Lena River ecosystem

• Category: Inland Aquatic Biomes.
• Geographic Location: Asia.
• Summary: This Siberian river is one of the largest in the world, and its delta supports an important habitat for migratory and nesting bird species.

The Lena River is located in eastern Russia. After the Ob River and the Yenisei River, it is the third-largest catchment area in Asia, at 926,645 square miles (2.4 million square kilometers). It originates in the Baikal Mountains, west of Lake Baikal in the Siberian Plateau, and discharges via a delta approximately 249 miles (400 kilometers) wide into the Laptev Sea and the Arctic Ocean. As a result of mixing river water in the Laptev Sea, there is a brackish surface plume of more than 217 miles (350 kilometers) over the saline seawater. The vast Lena River delta alone includes more than 6,000 watercourses, more than 50,000 lakes, and 1,600 islands.

The Lena River’s catchment area is predominantly underlain by 78–93 percent permafrost. More than 70 percent of the catchment area is covered by forests, of which more than 90 percent are needle-leaved deciduous forests comprised mainly of larch. In the delta area that is dominated by tundra, vegetation is sparser, and the regularly flooded areas with waterlogged soil are, if vegetated, covered by grassland or woody vegetation. Most of the overall catchment area is dominated by a continental climate, but a polar climate predominates toward the Arctic Ocean.

After winding some 2,800 miles (4,500 kilometers) from its source, the Lena makes a massive discharge into the Laptev Sea; its volume at the mouth is sufficient to make it one of the ten largest flows among major rivers of the world. The Lena River accounts for more than 70 percent of the total freshwater input to the Laptev Sea, and for about 19 percent of the input to the Arctic Ocean. The flow shows considerable seasonal differences, however, because the river is frozen for about eight months per year, from October through May.

The Lena River has three main tributaries: the Vilyuy, Aldan, and Vitim Rivers. The main channel of the Lena River is not much affected by flow regulation. Its tributary the Vilyuy has been saddled with several dams, and so has one minor tributary. In an international comparison, the effect of fragmentation and flow regulation in the Lena River is classified as moderate.

The permafrost in the catchment, both active-layer and upper-layer, is sensitive to temperature. Increases in air temperature affect snow depth and rainfall, and result in increased soil moisture. This alters the properties of the active permafrost layer and induces warming of the upper permafrost. In turn, this potentially affects the chemical properties of the river. In comparison with other major rivers of the world, the Lena is characterized by low concentrations of particulate material and by high concentrations of dissolved organic carbon—thus it has ecological service value as a significant carbon sink.

Biodiversity

The Lena River holds more than 35 fish species, of which several are important for sport and commercial fishing, including grayling (Thymllus spp.), sheefish (Stenodus leucichthys), burbot, chum salmon, sturgeon, nelma (Stenodus leucycthis), and Arctic cisco (Coregonus autumnalis). Some marine biologists consider the Lena River Delta to be the original cradle of the Arctic cisco, which is anadromous and is present in all marginal seas around the Arctic. The delta fish populations in general are potentially threatened by overfishing, especially as global warming begins to provide more time annually when waters here will be ice-free.

The Arctic lamprey (Lethenteron japonicum) is one of the more unusual species found in the Lena; an eel-like fish that feeds mainly on invertebrates and algae, it features two large teeth on its tongue.

The tundra in the delta area that is flooded each year is an important habitat for many migratory and nesting bird species; it is one of the richest Arctic areas for species diversity and breeding densities. A 1997 survey observed 16 mammal and 122 bird species in the delta. Of these bird species, including swans, geese, loons, ducks, gulls, terns, black brant, Steller’s eiders, plovers, sandpipers, and raptors, 67 bred at least once during the survey period.

The riparian zone and the banks of the Lena River host several endemic (found nowhere else) plant species. Endemic herbs include Redowskia sophiifolia of the magnolia clade, and Ceratoides lenensis, a tundra fescue. Dandelion, thought of as a weed in many parts of the world, grows abundantly along the Lena’s banks and is considered, along with other endemic herbs here, a medicinal plant.

Threats and Conservation

The Lena River catchment is sparsely populated; settlements and villages are mostly located along the riverbanks. Initially, the banks were inhabited by paleo-Asiatic tribes and later by the Sakha or Yakut people, whereas in modern times, Russians are most numerous. Subsistence fishing, farming, and hunting are still among the most significant activities of humans in much of the Lena River catchment.

Threats to this biome include pollution from mining, logging, and related industrial activities; agricultural runoff; and climate change. The Lena’s waters are considered some of the cleanest in the world. Keeping those waters clean for future generations is of prime consideration. Climate change impacts on the Lena River include changes in the water flow that feeds the Lena due to changes in temperature, evaporation, and precipitation. Research shows streamflow of the Lena increased by 22 percent from 1936 to 2019. This correlates to global climate change-related precipitation increase and permafrost thawing. Additionally, air temperature in the area has increased from 4.1 degrees Celsius from the period of 1950-1999 to 6.1 degrees Celsius during the first quarter of the 21st century.

In the Lena River Delta area, prevailing pollutants that have been detected include phenols, copper, oil products, and pesticides. The main pollutants are wastewater from industrial companies that are heavy water users, including mining and oil-producing enterprises. The pollution level of the Lena River is generally regarded to be low overall, however.

The Lena River is protected by three federal natural reserves. The Baikalo-Lensky Nature Reserve protects the headwater area; the Olyokminsky Nature Reserve protects the middle stream area; and the Ust-Lensky Nature Reserve protects the delta area. With its area of 23,552 square miles (61,000 square kilometers), the Ust-Lensky Nature Reserve, founded in 1986, is the largest nature reserve in Russia.

Bibliography

Chalov, Sergey; et. al. “Climate Change Impacts on Streamflow, Sediment Load and Carbon Fluxes in the Lena River Delta.” Ecological Indicators, vol. 157, 2023, doi.org/10.1016/j.ecolind.2023.111252. Accessed 11 Nov. 2024.

Dynesius, Mats and Christer Nilsson. “Fragmentation and Flow Regulation of River Systems in the Northern Third of the World.” Science 266, no. 4 (1994).

Gilg, Olivier, Raphaël Sané, Diana V. Solovieva, Vladimir I. Pozdnyakov, Brigitte Sabard, and Dmitri Tsanos, et al. “Birds and Mammals of the Lena Delta Nature Reserve, Siberia.” Arctic 53, no. 2 (2000).

Ijima, Yoshihiro, Alexander N. Fedorov, Hotaek Park, Kazuyoshi Suzuki, Hironori Yabuki, and Trofim C. Maximov, et al. “Abrupt Increases in Soil Temperatures Following Increased Precipitation in a Permafrost Region, Central Lena River Basin, Russia.” Permafrost and Periglacial Processes 21 (2010).

Nikanorov, A., V. Bryzgalo, L. Kosmenko, and O. Reshetnyak. “Anthropogenic Transformation of Aquatic Environment Composition in the Lena River Mouth Area.” Water Resources 38, no. 2 (2011).

Wang, Ping, et al. "Potential Role of Permafrost Thaw on Increasing Siberian River Discharge." Environmental Research Letters, vol. 16, no. 3, 2021, iopscience.iop.org/article/10.1088/1748-9326/abe326. Accessed 11 Nov. 2024.