Modelling the Initiation of Spring Phytoplankton Blooms: a Synthesis of Physical and Biological Interannual Variability off Southwest Nova Scotia, 1983–85

1989 ◽  
Vol 46 (S1) ◽  
pp. s183-s199 ◽  
Author(s):  
R. Ian Perry ◽  
Peter C. F. Hurley ◽  
Peter C. Smith ◽  
J. Anthony Koslow ◽  
Robert O. Fournier
Keyword(s):  
Nova Scotia ◽  
Mixed Layer ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
Critical Value ◽  
Zooplankton Biomass ◽  
Phytoplankton Production ◽  
Spring Phytoplankton Bloom ◽  
Turbulent Dissipation ◽  
Differential Advection

Chlorophyll and nitrate data from monthly surveys off southwest Nova Scotia indicate the spring phytoplankton bloom began near the end of March of each year, occurring early (late) in 1984 (1983). The highest chlorophyll biomass(all months) was found in 1985. Using survey data, the Sverdrup hypothesis for the initiation of the bloom was tested by comparing the critical depth, Zcr, for net phytoplankton production to the observed mixed-layer depth, Zmix. Survey median Zcr/Zmix were consistently less than 1 until May, suggesting that observed blooms were initiated by events outside the specific survey periods. Results of a mixed-layer model incorporating surface heating, differential advection and turbulent dissipation by wind and tide showed reasonable agreement with observed mixed depths, and patterns of the mean (modelled) mixed-layer light intensity are significantly correlated with observed chlorophyll biomass. In 1983 and 1984, mean light intensities first exceeded the critical value for a bloom to occur in late March. In 1985, transient periods of stratification in mid-February and early March produced intensities greater than the critical value. These events, together with higher nitrate concentrations and lower Zooplankton biomass, appear to be responsible for the high chlorophyll biomass observed in 1985.

scholarly journals A newly observed physical cause of the onset of the subsurface spring phytoplankton bloom in the southwestern East Sea/Sea of Japan

2014 ◽  
Vol 11 (5) ◽  
pp. 1319-1329 ◽  
Author(s):  
Y.-T. Son ◽  
K.-I. Chang ◽  
S.-T. Yoon ◽  
T. Rho ◽  
J. H. Kwak ◽  
...  
Keyword(s):  
Sea Of Japan ◽  
Mixed Layer ◽  
Spring Bloom ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
East Sea ◽  
Ulleung Basin ◽  
Intermediate Water ◽  
Spring Phytoplankton Bloom ◽  
Bloom Period

Abstract. An ocean buoy, UBIM (Ulleung Basin Integrated Mooring), deployed during the spring transition from February to May 2010 reveals for the first time highly resolved temporal variation of biochemical properties of the upper layer of the Ulleung Basin in the southwestern East Sea/Sea of Japan. The time-series measurement captured the onset of subsurface spring bloom at 30 m, and collocated temperature and current data gives an insight into a mechanism that triggers the onset of the spring bloom not documented so far. Low-frequency modulation of the mixed layer depth ranging from 10 m to 53 m during the entire mooring period is mainly determined by shoaling and deepening of isothermal depths depending on the placement of UBIM on the cold or warm side of the frontal jet. The occurrence of the spring bloom at 30 m is concomitant with the appearance of colder East Sea Intermediate Water at buoy UBIM, which results in subsurface cooling and shoaling of isotherms to the shallower depth levels during the bloom period than those that occurred during the pre-bloom period. Isolines of temperature-based NO3 are also shown to be uplifted during the bloom period. It is suggested that the springtime spreading of the East Sea Intermediate Water is one of the important factors that triggers the subsurface spring bloom below the mixed layer.

scholarly journals Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom

2014 ◽  
Vol 112 (1) ◽  
pp. E15-E20 ◽  
Author(s):  
Michael J. Ellwood ◽  
David A. Hutchins ◽  
Maeve C. Lohan ◽  
Angela Milne ◽  
Philipp Nasemann ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Mixed Layer ◽  
Phytoplankton Bloom ◽  
Iron Bioavailability ◽  
Global Ocean ◽  
Minor Role ◽  
Surface Mixed Layer ◽  
Spring Phytoplankton Bloom ◽  
Dissolved Iron ◽  
Particulate Iron

