scholarly journals Direct contribution of phytoplankton-sized particles to optical backscattering in the open ocean

2009 ◽  
Vol 6 (1) ◽  
pp. 291-340 ◽  
Author(s):  
G. Dall'Olmo ◽  
T. K. Westberry ◽  
M. J. Behrenfeld ◽  
E. Boss ◽  
W. H. Slade
Keyword(s):  
Optical Properties ◽  
Surface Waters ◽  
Phytoplankton Biomass ◽  
Field Studies ◽  
Open Ocean ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Similar Information ◽  
The Relationship ◽  
Beam Attenuation Coefficient

Abstract. Light scattering properties of oceanic particles have been suggested as an alternative index of phytoplankton biomass than chlorophyll-a concentration (chl-a), with the benefit of being less sensitive to physiological forcings (e.g., light and nutrients) that alter the intracellular pigment concentrations. The drawback of particulate scattering is that it is not unique to phytoplankton. Nevertheless, field studies have demonstrated that, to first order, the particulate beam-attenuation coefficient (cp) can track phytoplankton abundance. The relationship between cp and the particulate backscattering coefficient (bbp), a property retrievable from space, has not been fully evaluated, largely due to a lack of open-ocean field observations. Here, we present extensive data on inherent optical properties from the Equatorial Pacific surface waters and demonstrate a remarkable coherence in bbp and cp. Coincident measurements of particle size distributions (PSDs) and optical properties of size-fractionated samples indicate that this covariance is due to both the conserved nature of the PSD and a greater contribution of phytoplankton-sized particles to bbp than theoretically predicted. These findings suggest that satellite-derived bbp could provide similar information on phytoplankton biomass in the open ocean as cp.

scholarly journals Significant contribution of large particles to optical backscattering in the open ocean

2009 ◽  
Vol 6 (6) ◽  
pp. 947-967 ◽  
Author(s):  
G. Dall'Olmo ◽  
T. K. Westberry ◽  
M. J. Behrenfeld ◽  
E. Boss ◽  
W. H. Slade
Keyword(s):  
Optical Properties ◽  
Phytoplankton Biomass ◽  
Field Studies ◽  
Open Ocean ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Large Particles ◽  
Similar Information ◽  
The Relationship ◽  
Beam Attenuation Coefficient

Abstract. The light scattering properties of oceanic particles have been suggested as an alternative index of phytoplankton biomass than chlorophyll-a concentration (chl-a), with the benefit of being less sensitive to physiological forcings (e.g., light and nutrients) that alter the intracellular pigment concentrations. The drawback of particulate scattering is that it is not unique to phytoplankton. Nevertheless, field studies have demonstrated that, to first order, the particulate beam-attenuation coefficient (cp) can track phytoplankton biomass. The relationship between cp and the particulate backscattering coefficient (bbp), a property retrievable from space, has not been fully evaluated, largely due to a lack of open-ocean field observations. Here, we present extensive data on inherent optical properties from the Equatorial Pacific surface waters and demonstrate a remarkable coherence in bbp and cp. Coincident measurements of particle size distributions (PSDs) and optical properties of size-fractionated samples indicate that this covariance is due to both the conserved nature of the PSD and a greater contribution of phytoplankton-sized particles to bbp than theoretically predicted. These findings suggest that satellite-derived bbpcould provide similar information on phytoplankton biomass in the open ocean as cp.

scholarly journals Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of <i>Microcystis aeruginosa</i>

2013 ◽  
Vol 10 (12) ◽  
pp. 8139-8157 ◽  
Author(s):  
M. W. Matthews ◽  
S. Bernard
Keyword(s):  
Optical Properties ◽  
Microcystis Aeruginosa ◽  
Cyanobacterial Blooms ◽  
Shell Layer ◽  
Sphere Model ◽  
Homogeneous Population ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Impact

Abstract. A two-layered sphere model is used to investigate the impact of gas vacuoles on the inherent optical properties (IOPs) of the cyanophyte Microcystis aeruginosa. Enclosing a vacuole-like particle within a chromatoplasm shell layer significantly altered spectral scattering and increased backscattering. The two-layered sphere model reproduced features in the spectral attenuation and volume scattering function (VSF) that have previously been attributed to gas vacuoles. This suggests the model is good at least as a first approximation for investigating how gas vacuoles alter the IOPs. Measured Rrs was used to provide a range of values for the central value of the real refractive index, 1 + ε, for the shell layer using measured IOPs and a radiative transfer model. Sufficient optical closure was obtained for 1 + ε between 1.1 and 1.14, which had corresponding Chl a-specific phytoplankton backscattering, bbφ*, between 3.9 and 7.2 × 10−3 m2 mg−1 at 510 nm. The bbφ* values are in close agreement with the literature and in situ particulate backscattering measurements. Rrs simulated for a population of vacuolate cells was greatly enlarged relative to a homogeneous population. A sensitivity analysis of empirical algorithms for estimating Chl a in eutrophic/hypertrophic waters suggests these are robust under variable constituent concentrations and likely to be species-sensitive. The study confirms that gas vacuoles cause significant increase in backscattering and are responsible for the high Rrs values observed in buoyant cyanobacterial blooms. Gas vacuoles are therefore one of the most important bio-optical substructures influencing the IOPs in phytoplankton.

scholarly journals Effect of sea‐ice melt on inherent optical properties and vertical distribution of solar radiant heating in Arctic surface waters

2015 ◽  
Vol 120 (10) ◽  
pp. 7028-7039 ◽  
Author(s):  
Mats A. