scholarly journals The Gulf of St. Lawrence Biogeochemical Model: A Modelling Tool for Fisheries and Ocean Management

2021 ◽  
Vol 8 ◽  
Author(s):  
Diane Lavoie ◽  
Nicolas Lambert ◽  
Michel Starr ◽  
Joël Chassé ◽  
Olivier Riche ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Dissolved Oxygen ◽  
Phytoplankton Bloom ◽  
Biogeochemical Model ◽  
Carbonate System ◽  
Lawrence Estuary ◽  
Ocean Management ◽  
System Components ◽  
St Lawrence Estuary

The goal of this paper is to give a detailed description of the coupled physical-biogeochemical model of the Gulf of St. Lawrence that includes dissolved oxygen and carbonate system components, as well as a detailed analysis of the riverine contribution for different nitrogen and carbonate system components. A particular attention was paid to the representation of the microbial loop in order to maintain the appropriate level of the different biogeochemical components within the system over long term simulations. The skill of the model is demonstrated using in situ data, satellite data and estimated fluxes from different studies based on observational data. The model reproduces the main features of the system such as the phytoplankton bloom, hypoxic areas, pH and calcium carbonate saturation states. The model also reproduces well the estimated transport of nitrate from one region to the other. We revisited previous estimates of the riverine nutrient contribution to surface nitrate in the Lower St. Lawrence Estuary using the model. We also explain the mechanisms that lead to high ammonium concentrations, low dissolved oxygen, and undersaturated calcium carbonate conditions on the Magdalen Shallows.

Building amorphous calcium carbonate into geochemical biomineralisation models

2020 ◽  
Author(s):  
David Evans ◽  
William Gray ◽  
James Rae ◽  
Rosanna Greenop ◽  
Paul Webb ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Isotope Fractionation ◽  
Planktonic Foraminifera ◽  
Transformation Process ◽  
Geochemical Data ◽  
Amorphous Calcium Carbonate ◽  
Carbonate System ◽  
Precursor Phase ◽  
Shell Geochemistry

<p>Amorphous calcium carbonate (ACC) has been observed, or inferred to exist, in the majority of the major phyla of marine calcifying organisms. The CaCO<sub>3</sub> produced by these organisms represents one of the largest long-term carbon sinks on Earth’s surface, such that identifying how calcification will respond to anthropogenic climate change is an urgent priority. A substantial portion of our knowledge of the biomineralisation process of these organisms is derived from inferences based on skeletal geochemical data, yet such models typically do not include an ACC component because little is known about trace element and isotope fractionation into ACC. In order to address this, we present, to our knowledge, the first structural and geochemical data of ACC precipitated from seawater under varying carbonate system conditions, seawater Mg/Ca ratios, and in the presence of three of the most common intracrystalline amino acids (aspartic acid, glutamic acid, and glycine). Based on these data we identify the carbonate system conditions necessary to produce ACC from seawater [Evans <em>et al</em>., 2019], and identify the dominant controls on ACC geochemistry. As an example, we utilise these data to build a simple biomineralisation model for the low-Mg (e.g. planktonic) foraminifera, based on precipitation of low-Mg calcite through an ACC precursor phase in a semi-enclosed pool. This exercise demonstrates that the observed shell geochemistry of this group of organisms can be fully reconciled with a model that includes an ACC component, and moreover that constraints can be placed on the degree of ACC utilisation and the ACC-calcite transformation process. More broadly, the exercise demonstrates that knowledge of the characteristics and geochemistry of ACC is important in the development of a process-based understanding of marine calcification.</p><p>Evans, D., Webb, P., Penkman, K. Kröger, R., & Allison, N. [2019] The Characteristics and Biological Relevance of Inorganic Amorphous Calcium Carbonate (ACC) Precipitated from Seawater. <em>Crystal Growth & Design</em> <strong>19</strong>: 4300.</p>

Life cycle of Calanus finmarchicus in the lower St. Lawrence Estuary: the imprint of circulation and late timing of the spring phytoplankton bloom

2001 ◽  
Vol 58 (4) ◽  
pp. 647-658 ◽  
Author(s):  
Stéphane Plourde ◽  
Pierre Joly ◽  
Jeffrey A Runge ◽  
Bruno Zakardjian ◽  
Julian J Dodson
Keyword(s):  
Population Dynamics ◽  
Life Cycle ◽  
Production Rate ◽  
Egg Production ◽  
Phytoplankton Bloom ◽  
Food Limitation ◽  
Calanus Finmarchicus ◽  
Lawrence Estuary ◽  
Egg Production Rate ◽  
St Lawrence Estuary

The life cycle of Calanus finmarchicus in the lower St. Lawrence estuary is described based on observations of female egg production rate, population stage abundance, and chlorophyll a biomass collected over 7 years (1991–1997) at a centrally located monitoring station. The mean seasonal pattern shows maximum abundance of females in May, but peak population egg production rate and naupliar (N3–N6) abundance occur in early July just after onset of the late spring – early summer phytoplankton bloom. The population stage structure is characterized by low summer abundance of early copepodite stages C1–C3 and high stage C5 abundance in autumn. Between 1994 and 1997, there was important interannual variation in both timing (up to 1 month) and amplitude (five- to eight-fold) of population reproduction. Patterns of seasonal increase of C5 abundance in autumn suggest interannual variations of both timing and magnitude of deep upstream advection of this overwintering stage. Thus, the main features of C. finmarchicus population dynamics in the central lower St. Lawrence Estuary are (i) late reproduction resulting from food limitation prior to the onset of the summer phytoplankton bloom, (ii) probable export of early developmental stages during summer, and (iii) advection into the central lower St. Lawrence Estuary of overwintering stage C5 in autumn from downstream regions. These results support the hypothesis that circulation, mainly driven by discharge from the St. Lawrence River and its tributaries, is a key factor governing population dynamics of C. finmarchicus in this region.

scholarly journals Aerobic respiration and hypoxia in the Lower St. Lawrence Estuary: Stable isotope ratios of dissolved oxygen constrain oxygen sink partitioning

2009 ◽  
Vol 54 (6) ◽  
pp. 2157-2169 ◽  
Author(s):  
Moritz F. Lehmann ◽  
Bruce Barnett ◽  
Y. Gélinas ◽  
Denis Gilbert ◽  
Roxane J. Maranger ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Dissolved Oxygen ◽  
Isotope Ratios ◽  
Aerobic Respiration ◽  
Stable Isotope Ratios ◽  
Lawrence Estuary ◽  
St Lawrence Estuary

The Limnological Units of the Lower Great Lakes - St. Lawrence River Corridor and Their Role in the Source and Aquatic Fate of Toxic Contaminants

1986 ◽  
Vol 21 (2) ◽  
pp. 168-186 ◽  
Author(s):  
R.J. Allan
Keyword(s):  
Great Lakes ◽  
Residence Time ◽  
Control Strategies ◽  
Salt Water ◽  
Transport Systems ◽  
Long Term Effects ◽  
Lawrence Estuary ◽  
St Lawrence Estuary ◽  
St Lawrence River

Abstract The waterways of the lower Great Lakes and St. Lawrence River, between Sarnia and the Saguenay Fiord, are made up of four limnological units. The first comprises the high discharge, rapid flow rivers, namely the St. Clair, Detroit, Niagara and St. Lawrence. Second are the four shallow, short residence time, riverine lakes, namely St. Clair, St. Francois, St. Louis and St. Pierre. Third are the two, relatively deep, long residence time, lower Great Lakes Erie and Ontario. Lastly, there is the freshwater-salt water mixing zone of the upper St. Lawrence Estuary. The rivers are essentially sources and transport systems of toxic contaminants on a grand scale. The riverine lakes provide only temporary storage or sinks even for contaminants associated with sediments because these are eventually resuspended and moved on downstream. The major sinks, where long-term effects are most evident are the two lower Great Lakes and the St. Lawrence Estuary. These sites are also where sediment associated contaminants can be permanently removed by deep burial in bottom sediments. However, even here, a proportion of the contaminant load passes on downstream and eventually out to the Gulf of St. Lawrence. The distinctive characteristics of the four limnological units are discussed in relation to sources and fate of toxic contaminants. Understanding the role of the units is critical to development of toxic chemicals control strategies and reduction in aquatic ecosystem contamination.

scholarly journals Impact of hypoxia on the metabolism of Greenland halibut (Reinhardtius hippoglossoides)