The supply and bioavailability of dissolved iron sets the magnitude of surface productivity for ∼40% of the global ocean. The redox state, organic complexation, and phase (dissolved versus particulate) of iron are key determinants of iron bioavailability in the marine realm, although the mechanisms facilitating exchange between iron species (inorganic and organic) and phases are poorly constrained. Here we use the isotope fingerprint of dissolved and particulate iron to reveal distinct isotopic signatures for biological uptake of iron during a GEOTRACES process study focused on a temperate spring phytoplankton bloom in subtropical waters. At the onset of the bloom, dissolved iron within the mixed layer was isotopically light relative to particulate iron. The isotopically light dissolved iron pool likely results from the reduction of particulate iron via photochemical and (to a lesser extent) biologically mediated reduction processes. As the bloom develops, dissolved iron within the surface mixed layer becomes isotopically heavy, reflecting the dominance of biological processing of iron as it is removed from solution, while scavenging appears to play a minor role. As stable isotopes have shown for major elements like nitrogen, iron isotopes offer a new window into our understanding of the biogeochemical cycling of iron, thereby allowing us to disentangle a suite of concurrent biotic and abiotic transformations of this key biolimiting element.

scholarly journals Numerical simulations of the competition between wind-driven mixing and surface heating in triggering spring phytoplankton blooms

2015 ◽  
Vol 72 (6) ◽  
pp. 1926-1941 ◽  
Author(s):  
Rica Mae Enriquez ◽  
John R. Taylor
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mixed Layer ◽  
Turbulent Mixing ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
Phytoplankton Growth ◽  
Surface Heating ◽  
Surface Mixed Layer ◽  
Critical Depth

Abstract About 60 years ago, Sverdrup formalized the critical depth hypothesis to explain the timing of the spring phytoplankton bloom in terms of the depth of the surface mixed layer. In recent years, a number of refinements and alternatives to the critical depth hypothesis have been proposed, including the critical turbulence hypothesis which states that a bloom can occur when turbulent mixing is sufficiently weak, irrespective of the mixed layer depth. Here, we examine the relative influence of wind-driven mixing and net surface heating on phytoplankton growth. Of particular interest is whether wind-driven mixing can delay the spring bloom after winter convection gives way to net surface warming. We address these questions using high-resolution large-eddy simulations (LES) coupled with a simple phytoplankton model. We also describe an analytical phytoplankton model with a formulation for the turbulent mixing based on the LES results. For a constant, prescribed surface heat flux, net phytoplankton growth is seen when the windstress is smaller than a critical value. Similarly, for a constant windstress, a critical heat flux separates cases with growing and decaying phytoplankton populations. Using the LES results, we characterize the critical windstress and critical heat flux in terms of other physical and biological parameters and propose a simple expression for each based on the analysis of the analytical model. Phytoplankton growth begins when the mixing depth shoals above the critical depth, consistent with the critical depth hypothesis. Our results provide a framework to interpret blooms in other conditions where both the depth and the intensity of turbulent mixing might be crucial factors in influencing phytoplankton growth.

scholarly journals Phytoplankton bloom phenomena in the North Atlantic Ocean and Arabian Sea

2015 ◽  
Vol 72 (6) ◽  
pp. 2021-2028 ◽  
Author(s):  
John F. Marra ◽  
Tommy D. Dickey ◽  
Albert J. Plueddemann ◽  
Robert A. Weller ◽  
Christopher S. Kinkade ◽  
...  
Keyword(s):  
Water Column ◽  
Mixed Layer ◽  
Arabian Sea ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
Ocean Dynamics ◽  
Layer Depth ◽  
Diurnal Variability ◽  
Water Column Stratification ◽  
Iceland Basin

Abstract We review bio-optical and physical data from three mooring experiments, the Marine Light–Mixed Layers programme in spring 1989 and 1991 in the Iceland Basin (59°N/21°W), and the Forced Upper Ocean Dynamics Experiment in the central Arabian Sea from October 1994 to 1995 (15.5°N/61.5°E). In the Iceland Basin, from mid-April to mid-June in 1989, chlorophyll-a concentrations are sensitive to small changes in stratification, with intermittent increases early in the record. The spring increase occurs after 20 May, coincident with persistent water column stratification. In 1991, the bloom occurs 2 weeks earlier than in 1989, with a background of strong short-term and diurnal variability in mixed layer depth and minimal horizontal advection. In the Arabian Sea, the mixing response to the northeast and southwest monsoons, plus the response to mesoscale eddies, produces four blooms over the annual cycle. The mixed layer depth in the Arabian Sea never exceeds the euphotic zone, allowing interactions between phytoplankton and grazer populations to become important. For all three mooring experiments, change in water column stratification is key in producing phytoplankton blooms.

