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

Vézina, Main F.

doi:10.4319/lo.1994.39.4.0854

Cited by 13 publications

(6 citation statements)

References 13 publications

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“…Previous studies have emphasized the importance of physical (stratification, irradiance and temperature) and chemical (nutrients) control of these populations (Levasseur et al 1984, Vezina 1994, particularly with respect to the summer diatom bloom. Fewer studies have dealt with the seasonal varlation in phytoplankton communities in this environment (Levasseur et al 1984).…”

Section: Introductionmentioning

confidence: 99%

Characterization of phytoplankton communities in the lower St. Lawrence Estuary using HPLC-detected pigments and cell microscopy

Roy¹,

Chanut²,

Gosselin³

et al. 1996

Mar. Ecol. Prog. Ser.

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ABSTRACT. The seasonal v d r~a t~o nIn the coniposltlon of algal communltles In the lower St. Lawrence Estuary was examined uslng MPLC plgments and cell taxonomy, and the effic~ency of these 2 techn~ques was compared A malor centric d~a t o m bloom was observed In July 1992, preceded by an Increase In pennate d~atoms in June, l~kely caused by bottom resuspenslon due to sprlng runoff. G r a z~n g In June and July was ~n d~c a t e d by the presence of pyropheophorblde a, a copepod grazing product tracer, dnd chlorophyll degrad a t~o n plgments, l~kely assoc~ated w~t h sloppy feedlng and w~t h the presence of cells (d~atoms) wlth hlgh chlorophyllase actlvity and ac~dic cell sap. Var~ous pheopigments and degradation products of chl a \vere found In these 2 months. T h~s 1s cons~stent ivlth observat~ons of maximum abundances of major copepod specles and of herb~vorous clllates In June preceding the summer d~a t o m bloom. May was character~zed by nanoflayellates from Chrysophyceae, C~yptophyceae and Chlorophycede, lower values of algal biomdss and production and h~g h e r l~g h t harvesting effic~ency M~xlng prevented the establ~shment of vertical fluorescence patterns in May and September and probably lowered the effectwe daily light exposure of algae, w h~c h translated Into lower light accl~mat~on than In summer and h~g h e r ratios of photosynthet~c plgments to chl a. Low-l~ght acclimatlon was also observed In the deep (>20 m) June and July populat~ons, affecting marker plgment coeff~c~ents used to calculate relat~ve algal contribut~ons. Increases In relatlve amounts of chlorophyll~de a and In the allomer of chl a in September were ~nterpreted as slgns of algal senescence. The September populat~ons were coniposed of d number of chlorophyte and chrolnophyte (fucoxanth~n-conta~n~ng) algae. LOW p~gment concentratlons and lo\v numbers of observat~ons con~pl~cated the ident~f~cation task for that month. Plgment and rnlcroscoplc approaches were compared on the b a s~s of ( l ) cluster~ng, uslng each separately, (2) correlat~ons between pigments and cell groups, and (3) transformation of plgment data Into algal group contr~but~ons to chl a. The 2 approaches generally gave s~l n~l a r results even though they showed ddferent charactel-~st~cs the presence of

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Section: Introductionmentioning

confidence: 99%

Characterization of phytoplankton communities in the lower St. Lawrence Estuary using HPLC-detected pigments and cell microscopy

Roy¹,

Chanut²,

Gosselin³

et al. 1996

Mar. Ecol. Prog. Ser.

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“…no lateral transport) water mass. Vezina (1994) reported strong mesoscale variability in nitrogen uptake and the f-ratio during the 1989 bloom in the LSLE and showed that this assumption would not be valid during the phytoplankton bloom due to a lack of equilibrium between biomass increase and biomass export out of the euphotic zone. Earlier, Sinclair (1978) reported a lack of coherence in measured phytoplankton physiological state indices and questioned their utility.…”

Section: Comparisons With Other Estuarine Systemsmentioning

confidence: 99%

“…Physical conditions are also strongly dependent on atmosphenc events at synoptic or seasonal time scales (Koutitonsky & These hydrodynamic conditions show a strong spatio-temporal variability that leads to marked variability in primary and secondary production (e.g. Therriaiilt et al 3.990, de Lafontaine et al 1991, Vezina 1994. Sporadic blooms of toxic algae [Alexandriun-r sp.)…”

Section: Introductionmentioning

confidence: 99%

Late spring phytoplankton bloom in the Lower St. Lawrence Estuary:the flushing hypothesis revisited

Zakardjian

Gratton²,

Vézina

2000

Mar. Ecol. Prog. Ser.

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In the Lower St. Lawrence Estuary (LSLE), environrnental conditions (stratification, surface light and nutnents) are favorable for phytoplankton growth starting in May, but the spring phytoplankton bloom typically does not occur until early summer (late June-July). Possible explanations for the late onset of the phytoplankton bloom include flushing of the surface layer due to the spring freshwater runoff, loss of phytoplankton cells from the thin euphotic layer through sinking and rnixing, and ternperature limitation of phytoplankton growth rates. We use 1-and 2-D time-dependent models of phytoplankton dynamics to explore these hypotheses. In particular, we illustrate the role of (1) phytoplankton cell sinking versus vertical turbulent inixing and (2) flushing of freshwater runoff on pnmary production in the LSLE. Results of the 1-D simulations show the dramatic effect of phytoplankton cell sinking in a thin euphotic zone, while at the Same time high vertical turbulent mixing rnay act to maintain these sinking phytoplankton cells in the euphotic layer. Nevertheless, the 1-D analysis cannot account for spatio-temporal patterns in the development of the phytoplankton bloom observed during a high resolution physical, chernical and biological sampling field experiment perforrned in the summer of 1990 in the LSLE. 2-D simulations, run with seaward advective velocities in the range 0.15 to 0.3 m s-I, close to observed values, generate downstream patterns of phytoplankton biomass that resernble these observed patterns. Comparison with observations helps to specify the range of sinking and advective velocities that operate in concert to control the timing and spatial location of the bloom.

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“…This depth range is above the nitracline (estimated to lie between 50 and 200 m in section 3.1), but encompasses the limit often considered between the surface and the cold intermediate layer [e.g., Sinclair et al, 1976;Therriault and Levasseur, 1985;Plourde and Runge, 1993;Savenkoff et al, 2001;Plourde and Therriault, 2004]. This interval has also been chosen to represent the flux at the base of the euphotic zone, typically found at a depth of 10-20 in the LSLE [Therriault and Levasseur, 1985;Vezina, 1994 Note that for fluxes calculations at Station 23, the diffusivity profiles used are from the station itself, i.e., far from the channel sloping boundaries. As suggested by Cyr et al [2011], the fluxes reported for this station could be increased by 60% to account for boundary mixing processes.…”

Section: 1002/2014jc010272mentioning

confidence: 99%

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

Cited by 13 publications

References 13 publications

Characterization of phytoplankton communities in the lower St. Lawrence Estuary using HPLC-detected pigments and cell microscopy

Characterization of phytoplankton communities in the lower St. Lawrence Estuary using HPLC-detected pigments and cell microscopy

Late spring phytoplankton bloom in the Lower St. Lawrence Estuary:the flushing hypothesis revisited

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

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