2013 ◽  
Vol 70 (3) ◽  
pp. 461-469 ◽  
Author(s):  
Aurélie Dupont-Prinet ◽  
Marie Vagner ◽  
Denis Chabot ◽  
Céline Audet
Keyword(s):  
Dissolved Oxygen ◽  
Metabolic Rate ◽  
Aerobic Scope ◽  
Metabolic Capacity ◽  
Greenland Halibut ◽  
Lawrence Estuary ◽  
Critical Oxygen ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
Reinhardtius Hippoglossoides ◽  
St Lawrence Estuary

Greenland halibut (Reinhardtius hippoglossoides), especially juveniles, are frequently found in severely hypoxic areas (18%–25% saturation) of the St. Lawrence Estuary. We investigated the tolerance of this species to hypoxia and evaluated the consequences of low oxygen levels on metabolic capacity. At 5 °C, juveniles had a higher critical oxygen threshold than adults (15% versus 11% saturation), indicating that they were less tolerant to hypoxia. Severe hypoxia (19% saturation) did not affect the juveniles' standard metabolic rate but significantly reduced (by 55%) their maximum metabolic rate compared with normoxia. Consequently, the aerobic scope was reduced by 72% in hypoxia compared with normoxia. In juveniles, severe hypoxia increased the duration of digestive processes. The decrease in aerobic scope in hypoxia and the determination of critical oxygen threshold at a saturation level close to actual field dissolved oxygen values strongly suggest that juveniles from the St. Lawrence Estuary are living at the edge of their metabolic capacity. Consequently, the growth and distribution of Greenland halibut could be affected if there are further declines in dissolved oxygen availability.

Holocene development of maritime ombrotrophic peatlands of the St. Lawrence North Shore in eastern Canada

2014 ◽  
Vol 82 (1) ◽  
pp. 96-106 ◽  
Author(s):  
Gabriel Magnan ◽  
Michelle Garneau ◽  
Serge Payette
Keyword(s):  
Early Developmental Stage ◽  
Larix Laricina ◽  
Eastern Canada ◽  
Peat Accumulation ◽  
Lawrence Estuary ◽  
Clay Deposits ◽  
St Lawrence Estuary ◽  
Early Developmental ◽  
Insight Into

AbstractMacrofossil analyses were used to reconstruct long-term vegetation successions within ombrotrophic peatlands (bogs) from the northern shorelines of the St. Lawrence Estuary (Baie-Comeau) and the Gulf of St. Lawrence (Havre-St-Pierre). Over the Holocene, the timing and the ecological context of peatland inception were similar in both regions and were mainly influenced by fluctuations in relative sea level. Peat accumulation started over deltaic sands after the withdrawal of the Goldthwait Sea from 7500 cal yr BP and above silt–clay deposits left by the Laurentian marine transgression after 4200 cal yr BP. In each region, the early vegetation communities were similar within these two edaphic contexts where poor fens with Cyperaceae and eastern larch (Larix laricina) established after land emergence. The rapid transitions to ombrotrophy in the peatlands of Baie-Comeau are associated with particularly high rates of peat accumulation during the early developmental stage. The results suggest that climate was more propitious to Sphagnum growth after land emergence in the Baie-Comeau area. Macrofossil data show that treeless Sphagnum-dominated bogs have persisted over millennia and that fires had few impacts on the vegetation dynamics. This study provides insight into peatland vegetation responses to climate in a poorly documented region of northeastern America.

L'alcalinité totale comme indicateur de mélange dans un milieu estuarien

1980 ◽  
Vol 17 (8) ◽  
pp. 978-984 ◽  
Author(s):  
E. Pelletier ◽  
J. Lebel
Keyword(s):  
Dissolved Oxygen ◽  
Total Alkalinity ◽  
Dilution Factor ◽  
Mixing Index ◽  
Lawrence Estuary ◽  
Estuarine Mixing ◽  
Saguenay Fjord ◽  
Saguenay River ◽  
St Lawrence Estuary ◽  
St Lawrence River

This paper proposes the use of total alkalinity as a mixing index at the mouth of Saguenay fjord on the St. Lawrence estuary. The large difference in the total alkalinity between the fresh waters from the St. Lawrence River (1.475 meq/kg) and those from the Saguenay River (0.134 meq/kg) allows us to define and calculate a dilution factor relative to total alkalinity (δAt), which is very sensitive to the presence of the fjord marine water in the estuarine mixing area both at the surface and at depth. The authors show the advantage of use of the dilution factor (δAT) in comparison to some other classical oceanographic parameters such as temperature, salinity, density, and dissolved oxygen.

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