scholarly journals Synoptic-Scale Atmospheric Motions Modulated by Spring Phytoplankton Bloom in the Sea of Japan

2014 ◽  
Vol 27 (20) ◽  
pp. 7587-7602 ◽  
Author(s):  
Atsuhiko Isobe ◽  
Shin’ichiro Kako ◽  
Shinsuke Iwasaki
Keyword(s):  
Sea Of Japan ◽  
Mixed Layer ◽  
Phytoplankton Bloom ◽  
The Sea Of Japan ◽  
Layer Model ◽  
Spring Phytoplankton Bloom ◽  
Attenuation Coefficients ◽  
Air Mass ◽  
Dry Air ◽  
Mixed Layer Model

Abstract Atmospheric responses to biological heating caused by the spring phytoplankton bloom in the Sea of Japan are investigated. Sea surface temperature (SST) is first computed using a mixed-layer model with an ocean reanalysis product. Satellite-derived surface chlorophyll concentrations representing phytoplankton population are input to an equation for attenuation coefficients of solar radiation penetrating the mixed layer. Two sets of SST are obtained by this model, using the attenuation coefficients with and without phytoplankton. It is found that the phytoplankton bloom increases SST by up to 0.8°C by mid-May, especially in the northern Sea of Japan. Thereafter, two experiments using a regional atmospheric numerical model are conducted for April and May. One imposes SST synthesized by multiple satellite observations on the lower boundary of the model (the green case). The satellite-derived SST includes influences of biological heating by phytoplankton in the actual ocean. The other uses SST reduced by differences between SSTs computed by the mixed-layer model with and without phytoplankton (the blue case). Under modest wind conditions, extratropical cyclones east and south of the Japan Islands in the blue case develop more rapidly than in the green case. Cyclones are likely initiated by the cool and dry air mass that enhances lower-level baroclinicity above oceanic fronts. This cool and dry air mass is transported from the Sea of Japan, where SST decreases in the absence of phytoplankton. Therefore, incorporating ocean biology is potentially capable of improving regional atmospheric and ocean general circulation models.

The role of the Leeuwin Current and mixed layer depth on the autumn phytoplankton bloom off Ningaloo Reef, Western Australia

2012 ◽  
Vol 32 ◽  
pp. 22-35 ◽  
Author(s):  
Cecile S.G. Rousseaux ◽  
Ryan Lowe ◽  
Ming Feng ◽  
Anya M. Waite ◽  
Peter A. Thompson
Keyword(s):  
Mixed Layer ◽  
Western Australia ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Leeuwin Current ◽  
Ningaloo Reef

Growth of the Euphausiids Thysanoessa inermis, Thysanoessa raschii, and Meganyctiphanes norvegica in a Subarctic Fjord, North Norway

1985 ◽  
Vol 42 (1) ◽  
pp. 14-22 ◽  
Author(s):  
Stig Falk-Petersen
Keyword(s):  
Phytoplankton Bloom ◽  
Dry Weight ◽  
Growth Patterns ◽  
The Body ◽  
Phytoplankton Production ◽  
Final Size ◽  
Spring Phytoplankton Bloom ◽  
Weight Protein ◽  
Meganyctiphanes Norvegica ◽  
The Individual

Growth was studied in terms of the mean carapace length, wet and dry weight, protein, and lipid. Monthly length–weight regressions are presented for a 12-mo period. The growth of Thysanoessa spp. is closely related to phytoplankton production, while Meganyctiphanes norvegica (a carnivore) increases its weight continuously until it reaches its final size. In I-group Thysanoessa the individual maintains its body weight until midwinter, and this is followed by a continuous decrease in the body constituents until the onset of the spring phytoplankton bloom. The growth patterns are correlated with the environmental factors.

scholarly journals Constraining the response of phytoplankton to zooplankton grazing and photo-acclimation in a temperate shelf sea with a 1-D model - towards S2P3 v8.0

