Dynamics of the potential photosynthetic activity of marine phytoplankton during illumination change in the North Atlantic

2019 ◽  
pp. 35-45
Author(s):  
Sergey A. Mosharov ◽  
Irina V. Mosharova
Keyword(s):  
Surface Layer ◽  
North Atlantic ◽  
Photosynthetic Activity ◽  
Vertical Mixing ◽  
Experimental Studies ◽  
Marine Phytoplankton ◽  
Light Conditions ◽  
Illumination Change ◽  
The North ◽  
The North Atlantic

The results of experimental studies of the magnitude and rate of variability of the potential photosynthetic activity of marine phytoplankton under variations in light conditions simulating the vertical mixing of phytoplankton within the euphotic layer are considered. It has been shown that photoinhibition of phytoplankton in the surface layer occurs fairly quickly, but is reversible with mixing of water.

scholarly journals Characterization of mixing errors in a coupled physical biogeochemical model of the North Atlantic: implications for nonlinear estimation using Gaussian anamorphosis

Ocean Science ◽  
2010 ◽  
Vol 6 (1) ◽  
pp. 247-262 ◽  
Author(s):  
D. Béal ◽  
P. Brasseur ◽  
J.-M. Brankart ◽  
Y. Ourmières ◽  
J. Verron
Keyword(s):  
North Atlantic ◽  
Chlorophyll Concentration ◽  
Vertical Mixing ◽  
Wind Forcing ◽  
Observation System ◽  
Biogeochemical Model ◽  
Significant Information ◽  
The North ◽  
Biogeochemical Models ◽  
The North Atlantic

Abstract. In biogeochemical models coupled to ocean circulation models, vertical mixing is an important physical process which governs the nutrient supply and the plankton residence in the euphotic layer. However, vertical mixing is often poorly represented in numerical simulations because of approximate parameterizations of sub-grid scale turbulence, wind forcing errors and other mis-represented processes such as restratification by mesoscale eddies. Getting a sufficient knowledge of the nature and structure of these errors is necessary to implement appropriate data assimilation methods and to evaluate if they can be controlled by a given observation system. In this paper, Monte Carlo simulations are conducted to study mixing errors induced by approximate wind forcings in a three-dimensional coupled physical-biogeochemical model of the North Atlantic with a 1/4° horizontal resolution. An ensemble forecast involving 200 members is performed during the 1998 spring bloom, by prescribing perturbations of the wind forcing to generate mixing errors. The biogeochemical response is shown to be rather complex because of nonlinearities and threshold effects in the coupled model. The response of the surface phytoplankton depends on the region of interest and is particularly sensitive to the local stratification. In addition, the statistical relationships computed between the various physical and biogeochemical variables reflect the signature of the non-Gaussian behaviour of the system. It is shown that significant information on the ecosystem can be retrieved from observations of chlorophyll concentration or sea surface temperature if a simple nonlinear change of variables (anamorphosis) is performed by mapping separately and locally the ensemble percentiles of the distributions of each state variable on the Gaussian percentiles. The results of idealized observational updates (performed with perfect observations and neglecting horizontal correlations) indicate that the implementation of this anamorphosis method into sequential assimilation schemes can substantially improve the accuracy of the estimation with respect to classical computations based on the Gaussian assumption.

scholarly journals Spring bloom onset in the Nordic Seas

2016 ◽  
Vol 13 (11) ◽  
pp. 3485-3502 ◽  
Author(s):  
Alexandre Mignot ◽  
Raffaele Ferrari ◽  
Kjell Arne Mork
Keyword(s):  
North Atlantic ◽  
Spring Bloom ◽  
Large Fraction ◽  
Biomass Accumulation ◽  
Marine Phytoplankton ◽  
The Arctic ◽  
Nordic Seas ◽  
In Situ Data ◽  
The North ◽  
The North Atlantic

Abstract. The North Atlantic spring bloom is a massive annual growth event of marine phytoplankton, tiny free-floating algae that form the base of the ocean's food web and generates a large fraction of the global primary production of organic matter. The conditions that trigger the onset of the spring bloom in the Nordic Seas, at the northern edge of the North Atlantic, are studied using in situ data from six bio-optical floats released north of the Arctic Circle. It is often assumed that spring blooms start as soon as phytoplankton cells daily irradiance is sufficiently abundant that division rates exceed losses. The bio-optical float data instead suggest the tantalizing hypothesis that Nordic Seas blooms start when the photoperiod, the number of daily light hours experienced by phytoplankton, exceeds a critical value, independently of division rates. The photoperiod trigger may have developed at high latitudes where photosynthesis is impossible during polar nights and phytoplankton enters into a dormant stage in winter. While the first accumulation of biomass recorded by the bio-optical floats is consistent with the photoperiod hypothesis, it is possible that some biomass accumulation started before the critical photoperiod but at levels too low to be detected by the fluorometers. More precise observations are needed to test the photoperiod hypothesis.

scholarly journals An Analytical Model of the Response of the Meridional Overturning Circulation to Changes in Wind and Buoyancy Forcing

