in Antarctic amphipods, has been linked to the high level of dissolved oxygen in the lake. Among the "giants" are several species of spiny Acanthogammarus and Brachyuropus (Acanthogammaridae) found at both shallow and deep depths. These conspicuous and common amphipods are essentially carnivores (will also take detritus), and can reach a body length up to . Another common species is another unique inhabitant of the lake: the pelagic amphipod Macrohectopus branickii lives its entire life in the water column, which is unique among freshwater amphipods and has been compared to krill.