Estuary_of_St._Lawrence

Estuary of St. Lawrence

Estuary of St. Lawrence

Body of water at the mouth of the St. Lawrence river, in Quebec, Canada

For homonymy, see Saint Lawrence.

St. Lawrence Estuary stretches from west to east for 655 km, from the outlet of Lake Saint Pierre to pointe des Monts,[1] where it becomes the Gulf of St. Lawrence, in Quebec, Canada.

Quick Facts St. Lawrence Estuary Estuaire du Saint-Laurent (in French), Etymology ...

The estuary is divided into 3 parts, the fluvial estuary, the middle estuary and the maritime estuary.[1][2] The waters coming from the north shore of the St. Lawrence and Labrador come mainly from the Canadian Shield.[3]

Among the deepest and largest estuaries in the world, the St. Lawrence maritime estuary extends nearly 250 km before it widens at Point-des-Monts into the Gulf of St. Lawrence. This enclosed sea is connected to the Atlantic Ocean by Cabot Strait and the Strait of Belle-Isle.

Main articles: St. Lawrence River and Gulf of St. Lawrence
Birch bark canoe, Ilnu Museum in Mashteuiatsh,[4] Saguenay–Lac-Saint-Jean

The culture of the First Nations of Quebec, Canada and North America was largely based on birch. The birch bark canoe was a true work of art that provided these hunting peoples with the mobility essential to this way of life.[5][6]

After crossing the Gulf of St. Lawrence, the itinerary of the first Europeans: whalers, fishermen, explorers and navigators enters the waters of the Estuary, where the most difficult manoeuvres of the voyage begin: reefs, shoals, diagonal currents, fog and the presence of shallow channels, often narrow and winding, not to mention winter and ice and its unpredictable and fearsome storms. Throughout its history, the estuary or St. Lawrence River is not easily domesticated.[7]

Fluvial estuary

Lake Saint-Pierre, lighthouse, shoreline, Pointe-du-Lac

Running for about 160 km, the fluvial estuary or estuarine section of the river extends from the outlet of lake Saint-Pierre[8][9] to the RCM L'Islet; the portion of the river under the power of freshwater tides.

The average depth of the main channel varies from 13 to 40 m, with pools of 21 m in Trois-Rivières-Ouest and 60 m in Quebec City.[2]

Starting with lake Saint-Pierre, the ecological conditions of the St. Lawrence underwent a radical change. The slow and continuous advance of the great mass of fresh water gradually gives way to the regime of the upflow tide, where twice every twenty-four hours the shores undergo a short alternation of emersion and immersion.[10]

The waters of the streams and rivers that flow into the river differ from those of the St. Lawrence in terms of temperature, chemical composition and suspended solids. The main rivers of the fluvial estuary, on the south shore, are the Bécancour, Chaudière, Rivière du Sud rivers, on the north shore: St. Maurice Champlain, Batiscan, Sainte-Anne, Jacques-Cartier, Saint-Charles, Montmorency rivers and several secondary watercourses.

The waters retain their distinctiveness over a relatively long course before mixing. Those in the Rivière des Outaouais keep their properties up to 25 km downstream from the mouth of the Saint-Maurice. Downstream of Grondines, the currents of the rising tide (flood) reverse the direction of the river's flow. The result is an increasingly homogeneous stiring and mixing of fresh water from different sources.[2]

Flora

Extends along seven kilometres of shoreline in the St. Lawrence River’s fluvial estuary, the Grondines and Sainte-Anne-de-la-Pérade swamp is one of the last, large, treed swamps on the river.[11]

Between Saint-Augustin-de-Desmaures and Île aux Grues, from 2008 to 2012, three plants characteristic of the St. Lawrence freshwater estuary and in a precarious situation were monitored annually: Victorin's gentian (Gentianopsis virgata ssp. victorinii), Victorin's water-hemlock (Cicuta maculata var. victorinii) and Parker's Buckwheat (Eriocaulon parkeri).[12]

Middle estuary

Passage of couriers from Transat Quebec Saint-Malo[13], Saint-Laurent-de-l'Île-d'Orléans 2000

Running for about 195 km, the middle estuary of the St. Lawrence extends, according to the authors, from the eastern tip of Île d'Orléans[14] or Saint-Jean-Port-Joli, to the mouth of the Saguenay River. This estuary section widens rapidly from a few kilometres to 10 km, then to 20 km upstream of Île aux Coudres and the archipelago of L'Isle-aux-Grues.[2]

The middle estuary is mainly characterized by the mixing of freshwater-influenced waters with salt water and high turbidity (turbid water). The hydrodynamic conditions, mainly the reversal of tidal currents and the increase in the salinity gradient, are such that a large amount of suspended solids is trapped and forms a muddy plug (turbidity zone). At ebb tide, the average water flow reaches 90,000 m3/s (fresh and salt water) in Montmagny.[2]

Geomorphology

Over the millennia, several geomorphological events have shaped the landscape of the territory on the south shore of the middle estuary.

