Wikipedia

Estuary of St. Lawrence

(Redirected from Saint Lawrence estuary)
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.

St. Lawrence Estuary
Estuaire du Saint-Laurent (in French)
Maritime section at Port-au-Saumon
Estuary of St. Lawrence is located in Quebec
Estuary of St. Lawrence
Estuary of St. Lawrence is located in Canada
Estuary of St. Lawrence
EtymologySaint Lawrence of Rome
Location
CountryCanada
ProvinceQuebec
Physical characteristics
SourceSaint Lawrence River
 • locationLake Saint-Pierre, Trois-Rivières
 • coordinates46°16′17″N 72°38′5″W / 46.27139°N 72.63472°W / 46.27139; -72.63472
MouthGulf of St. Lawrence / Atlantic Ocean
 • location
Pointe des Monts
 • coordinates
49°08′N 67°14′W / 49.133°N 67.233°W / 49.133; -67.233
 • elevation
0 m (0 ft)
Discharge 
 • locationbelow the Saint Lawrence River

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]

Main articles: St. Lawrence River and Gulf of St. Lawrence

Fluvial estuary edit

 
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[4][5] 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.[6]

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 edit

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.[7]

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).[8]

Middle estuary edit

 
Middle estuary, Halte des Piliers, Route 132, Saint-Jean-Port-Joli

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 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]

Geomorphology edit

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.[9]

Maritime estuary edit

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

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[10] It is home to the southernmost Beluga whale population in the world.[11][12]

Situation edit

The estuary of the St. Lawrence River is located downstream of the St. Lawrence River and upstream of the Gulf of St. Lawrence. It refers to the place where the fresh and salt waters mix between the river and the gulf. The St. Lawrence Estuary begins at Lake Saint-Pierre and ends at the widening of the shores at the Pointe des Monts on the Côte-Nord to the city of Matane, opposite, in the Gaspé Peninsula, the distance is only 52 km. These points serve as a boundary between the estuary of the river upstream and the much wider Gulf of St. Lawrence downstream.[13]

The estuary is divided into sections: the St. Lawrence River estuary at Île d'Orléans (Orleans Island), the middle estuary to the Saguenay River. At this point, the St. Lawrence is characterized by a saline front at the eastern tip of Île d'Orléans.

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.[14] 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.[15][16][17] Large variations in salinity and turbidity result in a wide variety of physicochemical conditions and planktonic communities on the river.

Fauna and flora edit

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.[18]

See also edit

References edit

  1. ^ a b "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. ^ a b c d "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. ^ Historica Canada (2024). "Great Lakes-St. Lawrence Watershed" (in en and fr). 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.{{cite web}}: CS1 maint: unrecognized language (link)
  4. ^ "0303-carte.jpg". Sustainable development, Environment and Park. Retrieved 27 November 2008.
  5. ^ 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
  6. ^ 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
  7. ^ "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.
  8. ^ 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.
  9. ^ "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
  10. ^ "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.
  11. ^ "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.
  12. ^ "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.
  13. ^ "Pointe des Monts". Commission de toponymie Quebec. Gouvernement of Quebec. 1968-12-05. Retrieved 8 April 2024. The Pointe des Monts on the North Shore, at the city of Matane, opposite, in the Gaspé Peninsula, are the points that serve as the boundary between the estuary of the river and the Gulf of St. Lawrence
  14. ^ 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.
  15. ^ 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.
  16. ^ 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.
  17. ^ 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.
  18. ^ 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.

External links edit

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