Above- and below-ground macrophyte production in Scirpus tidal marshes of the St. Lawrence estuary, Quebec

1988 ◽  
Vol 66 (5) ◽  
pp. 955-962 ◽  
Author(s):  
Jean-François Giroux ◽  
Jean Bédard
Keyword(s):  
Standing Crop ◽  
River Estuary ◽  
Dry Mass ◽  
Tidal Marshes ◽  
Lawrence Estuary ◽  
Aboveground Production ◽  
History Of ◽  
Below Ground ◽  
South Shore ◽  
St Lawrence Estuary

Above- and below-ground standing crops as well as primary production of several macrophytes were estimated in Scirpus marshes along the south shore of the St. Lawrence River estuary in Quebec. Aboveground standing crop was measured by clipping vegetation, while belowground standing crop was estimated by soil coring. Seasonal variation of live and dead standing crops was first determined for different plant species. The root:shoot mass ratio was then examined and related to the life history of each species. Total aboveground production varied from 74 to 627 g ash-free dry mass∙m−2∙year−1 among different plant communities, whereas belowground production was lower, with estimates varying between 38 and 244 g∙m−2∙year−1. Production was lower along the St. Lawrence estuary than in other types of marshes located farther south.

Estimating above- and below-ground macrophyte production in Scirpus tidal marshes

1988 ◽  
Vol 66 (2) ◽  
pp. 368-374 ◽  
Author(s):  
Jean-François Giroux ◽  
Jean Bédard
Keyword(s):  
Standing Crop ◽  
Belowground Biomass ◽  
Tidal Marshes ◽  
Optimal Size ◽  
Lawrence Estuary ◽  
Plant Parts ◽  
Peak Standing Crop ◽  
Below Ground ◽  
The Difference ◽  
St Lawrence Estuary

Different methods to estimate primary production of Scirpus marshes of the St. Lawrence estuary were compared. Quadrats 25 × 25 cm and cores 10 cm in diameter were found to be the optimal size to sample above- and below-ground standing crops, respectively. Ash content for different plant parts of various species was measured to obtain more accurate estimates of organic matter. A series of allometric equations relating stem height and mass were developed to estimate aerial standing crop from permanent nondestructively sampled plots. This method, however, overestimated standing crop compared with the destructive (harvest) method. The relationship between the above- and below-ground standing crop was also determined for the dominant species and used to predict belowground biomass without destructive sampling. Finally, the Smalley method provided the best estimates of net annual above- and below-ground production when losses attributed to decomposition were not considered. For less intensive studies, however, the methods based on peak standing crop and on the difference between maximum and minimum biomass would yield good approximations of above- and below-ground production.

The Saguenay Fjord: A Third Factor in the Toxic Chemical Contamination of the St. Lawrence River Estuary

1990 ◽  
Vol 25 (1) ◽  
pp. 1-14
Author(s):  
R.J. Allan
Keyword(s):  
Toxic Metals ◽  
River Estuary ◽  
Organic Chemical ◽  
Organic Chemicals ◽  
Chemical Contamination ◽  
Lawrence Estuary ◽  
The Past ◽  
Saguenay Fjord ◽  
St Lawrence Estuary ◽  
St Lawrence River

Abstract The Saguenay Fjord enters the north shore of the St. Lawrence River estuary. The St. Lawrence River is one source of a variety of toxic metals and organic chemicals to its estuary. Some of these chemicals are transported by the river from its source in Lake Ontario and others are added along its course. However, the second major source of water inflow to the St. Lawrence Estuary is the Saguenay Fjord, which is by no means free of contamination. This paper overviews the types of toxic metals and organic chemical contamination and sources in the fjord proper and upstream in its drainage basin. The principal contaminants recorded in bottom sediments are polyaromatic hydrocarbons and mercury. An extensive forest products industry may also be a source of toxic chlorinated organic chemicals. The combined (peak) inputs of these chemicals to the Saguenay Fjord system was in the past and may have continued for many years, even decades. The relationship between the type of contaminants introduced in the past to the St. Lawrence estuary by the St. Lawrence River and the Saguenay Fjord may have implications concerning contamination of the beluga whale population which is located most frequently in the estuary near the fjord inflow.

scholarly journals La mer de Goldthwait au Québec

2010 ◽  
Vol 31 (1-2) ◽  
pp. 61-80 ◽  
Author(s):  
Jean-Claude Dionne
Keyword(s):  
Quebec City ◽  
The South ◽  
Lawrence Estuary ◽  
Marine Invasion ◽  
North Shore ◽  
The North ◽  
Upper Limit ◽  
South Shore ◽  
Anticosti Island ◽  
St Lawrence Estuary

The Goldthwait Sea is defined as the late- and post-Glacial marine invasion in the St. Lawrence Estuary and Gulf east of Québec City. In Québec, this sea has submerged an area of about 25 000 km2. The largest areas submerged are the north shore of the St. Lawrence between Les Escoumins and Blanc-Sablon, the south shore between Levis and Tourelles, and the Anticosti Island. The upper limit of the Goldthwait Sea varies from place to place. The Goldthwait Sea began 14 000 years ago and land emergence is still in progress, since the pre-Wisconsin marine level has not been recovered yet. For a better chronology, this long interval needs to be subdivided. Three main periods have been recognized: Goldthwaitian I, II and III. However, a geographical subdivision is also needed. Numerous shorelines were observed at various elevations throughout the area formely submerged by the Goldthwait Sea. However, only a few shorelines are well developed and extensive, and correlations between former shorelines are difficult to establish. Only three levels are widespead and common to the Estuary and parts of the Gulf. The isostatic recovery has been rapid during the first three thousand years after déglaciation of the area: about 75%.

The food and feeding of common eiders in the St. Lawrence estuary in summer

1974 ◽  
Vol 52 (3) ◽  
pp. 319-334 ◽  
Author(s):  
M. Cantin ◽  
J. Bédard ◽  
H. Milne
Keyword(s):  
Intertidal Zone ◽  
Maximum Growth ◽  
Somateria Mollissima ◽  
Lawrence Estuary ◽  
Common Eiders ◽  
Feeding Activities ◽  
Food And Feeding ◽  
South Shore ◽  
Natural Foods ◽  
St Lawrence Estuary

The study was conducted in the St. Lawrence estuary during 1969 and 1970. The food abundance in the intertidal zone was measured in four Sampling stations located on the south shore of the river; the measurements revealed that over 95% of the available food of the common eider (Somateria mollissima) consisted of Littorina spp., Mytilus edulis, and Gammarus oceanicus. Both adult and young birds showed a distinct rhythm of feeding activities associated with tidal level. During the prenesting period, herring eggs and Nereis virens made up most of the food of adult common eiders. When accompanying ducklings, females ate mostly Littorina spp. and amphipods. Littorina spp. made up between 30 and 97% of the diet of the ducklings, the importance of this gastropod growing with age of the bird. Energy requirements during maximum growth were evaluated at about 460 kcal/bird per day on ducklings (age 54 days) fed natural foods, while between week 3 and week 8 it stood at about 520 kcal/bird per day in ducklings fed "turkey starter." These figures were used to assess the importance of the food removed by the eiders from the intertidal zone during the summer. We conclude that between 10 and 30% (according to the area) of the standing-crop biomass of Littorina alone (in July) is removed by the ducklings and the females accompanying them. At various moments through the season, these birds remove between 40 and 100 metric tons of mollusks per day from the intertidal zone.

scholarly journals TIDAL SEDIMENTATION IN GROS-CACOUNA HARBOR

1978 ◽  
Vol 1 (16) ◽  
pp. 120 ◽  
Author(s):  
Georges Drapeau ◽  
Guy Fortin
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediments ◽  
Suspended Sediment Transport ◽  
Lawrence Estuary ◽  
Seismic Profiling ◽  
Reflection Seismic ◽  
High Turbidity ◽  
South Shore ◽  
Bottom Sampling ◽  
St Lawrence Estuary

The harbor of Gros-Cacouna on the South shore of the St. Lawrence Estuary has been silting at the rate of 31 cm/yr. since it was dredged at the depth of 14 meters in 1968. Measurements of temperature, salinity, turbidity, current speed and direction were carried out as well as bottom sampling and reflection seismic profiling. A model of suspended sediment transport combines the tidal volumes and the current profiles at the harbor entrance. During a period of high turbidity (Spring) in the St.Lawrence Estuary, 54.2 tons of suspended sediments entered the harbor during the flood phase, while 41.1 tons were carried out during the ebb phase of a semi-diurnal tide, leaving 13.1 tons of sediments in the harbor. The transfer coefficient is 0.24 indicating that one quarter of the suspended sediment load settles in the harbor during one tidal cycle. In September, the turbidity is low in the Estuary and the suspended sediment budget in the harbor is 4 times smaller but the ratio of deposited sediments versus the total quantity of sediments transported in suspension is the same.

Hunting for Quaternary Faults in Eastern Canada: A Critical Appraisal of Two Potential Candidates

2020 ◽  
Author(s):  
Nicolas Pinet ◽  
Maurice Lamontagne ◽  
Mathieu J. Duchesne ◽  
Virginia I. Brake
Keyword(s):  
River Estuary ◽  
Seismic Profile ◽  
Fault Scarp ◽  
Seismic Zone ◽  
Eastern Canada ◽  
Lawrence Estuary ◽  
Surface Ruptures ◽  
St Lawrence Estuary ◽  
Fault Scarps ◽  
St Lawrence River

Abstract This study documents two potential neotectonic features in the seismically active St. Lawrence estuary and western part of the Gulf of St. Lawrence of Quebec, Canada. Historically, the region is the locus of series of damaging earthquakes, including the 1663 M 7 earthquake, which suggests the occurrence of coseismic surface ruptures beneath the St. Lawrence River. In the western Gulf of St. Lawrence (Lower St. Lawrence seismic zone), a potential fault scarp identified on a vintage seismic profile has been investigated through high-resolution seismic and multibeam bathymetry data. On the seafloor, the scarp corresponds to an ∼1.8  m high (maximum) feature that is located above a buried escarpment of the Paleozoic bedrock. Holocene units are draping over the escarpment on one profile, but are possibly cut on two others. The scarp meets several of the criteria generally associated with neotectonic features. However, a close look at the data indicates that the staircase geometry of the top of the bedrock and its expression at the surface is linked, at least partially, with the presence of an erosion-resistant unit. This makes a neotectonic reactivation possible but not proven. In the Tadoussac area, ∼40  km north of the Charlevoix seismic zone, the offshore extension of the St. Laurent fault corresponds to an ∼110  m high bathymetric escarpment with well-preserved triangular facets. Such “fresh” morphology is unique in the St. Lawrence River Estuary and may attest to Quaternary displacements, yet other interpretations may also explain the unusual preservation of the escarpment. These two case studies illustrate the difficulty to unambiguously document Holocene fault scarps, even in the marine domain in which the sedimentary succession is generally continuous.

Factors influencing aboveground production of Scirpus marshes in the St. Lawrence estuary, Québec, Canada

1987 ◽  
Vol 29 (3) ◽  
pp. 195-204 ◽  
Author(s):  
Jean-François Giroux ◽  
Jean Bédard
Keyword(s):  
Lawrence Estuary ◽  
Factors Influencing ◽  
Aboveground Production ◽  
St Lawrence Estuary

scholarly journals Densité agricole et charge humaine des terroirs : Essai méthodologique avec application à quatre comtés au sud de l’estuaire du Saint-Laurent

2005 ◽  
Vol 9 (17) ◽  
pp. 11-23
Author(s):  
Jean Raveneau
Keyword(s):  
Physical Environment ◽  
Population Based ◽  
Population Pressure ◽  
Direct Proportion ◽  
Lawrence Estuary ◽  
Real Population ◽  
Two Factors ◽  
Part Time ◽  
South Shore ◽  
St Lawrence Estuary

The density of agricultural population based on cleared land does not necessarily express the real population pressure in a given agricultural region. Two factors can upset the significance of this measure of density : (1) differences in the intensity of exploitation within a single territory ; and (2), variations in the proportion of part-time farmers. The author bas developed an index of the pressure of population on the land by making various calculations for jour counties in Québec, on the south shore of the St. Lawrence estuary. He bas found that the population pressure on the land varies in nearly direct proportion to the agricultural density based on cleared land, in spite of the lack of uniformity of the physical environment in question. The author concludes that the agricultural density retains its validity for expressing the population pressure on the land.

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