Influence of dinoflagellate diurnal vertical migrations on dimethylsulfoniopropionate and dimethylsulfide distribution and dynamics (St. Lawrence Estuary, Canada)

2004 ◽  
Vol 61 (5) ◽  
pp. 712-720 ◽  
Author(s):  
Anissa Merzouk ◽  
Maurice Levasseur ◽  
Michael Scarratt ◽  
Sonia Michaud ◽  
Michel Gosselin
Keyword(s):  
Vertical Migration ◽  
De Novo ◽  
Physiological Responses ◽  
Alexandrium Tamarense ◽  
Scrippsiella Trochoidea ◽  
Lawrence Estuary ◽  
Chl A ◽  
Diel Variations ◽  
St Lawrence Estuary ◽  
Diurnal Vertical Migrations

The influence of the diurnal vertical migration of the dinoflagellates Alexandrium tamarense and Scrippsiella trochoidea on dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) dynamics was studied during a 34-h Lagrangian experiment in the St. Lawrence Estuary in July 2000. Particulate DMSP (DMSPp), dissolved DMSP (DMSPd), and DMS exhibited diel patterns with minimum concentrations during the night and maximum concentrations around noon. DMSPp concentrations were correlated with the abundance of the two vertically migrating DMSP-rich dinoflagellates. The DMSPp:Chl a ratio exhibited similar diel variations, suggesting a light-induced de novo DMSP synthesis during the day. Diel variations of the DMS:Chl a ratio suggest that the accumulation of DMS around noon resulted from physiological responses of the algae and (or) bacteria to light. Biological gross DMS production and bacterial DMS consumption were decoupled, leading to rapid fluctuations in DMS. These results show that in systems dominated by DMSP-rich dinoflagellates containing DMSP lyases, DMS concentrations may vary by as much as a factor of 10 over a 24-h period. Such diel variations must be considered when estimating the contribution of such systems to the DMS sea to air flux.

A biophysical model of the interaction between vertical migration of crustacean zooplankton and circulation in the Lower St. Lawrence Estuary

1999 ◽  
Vol 56 (12) ◽  
pp. 2420-2432 ◽  
Author(s):  
Bruno A Zakardjian ◽  
Jeffrey A Runge ◽  
Stephane Plourde ◽  
Yves Gratton
Keyword(s):  
Population Dynamics ◽  
Vertical Migration ◽  
Horizontal Distribution ◽  
Calanus Finmarchicus ◽  
Biophysical Model ◽  
Crustacean Zooplankton ◽  
Simple Formulation ◽  
Lawrence Estuary ◽  
Circulation Patterns ◽  
St Lawrence Estuary

As an essential step in modeling the influence of circulation on the population dynamics of marine planktonic copepods, we define a simple formulation of swimming behavior that can be used in both Eulerian and Lagrangian models. This formulation forces aggregation of the population toward a preferential depth and can be stage specific and time varying, thus allowing description of either diurnal or seasonal vertical migration. We use the formulation to examine the interaction between the circulation and vertical distribution in controlling horizontal distribution of the common planktonic copepod Calanus finmarchicus in the Lower St. Lawrence Estuary, Canada. We first introduce diel migration into a simple one-dimensional model and then into a model of residual two-dimensional circulation patterns representative of conditions encountered in the Lower St. Lawrence Estuary. Results from the latter indicate that interactions between circulation and stage-specific swimming behaviors are the main mechanisms for aggregation of planktonic crustaceans at the head of the Laurentian Channel and highlight the implications of flushing of the surface-dwelling young stages for the population dynamics of C. finmarchicus in the Lower St. Lawrence Estuary.

CONTROL OF GERMINATION OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE) CYSTS FROM THE LOWER ST. LAWRENCE ESTUARY (CANADA)

1998 ◽  
Vol 34 (2) ◽  
pp. 242-249 ◽  
Author(s):  
Catalina Castell Perez ◽  
Suzanne Roy ◽  
Maurice Levasseur ◽  
Donald M. Anderson
Keyword(s):  
Alexandrium Tamarense ◽  
Lawrence Estuary ◽  
St Lawrence Estuary

scholarly journals Experimental assessment of the sensitivity of an estuarine phytoplankton fall bloom to acidification and warming

2018 ◽  
Vol 15 (16) ◽  
pp. 4883-4904 ◽  
Author(s):  
Robin Bénard ◽  
Maurice Levasseur ◽  
Michael Scarratt ◽  
Marie-Amélie Blais ◽  
Alfonso Mucci ◽  
...  
Keyword(s):  
Growth Rate ◽  
Primary Production ◽  
Net Primary Production ◽  
Skeletonema Costatum ◽  
Potential Effect ◽  
Lawrence Estuary ◽  
Chl A ◽  
Wide Range ◽  
To Come ◽  
St Lawrence Estuary