2020 ◽  
Author(s):  
Angela A. Bahamondes Dominguez ◽  
Anna E. Hickman ◽  
Robert Marsh ◽  
C. Mark Moore
Keyword(s):  
Phytoplankton Bloom ◽  
Grazing Rate ◽  
Sensitivity Study ◽  
Zooplankton Biomass ◽  
Physiological Parameters ◽  
Spring Phytoplankton Bloom ◽  
Predator Prey ◽  
Shelf Sea ◽  
D Model

Abstract. An established 1-dimensional model of Shelf Sea Physics and Primary Production (S2P3) has been developed into three different new models: S2P3-NPZ which includes a Nutrient-Phytoplankton-Zooplankton (NPZ) framework, where the grazing rate is no longer fixed, but instead varies over time depending on different functions chosen to represent the predator- prey relationship between zooplankton and phytoplankton; S2P3-Photoacclim which includes a representation of the process of photo-acclimation and flexible stoichiometry in phytoplankton; and S2P3 v8.0 which combines the NPZ framework and the variable stoichiometry of phytoplankton at the same time. These model formulations are compared to buoy and CTD observations, as well as zooplankton biomass and in situ phytoplankton physiological parameters obtained in the Central Celtic Sea (CCS). Models were calibrated by comparison to observations of the timing and magnitude of the spring phytoplankton bloom, magnitude of the spring zooplankton bloom, and phytoplankton physiological parameters obtained throughout the water column. A sensitivity study was also performed for each model to understand the effects of individual parameters on model dynamics. Results demonstrate that better agreement with biological observations can be obtained through the addition of representations of photo-acclimation, flexible stoichiometry, and grazing provided these can be adequately constrained.

Impact of a spring phytoplankton bloom on the CO2 system in the mixed layer of the northwestern North Pacific

2002 ◽  
Vol 49 (24-25) ◽  
pp. 5531-5555 ◽  
Author(s):  
A. Murata ◽  
Y. Kumamoto ◽  
C. Saito ◽  
H. Kawakami ◽  
I. Asanuma ◽  
...  
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Phytoplankton Bloom ◽  
Spring Phytoplankton Bloom

scholarly journals Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic

2014 ◽  
Vol 11 (8) ◽  
pp. 12223-12254 ◽  
Author(s):  
K. H. Salmon ◽  
P. Anand ◽  
P. F. Sexton ◽  
M. Conte
Keyword(s):  
Mixed Layer ◽  
North Atlantic ◽  
Community Dynamics ◽  
Phytoplankton Bloom ◽  
North Atlantic Ocean ◽  
Planktonic Foraminifera ◽  
Upper Ocean ◽  
Late Winter ◽  
Planktonic Foraminifer ◽  
Spring Phytoplankton Bloom

Abstract. Oligotrophic regions represent up to 75% of Earth's open-ocean environments, and are typically characterized by nutrient-limited upper-ocean mixed layers. They are thus areas of major importance in understanding the plankton community dynamics and biogeochemical fluxes. Here we present fluxes of total planktonic foraminifera and eleven planktonic foraminifer species from a bi-weekly sediment trap time series in the oligotrophic Sargasso Sea, subtropical western North Atlantic Ocean at 1500 m water depth, over two ∼2.5 year intervals, 1998–2000 and 2007–2010. Foraminifera flux was closely correlated with total mass flux and with carbonate and organic carbon fluxes. We show that the planktonic foraminifera flux increases approximately five-fold during the winter–spring, contributing up to ∼40% of the total carbonate flux, driven primarily by increased fluxes of deeper dwelling ("globorotaliid") species. Interannual variability in total foraminifera flux, and in particular fluxes of the deep dwelling Globorotalia truncatulinoides, Globorotalia hirsuta, Globorotalia inflata, were related to differences in seasonal mixed layer dynamics affecting the strength of the spring phytoplankton bloom and export flux, and by the passage of mesoscale eddies. The heavily calcified, dense carbonate tests of deeper dwelling species (3 times denser than surface dwellers) can contribute up to 90% of the foraminiferal-derived carbonate in this region during late winter-early spring, implying a high seasonality of the biological carbonate pump in oligotrophic oceanic regions. Our data suggest that climate cycles, such as the North Atlantic Oscillation, that modulate the depth of the mixed layer, intensity of nutrient upwelling and primary production could also modulate the strength of the biological carbonate pump in the oligotrophic North Atlantic.

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