Lake Athabasca

• Category: Inland Aquatic Biomes.
• Geographic Location: North America.
• Summary: Lake Athabasca is a large freshwater lake supporting many species of fish and several mammal and bird species on its shores. It has also drawn attention from humans due to considerable amounts of oil deposited in nearby tar sands.

Canada's Lake Athabasca lies in northeastern Alberta and northwestern Saskatchewan. The Athabasca River flows from Jasper National Park northward, where it meets two other large rivers at the Peace-Athabasca Delta on the western shore of the lake. The lake has a surface area of 3,010 square miles (7,800 square kilometers) and an estimated water volume of 49 cubic miles (204 cubic kilometers). Outflow is northward, through Great Slave Lake, then eventually joining the Mackenzie River and thereby the Arctic Ocean.

The area of land that collects water draining into the Athabasca River and Lake Athabasca is known as the Athabasca watershed; its extent of 100,000 square miles (260,000 square kilometers) can be subdivided into multiple regions such as Rocky Mountain forests, temperate grasslands, wetlands, boreal forests, taiga, and tundra. Together, these biomes support a diversity of terrestrial and freshwater ecosystems.

The lake itself is home to multiple aquatic species, including large fish such as lake trout, northern pike, and Arctic grayling. The rivers feeding the lake are rich with nutrients, supporting the baitfish that the larger fish feed on. The banks of the lake's tributaries support mixed-wood forests and other riparian vegetation, which draws in mammal and amphibian species and serves as a staging site for migratory birds.

The plant makeup of the Peace-Athabasca Delta was largely affected by the building of the hydroelectric Bennett Dam on the Peace River in the 1960s. Originally a marsh, the area experienced significant water loss after the dam was built, leading to the exposure of mud flats, which were quickly colonized by tundra-subarctic forest transition species such as spike rush, slough grass, common great bulrush, smartweed, sedges, reed grass, and willows. These are plants that are able to survive low water levels.

Invertebrates and Fish

The Peace-Athabasca Delta and the channels associated with it are important because they act as feeding, spawning, and nursing areas for fish in Lake Athabasca. The considerable phytoplankton and aquatic macrophyte communities in the lake serve as a food source for smaller fish and invertebrates. The lakes and channels contain large daphnids and copepods; notably, the copepod Diacyclops bicuspidatus thomasi acts as an intermediate host for the tapeworm species Triaenophorus crassus, which infects lake whitefish and cisco in Lake Athabasca.

The dominant zooplankton species in the benthic (deepwater) region of the lake is the amphipod Monoporeia affinis (formerly known as Pontoporeiea affinis), and fingernail clams; midge larvae and snails are also present. The standing stock of benthic invertebrates tends to be low, however, because many areas of the delta freeze to the bottom.

Lake Athabasca is home to many species of fish and supports commercial, domestic, and sport fishing industries. Many of the sport and commercial fish use the delta as a spawning and nursery area. The species found in the lake include cisco, Arctic grayling, longnose sucker, white sucker, lake chub, spottail shiner, ninespine stickleback, trout perch, yellow perch, burbot, and longnose dace.

Lake trout, lake whitefish, walleye, and northern pike populations support the domestic and commercial fisheries. The latter set of fish are largely omnivorous, mostly feeding on benthic plankton, aquatic insects, crustaceans, and other invertebrates in their juvenile stages; as they increase in size, they prey on smaller fish, frogs, small mammals, and small waterfowl. Fish such as northern pike that feed on small land mammals seek their prey at the edge of weed beds, where they can attack unsuspecting animals.

Birds and Land Animals

The riparian areas of the Athabasca region draw in the most bird and mammal species as the increased vegetation provides a more hospitable environment than the harsh climate and sandy, shallow soils of the surrounding areas. The Peace-Athabasca Delta terrain is the most important to birds because it is relatively undisturbed and is positioned on several of North America's major migratory flight paths, or flyways. Whistling swans, geese, and the endangered whooping crane all use it for breeding, staging, and molting, as well as for nesting.

Notably, the peregrine falcon, which became a threatened species because of organochlorine pesticide poisoning in the 1950s and 1960s, is known to nest in the region. Waterfowl, including mallard, common merganser, and the common loon, are also present along the lake's shores and in vegetation along adjoining rivers. All of these birds feed on small invertebrates, such as crustaceans, insects, and worms, but mergansers and loons also feed on small fish.

