Benthic diatom communities from two salt marshes of the St. Lawrence Estuary (Canada)

2010 ◽  
Vol 23 (4) ◽  
pp. 349-358 ◽  
Author(s):  
Michèle A. De Sève ◽  
Patrick Poulin ◽  
Émilien Pelletier ◽  
Karine Lemarchand
Keyword(s):  
Salt Marshes ◽  
Extracellular Polymeric Substances ◽  
The Other ◽  
High Marsh ◽  
Biological Index ◽  
Sediment Grain Size ◽  
Lawrence Estuary ◽  
Marsh Area ◽  
Diatom Communities ◽  
St Lawrence Estuary

Microphytobenthic diatom communities were investigated in the high and low sections of two salt marshes of the Lower St. Lawrence Estuary (eastern Canada): one featuring a sandy low marsh zone (Pointe-aux-Épinettes; PE) and one with a muddy low marsh area (Pointe-au-Père; PP). Based on diatom composition and diversity, bacterial abundance, chlorophyll-a, phaeopigments and geochemical analyses (Corg, Ntot, granulometry, extracellular polymeric substances), the PP high marsh area appeared to be singular compared to the other sampling sites. Estimated surface biomass ranged from 11 to 71 g C•m-2in the PE marsh and from 24 to 486 g C•m-2in the PP marsh. A higher diversity of diatom species was observed in the PP high marsh area with a dominance of epipelic forms, in opposition to the dominant epipsammic forms at the other sites. Statistical analyses showed that diatom density was mainly affected by nutrient availability while the relative abundance of epipelic and epipsammic species was related to sediment grain size. This study provides original data on the composition of benthic diatoms in surface sediments in St. Lawrence saltmarshes during summer time that represent the first step to the determination of the DBI (Diatom biological index) of these northern environments.

Salinity tolerances and preferences of fry of two species of sympatric sticklebacks: possible mechanisms of habitat segregation

1984 ◽  
Vol 62 (6) ◽  
pp. 1048-1051 ◽  
Author(s):  
Suzanne Campeau ◽  
Helga Guderley ◽  
Gerard Fitzgerald
Keyword(s):  
Salt Marshes ◽  
Gasterosteus Aculeatus ◽  
Reproductive Activity ◽  
Tidal River ◽  
Differential Distribution ◽  
Lawrence Estuary ◽  
Parental Stock ◽  
Salinity Preference ◽  
Tolerance Field ◽  
St Lawrence Estuary

During their period of reproductive activity, the sticklebacks Gasterosteus aculeatus (trachurus) and Gasterosteus wheatlandi show differences in their use of available microhabitats in the salt marshes of the St. Lawrence estuary. Gasterosteus aculeatus is found at all stations along a tidal river, Rivière des Vases, while G. wheatlandi is absent from the sites exposed to freshwater. To determine whether the juveniles of these species have different sensitivities to low salinities which could account for their differential distribution, we examined the salinity tolerances of laboratory-reared fry. Adult G. aculeatus (form trachurus) and G. wheatlandi collected at the mouth of the Rivière des Vases were used as the parental stock. For 1-week-old fry of both species, freshwater represented a marginal environment. Following exposure to freshwater for 96 h, G. aculeatus fry showed a 22% mortality while G. wheatlandi showed a significant decrease in growth. By 5 weeks of age, both species were euryhaline. Despite a wide salinity tolerance, field-collected G. wheatlandi significantly preferred a salinity of 7–14‰ while field-collected G. aculeatus fry showed no significant salinity preference.

Le contrôle de la variabilité à court terme du phytoplancton estuarien: stabilité verticale et profondeur critique

1979 ◽  
Vol 36 (11) ◽  
pp. 1325-1335 ◽  
Author(s):  
L. Fortier ◽  
L. Legendre
Keyword(s):  
Water Column ◽  
Tidal Cycle ◽  
Richardson Number ◽  
Low Frequency ◽  
The Other ◽  
Critical Depth ◽  
Lawrence Estuary ◽  
Vertical Stability ◽  
St Lawrence Estuary ◽  
C Assimilation

Hourly series of summer phytoplankton biomass (ATP and chlorophyll a) and photosynthetic capacity (14C assimilation and ATP increase in saturating light) were sampled in the lower St. Lawrence Estuary during the summer of 1977. Vertical stability of the water column was estimated by the Richardson number. From the results it is concluded that the mean level of biomass is an inverse function of critical depth, likely linked to the neap-spring tidal cycle (Mf). On the other hand, the fine fluctuations of biomass and photosynthetic activity were related to vertical stability, which varies according to the semi-diurnal tidal cycle (M2). A simple model was developed on the basis of Sverdrup's critical depth, combining the M2 fluctuations in stability (degree of vertical mixing) to Mf variations in critical depth. Net biomass increases, observed in a nonturbid stabilized water column, cannot be explained by the growth rates computed from 14C assimilation, but they are consistent with the measured rates of ATP production. Spectral analyses of time series of temperature and Richardson number suggest that low frequency water column stability variations amplify the spatial heterogeneity of a reacting parameter such as phytoplankton. On the other hand, a passive scalar such as temperature does not respond to these low frequency variations of stability. It follows that the study of stability spectra may give some insight into the low frequency control of phytoplankton dynamics. Key words: phytoplankton, St. Lawrence Estuary, variability, vertical stability, critical depth, Richardson number, Kendall's cross correlation, spectral analysis

scholarly journals Seasonal variability of denitrification efficiency in northern salt marshes: An example from the St. Lawrence Estuary

2007 ◽  
Vol 63 (5) ◽  
pp. 490-505 ◽  
Author(s):  
Patrick Poulin ◽  
Emilien Pelletier ◽  
Richard Saint-Louis
Keyword(s):  
Salt Marshes ◽  
Seasonal Variability ◽  
Lawrence Estuary ◽  
St Lawrence Estuary

The effects of drought and waterlogging conditions on the performance of an endemic annual plant, Aster laurentianus

2000 ◽  
Vol 78 (1) ◽  
pp. 40-46 ◽  
Author(s):  
Gilles Houle ◽  
Annie Belleau
Keyword(s):  
Salt Marshes ◽  
Carbon Assimilation ◽  
Late Summer ◽  
Annual Plant ◽  
Endemic Plant ◽  
Lawrence Estuary ◽  
Negative Effect ◽  
Effects Of Drought ◽  
Interannual Fluctuations ◽  
St Lawrence Estuary

Aster laurentianus Fernald is an annual plant endemic to the St. Lawrence estuary. It typically grows in salt marshes at the periphery of shallow lagoons. In this habitat, the water level fluctuates greatly both within and between years. Such fluctuations may induce significant interannual variations in marsh-plant populations. In this study, we experimentally determined the effects of different water availability conditions, imposed at various stages of plant development, on the performance of A. laurentianus. Waterlogging had no significant effect on net carbon assimilation rate, plant growth, and biomass allocation. However, a drought stress at the time of reproductive-bud differentiation had a negative effect on flower-head production. We propose that occasional reproductive failures resulting from late-summer droughts may cause significant interannual fluctuations in the size of A. laurentianus populations, potentially making them more susceptible to local extinction.Key words: Aster laurentianus, endemic plant, Îles-de-la-Madeleine, rare plant, salt marshes, water stress.

Soil carbon may be maintained under grazing in a St Lawrence Estuary tidal marsh

2009 ◽  
Vol 36 (4) ◽  
pp. 312-320 ◽  
Author(s):  
O.T. YU ◽  
G.L. CHMURA
Keyword(s):  
Organic Matter ◽  
Soil Carbon ◽  
Salt Marshes ◽  
Carbon Sink ◽  
Economic Incentive ◽  
Plant Litter ◽  
Root Production ◽  
Belowground Production ◽  
Lawrence Estuary ◽  
St Lawrence Estuary

SUMMARYProduction of belowground organic matter is critical to sustainability of salt marshes. It plays a role in vertical soil accretion, a process essential for salt marshes to maintain their relative elevation and persist as sea levels rise. This paper examines belowground production and soil carbon of a high-latitude saltmarsh in the St Lawrence Estuary (Québec, Canada), which had been subjected to six years of sheep grazing. In the seventh year, without sheep, organic matter production in grazed and ungrazed sections was assessed by examining harvests of plant litter, end-of-season standing crop, and the roots and rhizomes present in in-growth cores. Excepting salinity, porewater chemistry varied little. The grazed marsh had higher soil carbon density and belowground production, yet lower aboveground biomass. Grazing reduces plant litter and increases solar exposure, soil temperature (at this latitude, soil remained frozen until April) and evapotranspiration, thus raising soil salinity and nitrogen demand, the latter a driver of root production. Grazing may not be detrimental to soil carbon storage. Permitting certain types of grazing on restored salt marshes previously drained for agriculture would provide economic incentive to restore tidal flooding, because the natural carbon sink provided in the recovered marsh would make these lands eligible for carbon payments.

Electrogenic sulfur oxidation in a northern saltmarsh (St. Lawrence Estuary, Canada)

2016 ◽  
Vol 62 (6) ◽  
pp. 530-537 ◽  
Author(s):  
Alexandra Rao ◽  
Nils Risgaard-Petersen ◽  
Urs Neumeier
Keyword(s):  
Sediment Cores ◽  
Sulfur Oxidation ◽  
High Marsh ◽  
Lawrence Estuary ◽  
Prolonged Incubation ◽  
Geochemical Fingerprint ◽  
Creek Bank ◽  
Marsh Sediments ◽  
St Lawrence Estuary

Measurements of porewater O2, pH, and H2S microprofiles in intact sediment cores collected in a northern saltmarsh in the St. Lawrence Estuary (Quebec, Canada) revealed the occurrence of electrogenic sulfur oxidation (e-SOx) by filamentous “cable” bacteria in submerged marsh pond sediments in the high marsh. In summer, the geochemical fingerprint of e-SOx was apparent in intact cores, while in fall, cable bacteria were detected by fluorescence in situ hybridization and the characteristic geochemical signature of e-SOx was observed only upon prolonged incubation. In exposed, unvegetated creek bank sediments sampled in the low marsh in summer, cable bacteria developed only in repacked cores of sieved (500 μm), homogenized sediments. These results suggest that e-SOx is suppressed by the activity of macrofauna in exposed, unvegetated marsh sediments. A reduced abundance of benthic invertebrates may promote e-SOx development in marsh ponds, which are dominant features of subarctic saltmarshes as in the St. Lawrence Estuary.

Seasonal nutrient fluxes variability of northern salt marshes: examples from the lower St. Lawrence Estuary

2009 ◽  
Vol 17 (6) ◽  
pp. 655-673 ◽  
Author(s):  
Patrick Poulin ◽  
Émilien Pelletier ◽  
Vladimir G. Koutitonski ◽  
Urs Neumeier
Keyword(s):  
Salt Marshes ◽  
Nutrient Fluxes ◽  
Lawrence Estuary ◽  
St Lawrence Estuary

Croissance de la plie rouge (Pseudopleuronectes americanus) de l'estuaire maritime du Saint-Laurent

1985 ◽  
Vol 63 (7) ◽  
pp. 1610-1616 ◽  
Author(s):  
Robert Vaillancourt ◽  
Jean-Claude F. Brêthes ◽  
Gaston Desrosiers
Keyword(s):  
Linear Growth ◽  
Sampling Period ◽  
The Other ◽  
Pseudopleuronectes Americanus ◽  
Spawning Period ◽  
Lawrence Estuary ◽  
Growth Equations ◽  
South Shore ◽  
Males And Females ◽  
St Lawrence Estuary

A study on the growth in size and weight of the Winter Flounder, Pseudopleuronectes americanus (Walbaum), was conducted from samples collected during the summers of 1979 and 1980, in the bay of Saint-Fabien-sur-Mer (Québec) on the south shore of the Lower St. Lawrence Estuary. Age was determined by otolith readings and length–weight relationships were calculated. Linear growth equations were not statistically different for males and females. On the other hand, weight was found to be higher for females than for males of equal sizes. This relationship also varies with the sampling period, and a substantial weight increase follows the spawning period. The growth of P. americanus is slower in the estuary than in more southern areas, while the weights at equal sizes are higher. These results reflect the severe environmental conditions, which necessitate a large accumulation of food energy by the fish as reserves, to the detriment of growth.

scholarly journals Benthic fluxes of dissolved organic nitrogen in the lower St. Lawrence estuary and implications for selective organic matter degradation

2013 ◽  
Vol 10 (11) ◽  
pp. 7609-7622 ◽  
Author(s):  
M. Alkhatib ◽  
P. A. del Giorgio ◽  
Y. Gelinas ◽  
M. F. Lehmann
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Bottom Water ◽  
Estuarine Sediments ◽  
Internal Source ◽  
Lawrence Estuary ◽  
Element Partitioning ◽  
Sediment Porewaters ◽  
St Lawrence Estuary

Abstract. The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment porewaters was determined at nine locations along the St. Lawrence estuary and in the gulf of St. Lawrence. In a previous manuscript (Alkhatib et al., 2012a), we have shown that this study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, and benthic respiration rates. Based on the porewater profiles, we estimated the benthic diffusive fluxes of DON and DOC in the same area. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1). DON fluxes were positively correlated with sedimentary POM reactivity and varied inversely with sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30 to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange, a result that is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. In contrast to DON, DOC fluxes out of the sediments did not show any significant spatial variation along the Laurentian Channel (LC) between the estuary and the gulf (2100 ± 100 μmol m−2 d−1). The molar C / N ratio of dissolved organic matter (DOM) in porewater and the overlying bottom water varied significantly along the transect, with lowest C / N in the lower estuary (5–6) and highest C / N (> 10) in the gulf. Large differences between the C / N ratios of porewater DOM and POM are mainly attributed to a combination of selective POM hydrolysis and elemental fractionation during subsequent DOM mineralization, but selective adsorption of DOM to mineral phases could not be excluded as a potential C / N fractionating process. The extent of this C- versus N- element partitioning seems to be linked to POM reactivity and redox conditions in the sediment porewaters. Our results thus highlight the variable effects selective organic matter (OM) preservation can have on bulk sedimentary C / N ratios, decoupling the primary source C / N signatures from those in sedimentary paleoenvironmental archives. Our study further underscores that the role of estuarine sediments as efficient sinks of bioavailable nitrogen is strongly influenced by the release of DON during early diagenetic reactions, and that DON fluxes from continental margin sediments represent an important internal source of N to the ocean.

Pre-exposure to Cu2+ and CuO NPs leads to infection of caged blue mussels, Mytilus edulis L., by pathogenic microalga: Pilot study in the Lower St. Lawrence Estuary (Québec, Canada)

2021 ◽  
Vol 166 ◽  
pp. 112180
Author(s):  
Michael Zuykov ◽  
Galina Kolyuchkina ◽  
Graeme Spiers ◽  
Michel Gosselin ◽  
Philippe Archambault ◽  
...  
Keyword(s):  
Pilot Study ◽  
Mytilus Edulis ◽  
Lawrence Estuary ◽  
Blue Mussels ◽  
Cuo Nps ◽  
St Lawrence Estuary
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