Baykal Lake

Lake Baikal is a freshwater lake located in Eastern Siberia, notable for both its geological and biological significance. It is estimated to have formed approximately 25 to 30 million years ago and is considered one of the oldest lakes on Earth. With a maximum depth of 1,642 meters, it is the deepest lake in the world. It holds a water volume of 23,615 km³, containing the largest reserve of freshwater on the planet. Approximately 20–23% of the world’s unfrozen freshwater is found in Lake Baikal. With a surface area of 31,722 km², it ranks as the seventh largest lake in the world by surface area.

The lake is of great importance due to its biological diversity. Around 2,600 animal species and 1,000 plant species inhabit Lake Baikal, more than 80% of which are endemic, meaning they are found nowhere else on Earth. This characteristic makes Lake Baikal one of the most remarkable examples of a freshwater ecosystem. In 1996, the United Nations Educational, Scientific and Cultural Organization (UNESCO) designated Lake Baikal a World Heritage Site.

Geography

Lake Baikal is situated between the Irkutsk Oblast and the Republic of Buryatia in northeastern Central Asia. The lake lies at an elevation of 455.5 meters above sea level and measures 636 kilometers in length with a width ranging from 25 to 80 kilometers. Its shoreline extends for approximately 1,800 kilometers.

The lake lies atop the Baikal Rift System, an active tectonic rift zone where the Earth’s crust is expanding at a rate of about 4 millimeters per year. Earthquakes and hot springs occur along the fault lines within this system. The lake is divided into three main basins: Northern, Central, and Southern. The Academician Ridge and the Buguldeika Saddle form boundaries between these basins.

The lakebed is covered in places by sediment layers up to 7 kilometers thick, with the rift floor lying approximately 8–11 kilometers below the surface, forming the deepest continental depression on Earth. The lake is surrounded by mountains. The Baikal Mountains lie to the north, the Barguzin Range to the northeast, and the Primorsky Range to the west. There are 27 islands within the lake, the largest of which is Olkhon Island, measuring 72 kilometers in length and one of the largest lake islands in the world.

Lake Baikal is fed by more than 330 rivers, the main ones being the Selenga, Barguzin, Upper Angara, Turka, Sarma, and Snejnaya. The lake drains exclusively through the Angara River.

Water Properties (Hydrography)

Lake Baikal is one of the clearest freshwater lakes in the world. During winter months, water clarity in open areas can reach 30–40 meters, while in summer it typically ranges between 5 and 8 meters. The oxygen concentration in the water is very high, even at its deepest points. This distinguishes Lake Baikal from stratified lakes such as the Black Sea.

Surface temperature varies significantly throughout the year. The lake is ice-covered for 4–5 months during winter and early spring. Ice thickness generally ranges from 0.5 to 1.4 meters, reaching over 2 meters in some areas. During this period, surface water temperature is slightly below freezing, while at depths of 200–250 meters it remains at 3.5–3.8 °C. From May to June, as surface ice melts, the upper layers up to 300 meters reach a uniform temperature of approximately 4 °C (monomictic condition). During summer, surface temperatures can rise to 16 °C, and in shallow southern bays, up to 20–24 °C. Temperature decreases with depth during this season. In autumn, the surface cools again, and from October to November a second monomictic period occurs. Below 300 meters, the temperature remains constant year-round, varying between 3.1 and 3.4 °C.

Over the past 50 years, surface temperatures have increased by approximately 1.5 °C, and the duration of ice cover has shortened. Subsurface heat sources, with temperatures around 50 °C, do not significantly contribute to the lake’s overall temperature, but they have been observed in areas such as Frolikha Bay, Kukuisky Canyon, and the Selenga Delta.

Lake Baikal frequently experiences storms in summer and autumn, with wave heights reaching up to 4.5 meters.

Vegetation

The surrounding area and shoreline of Lake Baikal feature a highly diverse aquatic and semi-aquatic vegetation. Over 1,000 plant species have been identified. In wetlands and reed beds around the lake, Common Cattail (Cirsium palustre) is widespread. This species has historically dominated habitats of the Juncus subnodulosus/Cirsium palustre type, shaped by Holocene agricultural practices.

The ecological role of Common Cattail extends beyond vegetation, as it serves as a host for numerous pollinators and larvae. Its flowers are visited by more than 39 insect species, and the larvae of genera such as Cheilosia and Agapanthia feed on this plant.

Submerged macrophytes are primarily found in shallow bays. Genera such as Ceratophyllum, Myriophyllum, Potamogeton, and Sparganium have been recorded. Green algae (particularly Draparnaldioides, Tetraspora, and Ulothrix) and approximately 400 species of siliceous algae (diatoms) are common in the lake. Half of these diatom species are endemic.

Animal Community

Although fewer than 65 native fish species inhabit Lake Baikal, more than half are endemic. The golomyanka fish (Comephorus baicalensis and C. dybowskii), deepwater sculpins, and other bottom-dwelling fish unique to Baikal live nowhere else. Golomyanka fish inhabit depths of 100–500 meters and are the deepest-living freshwater fish in the world. They constitute the primary food source for the Baikal seal and form the largest fish biomass in the lake.

The omul (Coregonus migratorius) is a unique and commercially important fish of the lake. In addition, C. baicalensis, the Baikal sturgeon (Acipenser baerii baicalensis), and the Baikal black and white graylings (Thymallus baikalensis and T. brevipinnis) are also endemic.

The only mammal native to Lake Baikal is the Baikal seal (Pusa sibirica). It spends its entire life cycle in the lake and can dive to depths of up to 400 meters. Its population numbers between 80,000 and 100,000 individuals. It gives birth in dens dug into snow and ice, feeds on golomyanka fish, and uses its thick blubber layer and powerful front flippers to create breathing holes in the ice.

The most abundant animal in the lake is the copepod Epischura baicalensis, which makes up 80–90% of the zooplankton and is estimated to filter the entire volume of the lake once every 23 years. Amphipods, with over 350 species including Macrohectopus, Acanthogammarus, and Brachyuropus, show high diversity; some species grow up to 7 cm in length.

Among freshwater mollusks, nearly 150 snail species have been identified, 117 of which are endemic. More than 30 species of bivalve mollusks occur in the lake, half of which are unique to Baikal. There are approximately 200 species of oligochaete worms and over 140 endemic flatworm species. Eighteen sponge species are found in Lake Baikal; the most common are Lubomirskia baicalensis, Baykalospongia bacillifera, and B. intermedia.