scholarly journals Model study of nutrient and phytoplankton dynamics in the Gulf of Maine: patterns and drivers for seasonal and interannual variability

2014 ◽  
Vol 72 (2) ◽  
pp. 388-402 ◽  
Author(s):  
Rucheng Tian ◽  
Changsheng Chen ◽  
Jianhua Qi ◽  
Rubao Ji ◽  
Robert C. Beardsley ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Gulf Of Maine ◽  
Phytoplankton Bloom ◽  
Function Analysis ◽  
Nutrient Supply ◽  
Open Boundary ◽  
Phytoplankton Production ◽  
Phytoplankton Dynamics ◽  
Salinity Regime ◽  
Dominant Feature

Abstract Coupled physical–biological modelling experiments were made for the period of 1995–2009 to analyse the spatial and interannual variability of nutrients and phytoplankton production in the Gulf of Maine (GOM). The physical model was the Finite-Volume Community Ocean Model (FVCOM) and the biological model was a Nitrogen, Phytoplankton, Zooplankton, and Detritus (NPZD) model. The simulation was carried out with realistic meteorological surface forcing, five major tidal constituents, river discharge, and observation-based open boundary conditions. The results were robust with comparison to SeaWiFS chlorophyll data and historical data of nitrogen. An Empirical Orthogonal Function analysis clearly identified two dominant modes in nutrient and phytoplankton dynamics: (1) sustained nutrient supply and phytoplankton production from spring through autumn, and (2) a dominating phytoplankton bloom in spring, relatively low production in summer, and a noticeable bloom in autumn. Mode 1 was a dominant feature in strong tidal energy dissipation regions such as the southwestern shelf of Nova Scotia, Georges Bank, Nantucket Shoals, the Bay of Fundy, and the coastal regions of GOM, where tidal pumping and mixing were the major drivers for the sustained nutrient supply, and primary production showed certain resilience with less interannual variability. Mode 2 was a characteristic in the deep Gulf, the offshore region of the Scotian Shelf, and in the open sea area, where the timing and amplitude of the spring phytoplankton bloom is essentially controlled by the salinity regime, and its interannual variability was significantly influenced by freshening events controlled by local and remote forcing.

scholarly journals Modeling the influence of low-salinity water inflow on winter-spring phytoplankton dynamics in the Nova Scotian Shelf–Gulf of Maine region

2008 ◽  
Vol 30 (12) ◽  
pp. 1399-1416 ◽  
Author(s):  
Rubao Ji ◽  
Cabell S. Davis ◽  
Changsheng Chen ◽  
David W. Townsend ◽  
David G. Mountain ◽  
...  
Keyword(s):  
Gulf Of Maine ◽  
Water Inflow ◽  
Phytoplankton Dynamics ◽  
Scotian Shelf ◽  
Low Salinity ◽  
Low Salinity Water ◽  
Salinity Water ◽  
Nova Scotian

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 Seasonal and interannual variability of physical and biological dynamics at the Shelfbreak Front of the Middle Atlantic Bight: nutrient supply mechanisms

2011 ◽  
Vol 8 (1) ◽  
pp. 1555-1590 ◽  
Author(s):  
R. He ◽  
K. Chen ◽  
K. Fennel ◽  
G. G. Gawarkiewicz ◽  
Keyword(s):  
Interannual Variability ◽  
Water Column ◽  
Circulation Model ◽  
Deep Ocean ◽  
Nutrient Supply ◽  
Early Summer ◽  
Late Winter ◽  
Middle Atlantic Bight ◽  
Seasonal And Interannual Variability ◽  
Middle Atlantic

Abstract. A size-structured ecosystem model is coupled to a 3-dimensional, high-resolution circulation model to investigate the seasonal and interannual variability of physical and biological states and their driving mechanisms at the shelfbreak front of the Middle Atlantic Bight (MAB). Simulated surface chlorophyll fields compare favorably to the satellite observations and capture the shelfbreak biomass enhancement, which is one of the essential biological features of the region. The domain-wide upper water column nutrient content peaks in late winter-early spring. The phytoplankton spring bloom starts 1–2 months later, followed by a zooplankton bloom in early summer. Seasonal and interannual variability in hindcast shelfbreak nutrient supply is controlled by three processes: (1) local mixing that deepens the mixed layer and injects deep ocean nutrients into the upper water column; (2) alongshore nutrient transport by the shelfbreak jet and associated currents; and (3) nutrient upwelling associated with shelfbreak bottom boundary layer convergence. Interannual variability of physical and biological processes are highlighted by cross-shelf nutrient budget diagnostics for spring 2004 and 2007, which show not only complex vertical structure of various dynamical terms, but also significant variations in magnitude between the two years.

scholarly journals Regional-scale phytoplankton dynamics and their association with glacier meltwater runoff in Svalbard

2021 ◽  
Author(s):  
Thorben Dunse ◽  
Kaixing Dong ◽  
Kjetil Schanke Aas ◽  
Leif Christian Stige
Keyword(s):  
Sea Ice ◽  
Chlorophyll A ◽  
Freshwater Discharge ◽  
The Arctic ◽  
Phytoplankton Production ◽  
Phytoplankton Dynamics ◽  
Glacier Meltwater ◽  
Meltwater Runoff ◽  
Glacier Runoff

Abstract. Arctic amplification of global warming has accelerated mass loss of Arctic land ice over the past decades and lead to increased freshwater discharge into glacier fjords and adjacent seas. Glacier freshwater discharge is typically associated with high sediment loads which limits the euphotic depth, but may also provide surface waters with essential nutrients, thus having counter-acting effects on marine productivity. In-situ observations from a few measured fjords across the Arctic indicate that glacier fjords dominated by marine-terminating glaciers are typically more productive than those with only land-terminating glaciers. Here we combine chlorophyll a from satellite ocean colour, an indicator of phytoplankton biomass, with glacier meltwater runoff from climatic mass-balance modelling to establish a statistical model of summertime-phytoplankton dynamics in Svalbard (mid-June to September). Statistical analysis reveals positive spatiotemporal association of chlorophyll a with glacier runoff for 7 out of 14 primary hydrological regions. These regions consist predominantly of the major fjord systems of Svalbard. The adjacent land areas are characterized by a wide range of total glacier coverage (35.5 % to 81.2 %) and fraction of marine-terminating glacier area (40.2 % to 87.4 %). We find that an increase in specific glacier-runoff rate of 10 mm water equivalent per 8-day timeperiod raises summertime chlorophyll a concentrations by 5.2 % to 20.0 %, depending on region. During the annual peak discharge we estimate that glacier runoff contributes to 13.1 % to 50.2 % increase in chlorophyll a compared to situations with no runoff. This suggest that glacier runoff is an important factor sustaining summertime phytoplankton production in Svalbard fjords, in line with findings from several fjords in Greenland. In contrast, for regions bordering open coasts, and beyond 10 km distance from the shore, we do not find significant association of chlorophyll a with runoff. In these regions, physical ocean and sea ice variables control chlorophyll a, pointing at the importance of a late sea ice breakup in northern Svalbard, as well as the advection of Atlantic water masses along the West Spitsbergen Current for summertime phytoplankton dynamics. Our method allows for investigation and monitoring of glacier-runoff effects on primary production throughout the summer season and is applicable on a Pan-Arctic scale, thus complementing valuable but scarce in-situ measurements in both space and time.

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.

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