Nutrient Distribution in the St. Lawrence Estuary

Greisman, Paul; Ingram, Grant

doi:10.1139/f77-278

Cited by 46 publications

(19 citation statements)

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“…The nutrient supply to the GSL by the LSLE was referred by Steven [1971] as the nutrient pump. Further studies suggested that within the LSLE, most of the nutrient surfacing from deeper layers occurs at a localized area at the head of the Laurentian Channel (HLC) near Tadoussac [Ingram, 1975;Greisman and Ingram, 1977;Ingram, 1979aIngram, , 1983.…”

Section: Introductionmentioning

confidence: 99%

“…This is because both the intermediate and the bottom layers are thought to be partly upwelled and vertically mixed at the HLC [Ingram, 1979a[Ingram, , 1983Saucier et al, 2009]. About 75% of the surface nutrients found in the LSLE may therefore originate from the CIL because of this upwelling/mixing mechanism [Greisman and Ingram, 1977;Savenkoff et al, 2001], the remaining part being attributed to the St. Lawrence and Saguenay rivers discharge. These vertical nutrient fluxes at the HLC sustain a high primary productivity in the LSLE, with daily production rates during the summer nearly equivalent to those during spring blooms [Levasseur et al, 1984;Therriault and Levasseur, 1985;Plourde and Runge, 1993;Plourde et al, 2001].…”

Section: Introductionmentioning

confidence: 99%

“…In contrast to previous studies which indirectly inferred vertical nutrient fluxes at the HLC [Greisman and Ingram, 1977;Savenkoff et al, 2001], this study presents direct measurements of turbulence profiles from which vertical nutrient fluxes are derived. The study focuses mainly on nitrate fluxes since dissolved nitrogen is thought to be the limiting nutrient in the system [Steven, 1974;Levasseur and Therriault, 1987].…”

Section: Introductionmentioning

confidence: 99%

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Turbulent nitrate fluxes in the Lower St. Lawrence Estuary, Canada

et al. 2015

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Turbulent vertical nitrate fluxes were calculated using new turbulent microstructure observations in the Lower St. Lawrence Estuary (LSLE), Canada. Two stations were compared: the head of the Laurentian Channel (HLC), where intense mixing occurs on the shallow sill that marks the upstream limit of the LSLE, and another station located about 100 km downstream (St. 23), more representative of the LSLE mean mixing conditions. Mean turbulent diffusivities and nitrate fluxes at the base of the surface layer for both stations were, respectively (with 95% confidence intervals): K HLC Observations suggest that the interplay between large isopleth heaving near the sill and strong turbulence is the key mechanism to sustain such high turbulent nitrate fluxes at the HLC (two to three orders of magnitude higher than those at Station 23). Calculations also suggest that nitrate fluxes at the HLC alone can sustain primary production rates of 3:4ð0:6; 11Þ g C m 22 mo 21 over the whole LSLE, approximately enough to account for a large part of the phytoplankton bloom and for most of the postbloom production. Surfacing nitrates are also believed to be consumed within the LSLE, not leaving much to be exported to the rest of the Gulf of St. Lawrence.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Turbulent nitrate fluxes in the Lower St. Lawrence Estuary, Canada

et al. 2015

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“…A priori, oceanic sources of nutrients are expected to dominate; Greisman and Ingram (1977) estimated that ~25% of the N supply to the lower estuary originates from freshwater. This potential problem will be addressed further below.…”

Section: Methodsmentioning

confidence: 99%

Mesoscale variability in nitrogen uptake rates and the f‐ratio during a coastal phytoplankton bloom

Vézina

1994

Limnology & Oceanography

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The proportion of the biological nitrogen demand met by nitrate (f-ratio) is a strong candidate for a biogeochemical parameter to relate primary production to the oceanic organic carbon flux, the latter being a potential global carbon sink. There is a controversy over whether-Scan be related to spatial and temporal variations in NO,-concentration for the purposes of estimating carbon fluxes. I report measurements of NO,-and NH, t uptake rates and of the&ratio taken during a coastal phytoplankton bloom and address the problem of mesoscale f-ratio variability.The results reveal two distinct behaviors of the f-ratio depending on light level: at the 50% level,fis nonlinearly related to ambient NO, concentration; at the 10 and 1% light levels, fis not related to NO3 concentration but is instead related to variations in the stratification in the NO,-profile. There seems to be a "two-track" biological system in the euphotic zone: a shallow food web that quickly incorporates new NO,-supplies and a deep food web that responds more slowly to a varying supply. New production tends to be higher near the surface than deeper, which is opposite the vertical structure generally proposed for NO, -limited systems. The implication is that NO, --based algorithms to predict f may not work over the full three-dimensional NO, field.

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“…The salinity of the middle estuary ranges from~0 upstream to 30 psu at the bottom of the Île-aux-Lièvres basin (El-Sabh and Silverberg, 1990;Saucier et al, 2009), and the strongest longitudinal salinity gradients are observed near the section of Île-aux-Coudres (Greisman and Ingram, 1977;Ingram and El-Sabh, 1990). The general circulation consists of a two-layer lengthwise circulation in which brackish water flows downstream over deeper, saltier water.…”

Section: Study Regionmentioning

confidence: 99%