Abstract. We investigated the combined effect of ocean acidification and warming on the dynamics of the phytoplankton fall bloom in the Lower St. Lawrence Estuary (LSLE), Canada. Twelve 2600 L mesocosms were set to initially cover a wide range of pHT (pH on the total proton scale) from 8.0 to 7.2 corresponding to a range of pCO2 from 440 to 2900 µatm, and two temperatures (in situ and +5 ∘C). The 13-day experiment captured the development and decline of a nanophytoplankton bloom dominated by the chain-forming diatom Skeletonema costatum. During the development phase of the bloom, increasing pCO2 influenced neither the magnitude nor the net growth rate of the nanophytoplankton bloom, whereas increasing the temperature by 5 ∘C stimulated the chlorophyll a (Chl a) growth rate and maximal particulate primary production (PP) by 76 % and 63 %, respectively. During the declining phase of the bloom, warming accelerated the loss of diatom cells, paralleled by a gradual decrease in the abundance of photosynthetic picoeukaryotes and a bloom of picocyanobacteria. Increasing pCO2 and warming did not influence the abundance of picoeukaryotes, while picocyanobacteria abundance was reduced by the increase in pCO2 when combined with warming in the latter phase of the experiment. Over the full duration of the experiment, the time-integrated net primary production was not significantly affected by the pCO2 treatments or warming. Overall, our results suggest that warming, rather than acidification, is more likely to alter phytoplankton autumnal bloom development in the LSLE in the decades to come. Future studies examining a broader gradient of temperatures should be conducted over a larger seasonal window in order to better constrain the potential effect of warming on the development of blooms in the LSLE and its impact on the fate of primary production.

Wind-driven river plume dynamics and toxic Alexandrium tamarense blooms in the St. Lawrence estuary (Canada): A modeling study

Harmful Algae ◽  
2008 ◽  
Vol 7 (2) ◽  
pp. 214-227 ◽  
Author(s):  
Juliette Fauchot ◽  
François J. Saucier ◽  
Maurice Levasseur ◽  
Suzanne Roy ◽  
Bruno Zakardjian
Keyword(s):  
River Plume ◽  
Alexandrium Tamarense ◽  
Lawrence Estuary ◽  
Plume Dynamics ◽  
St Lawrence Estuary ◽  
Modeling Study

scholarly journals Experimental assessment of the sensitivity of an estuarine phytoplankton fall bloom to acidification and warming

2018 ◽  
Author(s):  
Robin Bénard ◽  
Maurice Levasseur ◽  
Michael Grant Scarratt ◽  
Marie-Amélie Blais ◽  
Alfonso Mucci ◽  
...  
Keyword(s):  
Growth Rate ◽  
Primary Production ◽  
Skeletonema Costatum ◽  
Potential Effect ◽  
Lawrence Estuary ◽  
Chl A ◽  
Wide Range ◽  
To Come ◽  
Two Phases ◽  
St Lawrence Estuary

Abstract. We investigated the combined effect of ocean acidification and warming on the dynamics of the phytoplankton fall bloom in the Lower St. Lawrence Estuary (LSLE), Canada. Twelve 2600 L mesocosms were set to initially cover a wide range of pHT (pH on the total proton scale) from 8.0 to 7.2 corresponding to a range of pCO2 from 440 to 2900 µatm, and two temperatures (in situ and +5 °C). The 13-day experiment captured the development and decline of a nanophytoplankton bloom dominated by the chain-forming diatom Skeletonema costatum. During the development phase of the bloom, increasing pCO2 influenced neither the magnitude nor the net growth rate of the nanophytoplankton bloom whereas increasing the temperature by 5 °C stimulated the chlorophyll a (Chl a) growth rate and particulate primary production (PP) by 50 % and 160 %, respectively. During the declining phase of the bloom, warming accelerated the loss of diatom cells and negatively affected PP. Due to the countervailing responses of the plankton community to warming during the two phases of the experiment, the time-integrated primary production was not significantly affected over the full duration of the study. The diatom bloom was paralleled by a gradual decrease in the abundance of photosynthetic picoeukaryotes and followed by a bloom of picocyanobacteria. Increasing pCO2 and warming did not influence the abundance of picoeukaryotes, but warming stimulated picocyanobacteria proliferation. Overall, our results suggest that warming, rather than acidification, is more likely to alter phytoplankton autumnal bloom development in the LSLE in the decades to come. Future studies examining a broader gradient of temperatures should be conducted over a larger seasonal window in order to better constrain the potential effect of warming on the development of blooms in the LSLE and its impact on the fate of primary production.

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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