The tectonic movements responsible for the genesis of the Appalachian Mountains explain the nature and configuration of the bedrock. Ice and interglacial periods led to glaciations, melts, and marine invasions, ice movements level the Appalachian Mountains. The large layers of sediment in the territory are the legacy of tectonic movements combined whit glacial and interglacial periods.[15]

Maritime estuary

Saguenay–St. Lawrence Marine Park, Maritime estuary of St. Lawrence River, Tadoussac

Among the deepest and largest estuaries in the world, running for about 300 km, the maritime Estuary of the St. Lawrence extend, from the mouth of Saguenay River at Tadoussac to Pointe-des-Monts were begin the Gulf.

The two bodies of water that mix off the coast of Tadoussac give the Maritime Estuary characteristics that distinguish it from other reaches of the St. Lawrence: nutrient-rich surface waters throughout the summer and upwellings of deep, cold water that favour the formation of Euphausiids. -Krill beds exploited by large Baleen whales[17] It is home to the southernmost Beluga whale population in the world.[18][19]

This enclosed sea is connected to the Atlantic Ocean by Cabot Strait and the Strait of Belle-Isle.[20]

Fauna and flora

Habitats

The zone of contact between fresh and salt water corresponds to a region of high concentrations of suspended matter causing a zone of maximum turbidity (MTZ) of a length that can vary from 70 to 120 kilometres (43 to 75 mi), depending on the flow of the river.[21] This zone of maximum turbidity is located between Île d'Orléans (salinity greater than 0 PSU) and Île aux Coudres (salinity below 10 PSU). The mechanisms of estuarine circulation associated with this environment make it a privileged site of primary and secondary production which shelters many fish nurseries. High environmental turbidity provides shelter against predators while larvae are maintained under optimum temperature and salinity conditions.[22][23][24] Large variations in salinity and turbidity result in a wide variety of physicochemical conditions and planktonic communities on the river.

An emblematic species is the beluga (beluga whale), but many other species are present. An identification guide for marine fishes of the estuary and northern Gulf of St. Lawrence was completed in 2008.[25]

