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

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.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f89-288 ◽

1989 ◽

Vol 46 (S1) ◽

pp. s183-s199 ◽

Cited By ~ 6

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.

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

Journal of Climate ◽

10.1175/jcli-d-14-00277.1 ◽

2014 ◽

Vol 27 (20) ◽

pp. 7587-7602 ◽

Cited By ~ 1

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.

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The Advent of the Spring Bloom in the Eastern Subarctic Pacific Ocean

Journal of the Fisheries Research Board of Canada ◽

10.1139/f66-045 ◽

1966 ◽

Vol 23 (4) ◽

pp. 539-546 ◽

Cited By ~ 26

Author(s):

T. R. Parsons ◽

L. F. Giovando ◽

R. J. LeBrasseur

Keyword(s):

Pacific Ocean ◽

Primary Production ◽

Mixed Layer ◽

Spring Bloom ◽

Phytoplankton Bloom ◽

Central Area ◽

Critical Depth ◽

Spring Phytoplankton Bloom ◽

Subarctic Pacific ◽

Subarctic Pacific Ocean

The spring phytoplankton bloom in the eastern subarctic Pacific Ocean was described from estimations of the critical depth and the depth of the mixed layer. The results suggested that the spring bloom begins during February in the area south of 45°N and east of 135°W. During March the bloom area advances in a northwesterly direction to 50°N at 125°W and 45°N at 135°W. A net increase in primary production is also possible during March near 55°N and 155°W. During April, the spring bloom is generally well established throughout the region except in a central area where suitable conditions are not firmly established until May. This description is supported by the distribution of copepods in the region during April.

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Characterizing upper-ocean mixing and its effect on the spring phytoplankton bloom with in situ data

ICES Journal of Marine Science ◽

10.1093/icesjms/fsv006 ◽

2015 ◽

Vol 72 (6) ◽

pp. 1961-1970 ◽

Cited By ~ 12

Author(s):

Sarah R. Brody ◽

M. Susan Lozier

Keyword(s):

Mixed Layer ◽

Spring Bloom ◽

Phytoplankton Bloom ◽

Upper Ocean ◽

Late Winter ◽

Uniform Density ◽

Spring Phytoplankton Bloom ◽

In Situ Data ◽

Active Mixing

Abstract Since publication, the Sverdrup hypothesis, that phytoplankton are uniformly distributed within the ocean mixed layer and bloom once the ocean warms and stratifies in spring, has been the conventional explanation of subpolar phytoplankton spring bloom initiation. Recent studies have sought to differentiate between the actively mixing section of the upper ocean and the uniform-density mixed layer, arguing, as Sverdrup implied, that decreases in active mixing drive the spring bloom. In this study, we use in situ data to investigate the characteristics and depth of active mixing in both buoyancy- and wind-driven regimes and explore the idea that the shift from buoyancy-driven to wind-driven mixing in the late winter or early spring creates the conditions necessary for blooms to begin. We identify the bloom initiation based on net rates of biomass accumulation and relate changes in the depth of active mixing to changes in biomass depth profiles. These analyses support the idea that decreases in the depth of active mixing, a result of the transition from buoyancy-driven to wind-driven mixing, control the timing of the spring bloom.

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

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1421576112 ◽

2014 ◽

Vol 112 (1) ◽

pp. E15-E20 ◽

Cited By ~ 33

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.

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