Lake Onega

• Category: Inland Aquatic Biomes.
• Geographic Location: Northern Europe.
• Summary: The second-largest lake in Europe, surrounded by some of the region’s oldest coniferous forests, has relatively good water quality and fairly rich animal diversity.

Lake Onega is an inland lake situated in the Karelian region of northwestern Russia, close to the border of Finland and Eastern Europe. The second-largest lake in Europe, its surface area is approximately 3,700 square miles (9,700 square kilometers). The lake drains through the River Svir, which eventually empties into the Baltic Sea. Lake Onega is relatively deep, with an average depth of 98 feet (30 meters), with its deepest point being 417 feet (127 meters). There are more than 1,600 islands on the lake.

The lake is fed by about 50 tributaries; the three most important rivers flowing into Lake Onega are River Vodla, River Shuja, and River Suna; combined, they account for 60 percent of the riverine inflow. Lake Onega is connected to both the White Sea and Arctic Ocean, as well as the Baltic Sea through a network of canals—and to the Caspian Sea through the River Volga and its canal links. The human population around Lake Onega is about 300,000. The majority live in the vicinity of Petrozadovsk, the capital of Karelia, which in 2022 had an estimated population of 280,890.

Lake Onega is in the Atlantic continental climate zone. The average temperature in January is 18 degrees F (minus 8 degrees C), and the average temperature in July is 62 degrees F (16 degrees C). Average annual precipitation is 20–28 inches (50–70 centimeters).

Flora and Fauna

Lake Onega lies amidst the global coniferous forest belt, or boreal forest, that stretches from Canada to Siberia. In Russia, the forest is called the northern taiga. In these forests, northern and southern species meet, making them very biologically diverse. Human impact in the Karelian forests has remained minor. Consequently, these northwestern Russian forests are among the last remaining fairly pristine forests in Europe.

Lake Onega has interaction with numerous rivers where wild freshwater salmon spawn. Baltic salmon (Salmo salar) became landlocked in the Karelian lakes as a result of land uplift; they have been living in these lakes for about 130,000 years. In the twenty-first century, pollution and poaching threatened salmon populations; earlier, construction of dams and timber rafting were their main threats.

Lake Onega features a large variety of fish and aquatic invertebrates, including relics of the glacial period, such as lamprey. There are about 47 fish species from 13 families; they include: sturgeon, brown trout, European smelt, grayling, whitefish, char, pike, common dace, silver bream, carp, perch, spined loach, wels catfish, European eel, rudd, gudgeon, ruffe, and burbot.

Near Kizhi Island, one of the largest in the lake, about 180 bird species from 15 families have been identified; perhaps one-quarter of them were observed on the island itself. Most of these species are migratory and stop on the island either for rest or nesting, such as swans, geese, ducks, lake seagulls, and sterna—but there are also more stationary birds such as sparrow, siskin, chaffinch, skylark, jackdaw, and crow.

The banks of Lake Onega are low and often flooded; they are swampy and rich in reeds and other wetland vegetation, hosting ducks, geese, and swans. Mammals include elk, brown bear, wolf, fox, hare, squirrel, lynx, marten, and European badger, as well as American muskrat and mink, which were introduced to the area in the early 20th century.

Human Impact

The beauty of the lake and its islands attracts an increasing number of tourists, which bring with them some degree of ecological wear and tear. Kizhi Island, a United Nations Environmental, Scientific, and Cultural Organization (UNESCO) World Heritage site, is renowned for its natural beauty and bird species, and for the eighty-nine wooden churches—in particular, Kizhi Pogost, a settlement that features a summer 22-dome church, a winter nine-dome church, and a striking belfry. The oldest church on Kizhi dates from the 1300s.

On the whole, the water quality of Lake Onega is good, but the anthropogenic impact is intense around Petrozadovsk and the city of Kondopoga; both are situated in bays on the northwestern side of the lake. Biologically treated domestic sewage and raw industrial wastewater from these urban sites are discharged into Lake Onega. This has led to strong blooms of blue-green algae in Petrozadovsk Bay during the summer. The bay receives 1.6 times more total phosphorus and five times more total nitrogen than Kondopoga Bay, which is a deeper and larger bay.

The biggest polluter in Kondopoga Bay is a major paper pulp mill, one of the most important paper producers in Russia, and still in action after more than eighty years of service. After having discharged untreated sewage into Kondopoga Bay for more than fourty years, its sewage is being treated. In 2021, the company announced modernization plans.

Lake Onega’s water column layering helps combat nutrient pollution. Strong stratification in the water column prevents much mixing of water, and helps isolate the deeper, central part of the lake from the waters of the polluted bays. At any rate, since the 1990s, a diminishing nutrient and waste load in the catchment area has resulted in a decrease in levels of nitrogen and phosphorus in both Petrozadovsk and Kondopoga bays.

Climate change in the region has shown trends of milder winters with an increased number of thaw days, and wetter springs with significant amounts of precipitation. Changes in air temperature, precipitation, and other meteorological qualities can cause changes in water balance, lake level, thermal characteristics, and ice events, as well as hydrochemical and hydrobiological regimes across the lake ecosystem. What this means in terms of the response of the Onega Lake environment will depend on the future intensity of regional climate change.

Bibliography

Bilaletdin, Ä., et al. "A General Water Protection Plan of Lake Onega in Russia." Water Resource Management, vol. 25, 2011, pp. 973-95.

Malov, V. I., et al. "Distribution of Mercury Content in the System Water-Suspended Matter-Bottom Sediments of the Water Area of Lake Onega (NW Russia)." Limnology and Freshwater Biology, vol. 5, no. 3, 2022, doi.org/10.31951/2658-3518-2022-A-3-1245. Accessed 7 Nov. 2024.

Ozerov, M. Y., et al. "Genetic Structure of Freshwater Atlantic Salmon (Salmo salar L.) Populations from the Lakes Onega and Ladoga of Northwest Russia and Implications for Conservation." Conservation Genetics, vol. 11, 2010, pp. 1501-17.

Podsechin, Victor, et al. "Development of Water Protection of Lake Onega." The Finnish Environment, vol. 36, 2009, pp. 1-85.

Sabylina, A. V., et al. "Water Chemistry of Lake Onega and its Tributaries." Water Resources, vol. 37, 2010, pp. 544-59.