The delta region is also a habitat for mammals such as caribou, which feed mostly on lichens, and moose, which are drawn to areas of dense shrub or wetlands where vegetation is rich in nutrients. Several species of hares, voles, shrews, mice, and porcupine serve as important food sources for larger predators. Also present are muskrat, beaver, marten, and mink; the sale of their furs is an important industry for First Nations groups.

The muskrats, which are semi-aquatic rodents, thrive in perched basins (small lakes that are refilled only by flooding) in the delta, and their numbers have decreased as a result of the less frequent flooding in the area due to the building of the Bennett Dam. Importantly, the sedge and grass meadows of Wood Buffalo National Park, which surrounds the delta, is home to the world's largest herd of roaming wood buffalo, a threatened species. The wood buffalo are preyed upon by wolves, the dominant carnivore in the area, although black bears, wolverines, weasel, marten, and lynx are also present.

Human Incursions

The health of the lake and its surrounding lands has been threatened by the extraction of uranium and tar sands, a major source of oil, in nearby areas. At Fort McMurray, Alberta, south and west of Lake Athabasca, lie the Athabasca Tar Sands, the world's largest known deposit of crude bitumen. The oil sands are thought to contain over 1.75 trillion barrels of oil. Water from the Athabasca River must be diverted to extract crude oil from the tar sands, and there are grave concerns about the effects of toxicants, especially heavy metals, polycyclic aromatic hydrocarbons, and solvents released or required for extraction, on the ecological and human communities in the area.

The results of recent studies on the effects of heavy metal poisoning on fish have so far been inconclusive or conflicting. In 2012, First Nations fishermen and ecologists working upstream of the sands, however, reported an increase in tumors, disease, and deformity in river fish, including whitefish, sucker, burbot, and northern pike. A compromise in the safety of the fish in the area may not only have serious effects on the viability of the Lake Athabasca fishing industry but also on the larger organisms that feed on them.

The Lake Athabasca region has been exposed to previous chemical threats due to uranium mining; the basin is among the world's largest known uranium resources. The search for uranium in the area began in 1942 for military reasons, and the wartime ban on private prospecting was lifted in 1947, leading to the discovery of major deposits on the northern shore of Lake Athabasca. In the 1950s, the provincial government established Uranium City to house men working at nearby mines; when a major mining company officially encouraged its employees to live in the city, the population began to boom, eventually reaching numbers close to 10,000. With the Cold War came increasing public anxiety about nuclear power, and when uranium's value dropped and the mines were shut down in 1983, the city collapsed. Though most of the area's former inhabitants have left, fears of contamination in the lake due to mine tailings and infrastructure dislocation persist.

Global warming may affect the lake in various ways. In close proximity, mainly to the north, lie vast stretches of peatlands, a major carbon sink. As temperatures rise, portions of this carbon, in the form of methane, are known to gas out, engendering a positive feedback loop by increasing concentrations of this potent atmospheric greenhouse gas. Lake Athabasca is expected to receive greater precipitation as ambient atmospheric temperatures rise, and winters are likely to grow somewhat milder. Earlier spring snowpack melts upstream are projected to yield higher water levels in the lake at that time of year. However, studies are unclear on how average water levels will play out over the other seasons, as factors such as smaller snowpack, increased evaporation, and greater available inflow due to expanded deforestation for agricultural purposes must be taken into consideration. The situation remains dynamic and complex.

Bibliography

Athabasca Land Use Planning Interim Advisory Panel. "Athabasca Land Use Plan." Government of Saskatchewan, 2003, www.environment.gov.sk.ca/Default.aspx?DN=77e08791-38ff-4b6c-bbd3-79c2af8320cc. Accessed 28 Oct. 2024.

"Climate Change in the Athabasca River Basin." Alberta Water Portal Society, 22 Feb. 2022, albertawater.com/climate-change-in-the-athabasca-basin/. Accessed 28 Oct. 2024.

Mitchell, P., and E. Prepas, editors. Atlas of Alberta Lakes. University of Alberta Press, 1990.

Piper, Liza. The Industrial Transformation of Subarctic Canada. University of British Columbia Press, 2009.

Schindler, D. W. "Sustaining Aquatic Ecosystems in Boreal Regions." Conservation Ecology, vol. 2, no. 2, 1998, pp. 18-36.

Tendler, Brett, et al. "Concentrations of Metals in Fishes from the Athabasca and Slave Rivers of Northern Canada." Environmental Toxicology and Chemistry, vol. 29, no. 11, Aug. 2020, doi.org/10.1002/etc.4852. Accessed 28 Oct. 2024.