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

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.

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

Canadian Journal of Zoology ◽

10.1139/z84-150 ◽

1984 ◽

Vol 62 (6) ◽

pp. 1048-1051 ◽

Cited By ~ 8

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.

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

Marine Environmental Research ◽

10.1016/j.marenvres.2006.12.003 ◽

2007 ◽

Vol 63 (5) ◽

pp. 490-505 ◽

Cited By ~ 19

Author(s):

Patrick Poulin ◽

Emilien Pelletier ◽

Richard Saint-Louis

Keyword(s):

Salt Marshes ◽

Seasonal Variability ◽

Lawrence Estuary ◽

St Lawrence Estuary

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Dynamics of carbon assimilation by St Lawrence estuary phytoplankton at the end of summer

Hydrobiologia ◽

10.1007/bf00041460 ◽

1990 ◽

Vol 207 (1) ◽

pp. 227-232 ◽

Cited By ~ 3

Author(s):

Chantal Descolas-Gros ◽

Michel R. Fontugne

Keyword(s):

Carbon Assimilation ◽

Lawrence Estuary ◽

St Lawrence Estuary

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

Environmental Conservation ◽

10.1017/s0376892910000184 ◽

2009 ◽

Vol 36 (4) ◽

pp. 312-320 ◽

Cited By ~ 19

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.

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

Wetlands Ecology and Management ◽

10.1007/s11273-009-9141-y ◽

2009 ◽

Vol 17 (6) ◽

pp. 655-673 ◽

Cited By ~ 6

Author(s):

Patrick Poulin ◽

Émilien Pelletier ◽

Vladimir G. Koutitonski ◽

Urs Neumeier

Keyword(s):

Salt Marshes ◽

Nutrient Fluxes ◽

Lawrence Estuary ◽

St Lawrence Estuary

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

Revue des sciences de l eau ◽

10.7202/045097ar ◽

2010 ◽

Vol 23 (4) ◽

pp. 349-358 ◽

Cited By ~ 2

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.

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The biology of Gammarus (Crustacea, Amphipoda) in the northwestern Atlantic. VI. Gammarus tigrinus Sexton

Canadian Journal of Zoology ◽

10.1139/z72-144 ◽

1972 ◽

Vol 50 (8) ◽

pp. 1063-1068 ◽

Cited By ~ 12

Author(s):

D. H. Steele ◽

V. J. Steele

Keyword(s):

Life Cycle ◽

Late Summer ◽

Lawrence Estuary ◽

Gammarus Tigrinus ◽

Estuarine Species ◽

St Lawrence Estuary

Gammarus tigrinus is an endemic estuarine species of the northwestern Atlantic found from the St. Lawrence estuary south to Florida. At St. Andrews, N.B., 50% maturity occurs at 6.1 mm in the female. Females produce a series of broods between April and September at which time they enter the resting stage. The oogonia begin to enlarge in February, but are not fertilized until April. The young hatched in the spring probably enter the resting stage in late summer before producing the first brood. The older generation disappears in the summer and the life cycle is annual.

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

Biogeosciences ◽

10.5194/bg-10-7609-2013 ◽

2013 ◽

Vol 10 (11) ◽

pp. 7609-7622 ◽

Cited By ~ 13

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.

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