2012 ◽  
Vol 42 (8) ◽  
pp. 1270-1287 ◽  
Author(s):  
Callum J. Shakespeare ◽  
Andrew McC. Hogg
Keyword(s):  
Surface Layer ◽  
Layer Thickness ◽  
Analytical Model ◽  
Wind Stress ◽  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
The North ◽  
The North Atlantic ◽  
Surface Buoyancy ◽  
Surface Layer Thickness

Abstract An analytical model of the full-depth ocean stratification and meridional overturning circulation for an idealized Atlantic basin with a circumpolar channel is presented. The model explicitly describes the ocean response to both Southern Ocean winds and the global pattern and strength of prescribed surface buoyancy fluxes. The construction of three layers, defined by the two isopycnals of overturning extrema, allows the description of circulation and stratification in both the upper and abyssal ocean. The system is fully solved in the adiabatic limit to yield scales for the surface layer thickness, buoyancies of each layer, and overturning magnitudes. The analytical model also allows scaling of the Antarctic Circumpolar Current (ACC) transport. The veracity of the three-layer framework and derived scales is confirmed by applying the analytical model to an idealized geometry, eddy-permitting ocean general circulation model. Consistent with previous results, the abyssal overturning is found to scale inversely with wind stress, whereas the North Atlantic overturning and surface-layer thickness scale linearly with wind stress. In terms of the prescribed surface buoyancy fluxes, increased negative fluxes (buoyancy removal) in the North Atlantic increase the North Atlantic overturning and surface-layer thickness, whereas increased positive fluxes in the middle and low latitudes lead to a decrease in both parameters. Increased negative surface buoyancy fluxes to the south of Drake Passage increase the abyssal overturning and reduce the abyssal buoyancy. The ACC transport scales to first order with the sum of the Ekman transport and the abyssal overturning and thus increases with both wind stress and southern surface buoyancy flux magnitude.

Description of a New Species of Oligobrachia (Pogonophora) from the North Atlantic, With a Survey of the Oligobrachiidae

1978 ◽  
Vol 58 (2) ◽  
pp. 357-365 ◽  
Author(s):  
Eve C. Southward
Keyword(s):  
New Species ◽  
Continental Slope ◽  
North Atlantic ◽  
Rare Species ◽  
Experimental Studies ◽  
Bay Of Biscay ◽  
The North ◽  
The Family ◽  
The North Atlantic ◽  
A New Species

Collections of bottom-living animals from the continental slope of the northern Bay of Biscay contain a new species of Oligobrachia; this increases the number of species of Oligobrachia known from the North Atlantic to five. Oligobrachiids are quite frequently found incubating embryos and five individuals of the new species carry embryos. Oligobrachia embryos have been studied morphologically already (Ivanov, 1957, 1975; Southward & Southward, 1963; Brattegard, 1966; Ivanov & Gureeva, 1976) and should prove useful material for experimental studies in future. Incubation is also known in the family Siboglinidae, but neither embryos nor larvae have been seen in any other pogonophoran families. The Biscay collections also contain additional specimens of Oligobrachia ivanovi and these have been useful in revising the description of this rather rare species.

scholarly journals Lithological and biogeochemical investigations of the North Atlantic sediment system (data from the 49th cruise of the R/V Akademik Ioffe)

2019 ◽  
Vol 59 (4) ◽  
pp. 641-655
Author(s):  
E. A. Novichkova ◽  
A. S. Savvichev ◽  
L. D. Bashirova ◽  
N. V. Kozina ◽  
A. A. Klyuvitkin ◽  
...  
Keyword(s):  
North Atlantic ◽  
General Pattern ◽  
Sediment Supply ◽  
Marine Phytoplankton ◽  
Middle Pleistocene ◽  
The North ◽  
Suspended Particulate ◽  
49Th Cruise ◽  
System Data ◽  
The North Atlantic

Marine sediments and samples of suspended particulate matter from the North Atlantic were studied. It is shown that modern sedimentation in this area is controlled mainly by the efficiency of autochthonous marine phytoplankton and sediment supply by the system of near-bottom currents, as well as by means of the ice-rafting. The studied sediment sections were formed in the North Atlantic during the Middle Pleistocene to Holocene. The highest sedimentation rate, up to 58.3 cm/kyr, is established for AI-3359 core, collected in the area of the Gardar and Björn Drifts. This makes the core very interesting for detailed paleoreconstructions. AI-3378 and AI-3415 cores are characterized by low sedimentation rates. Nevertheless, they are of interest for spatial paleoreconstructions on a continuous timeline. The general pattern is established for the first time for the sediments from the central North Atlantic: biogeochemically significant processes are detected only in the thin surface layer (0–2 cm) and almost completely cease at depths of 90–180 cm. The processes are probably controlled by the position of the sampling stations and the composition of organic matter (OM) but not related to the age of the sedimentary layer. The low microbial activity in the sediments is most likely the result of a lack of OM.

scholarly journals Heme b in marine phytoplankton and particulate material from the North Atlantic Ocean

2013 ◽  
Vol 483 ◽  
pp. 1-17 ◽  
Author(s):  
DJ Honey ◽  
M Gledhill ◽  
TS Bibby ◽  
FE Legiret ◽  
NJ Pratt ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Particulate Material ◽  
Marine Phytoplankton ◽  
The North ◽  
The North Atlantic
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