See also

References

  1. [1]
    "Pointe des Monts". Toponymy Quebec Commission (in French). Government of Quebec. 1968-12-05. Retrieved 20 February 2024. The coastline of Pointe des Monts on the North Shore and the city of Matane, opposite, in the Gaspé Peninsula, are the points that serve as the boundary between the estuary of the St. Lawrence River upstream, and the much wider Gulf of St. Lawrence, downstream.
  2. [2]
    "A river, estuaries, a gulf, the great hydrographic divisions" (PDF). Atlas of the St. Lawrence (in French). Atlas environnemental du Saint-Laurent. 1991. Retrieved 11 April 2024. The width of the Lower Estuary varies from 24 km to Tadoussac 50 km to Pointe-des-Monts
  3. [3]
    Historica Canada (2024). "Great Lakes-St. Lawrence Watershed" (in English and French). Canadian Encyclopedia. Retrieved 18 April 2024. The one million square kilometre region includes the Canadian portion of the watersheds of rivers that flow into the St. Lawrence River from east of Montreal, into the Gulf of St. Lawrence and into the Atlantic Ocean.
  4. [4]
    "Amerindian Museum of Mashteuiat". 2024. Retrieved 21 April 2024. Our team is composed of members from the Pekuakamiulnuatsh First Nation
  5. [5]
    Frère Marie-Victorin (1935). "The birch bark canoe, an exceptional reign". florelaurentienne.com (in French). florelaurentienne.com. pp. 150 of 925. Retrieved 21 April 2024. Betula papyrifera Marshall. — Bouleau à papier. — Bouleau blanc, Bouleau à canot. — (Canoë birch).
  6. [6]
    "Bark Canoe Construction". Canadian Museum of History. Government of Canada. Retrieved 21 April 2024. In Canada, the most popular bark for canoe construction has come from the paper birch
  7. [7]
    Alain Franck (2000-11-02). "Navigation on the St. Lawrence River" (PDF). La Fédération des sociétés d'histoire du Québec, 2000 (in French). Histoire Québec. p. 6. Retrieved 19 April 2024. The river, which the Amerindians had called "the walking way," was the only communication and transportation route for the pioneers.
  8. [8]
    "0303-carte.jpg". Sustainable development, Environment and Park. Retrieved 27 November 2008.
  9. [9]
    Manon Couture (21 October 2010). "Portrait and diagnosis of the Orphan Basin Zone of southern Lake Saint-Pierre" (PDF) (in French). Organisme de concertation pour l’eau des bassins versants de la rivière Nicolet (Copernic). pp. 14 of 75. The effect of the tides is faintly perceptible in Lake Saint-Pierre, the last freshwater basin before the estuary
  10. [10]
    Frère Marie-Victorin (1935). "St. Lawrence Estuarine Section". florelaurentienne.com (in French). pp. 53, 54. Retrieved 12 April 2024. The estuarine section is the portion of the river under the power of freshwater tides
  11. [11]
    "The Grondines and Sainte-Anne-de-la-Pérade Swamp". Nature Conservancy of Canada. Retrieved 18 April 2024. The diversity and number of birds that frequent the area's agricultural, forest and coastal lands are impressive — more than 100 bird species have been recorded in the area.
  12. [12]
    Hélène Gilbert (2013). "Monitoring of 3 rare plants from the St. Lawrence freshwater estuary" (PDF). Le Naturaliste canadien (in French). La Société Provancher d'histoire naturelle du Canada. p. 10. Retrieved 14 April 2024. Monitoring was carried out between Saint-Augustin-de-Desmaures and Île aux Grues, at 10 sites where at least one of these taxa was present.
  13. [13]
    Kate Jennings (19 July 2008). "A four part course between Quebec and Saint Malo". Sail-World. Retrieved 22 April 2024. The immense Saint Lawrence estuary emerges on the second part of the course, a veritable anti-chamber prior to the open ocean and the Atlantic.
  14. [14]
    Jean Poirier (1962). "The toponymy of Île d'Orléans" (PDF). Erudy (in English and French). Cahiers de géographie du Québec. pp. 2 of 19. Retrieved 21 April 2024. Île d'Orléans is located in the upper estuary of the St. Lawrence River, three miles downstream from the city of Quebec
  15. [15]
    "A coastal landscape with history!" (PDF). Conseil du Saint-Laurent (in French). Regional Consultation Table (TCR) of the South of the Middle Estuary. 2019-01-17. pp. 3 of 11. Retrieved 16 April 2024. Study several geomorphological events have shaped the landscape of the territory
  16. [16]
    "Baie de I'isle-verte National Wildlife Area" (PDF). Gouvernement of Canada. Environment and Climate Change Canada. 2021-07-07. Retrieved 25 April 2024. comprises 322 hectares in the form of a 20-kilometre strip along the south shore of the St. Lawrence Estuary, in the municipality of L'Isle-Verte, Quebec
  17. [17]
    "Whales of the St. Lawrence river". Whales Online. 2024. Retrieved 18 April 2024. The estuary is home to belugas all year round. In summer, the estuary also hosts rorquals and other species of toothed whales that benefit from the abundance of krill, capelin and other small fish.
  18. [18]
    "The Beluga Whale" (PDF). Fisheries and Oceans Canada. 2010-03-21. Retrieved 18 April 2024. The beluga whale frequents different habitats depending on the season and progression of ice breakup and freeze.
  19. [19]
    "Saguenay–St Lawrence Marine Park Management Plan 2010". Government of Canada. 2020-12-09. Retrieved 18 April 2024. The abundance of food in the Marine Park's ecosystems attracts many species of birds, whales and seals.
  20. [20]
    "The Estuary and the Gulf of St. Lawrence". Fischeries and Oceans Canada. Government of Canada. 2023-08-01. Retrieved 25 April 2024. Among the deepest and largest estuaries in the world
  21. [21]
    Silverberg, Norman; Sundby, Bjørn (1979-04-01). "Observations in the turbidity maximum of the St. Lawrence Estuary". Canadian Journal of Earth Sciences. 16 (4): 939–950. doi:10.1139/e79-080. ISSN 0008-4077.
  22. [22]
    Sirois, P; Dodson, Jj (2000). "Critical periods and growth-dependent survival of larvae of an estuarine fish, the rainbow smelt Osmerus mordax". Marine Ecology Progress Series. 203: 233–245. doi:10.3354/meps203233. ISSN 0171-8630.
  23. [23]
    North, E. W.; Houde, E. D. (October 2001). "Retention of White Perch and Striped Bass Larvae: Biological-Physical Interactions in Chesapeake Bay Estuarine Turbidity Maximum". Estuaries. 24 (5): 756. doi:10.2307/1352883. JSTOR 1352883. S2CID 32886478.
  24. [24]
    Winkler, G; Dodson, Jj; Bertrand, N; Thivierge, D; Vincent, Wf (2003). "Trophic coupling across the St. Lawrence River estuarine transition zone". Marine Ecology Progress Series. 251: 59–73. doi:10.3354/meps251059. ISSN 0171-8630.
  25. [25]
    C. Nozères; D. Archambault; P.-M. Chouinard; J. Gauthier; R. Miller; E. Parent; P. Schwab; L. Savard; J.-D. Dutil (2010). "Identification guide for marine fishes of the estuary and northern Gulf of St. Lawrence and sampling protocols used during trawl surveys between 2004 and 2008" (PDF) (in English and French). Regional Science Branch Fisheries and Oceans Canada, Maurice Lamontagne Institute. Retrieved 8 April 2024. Important source of information on the status of marine resources harvested in the estuary and northern Gulf of St. Lawrence.
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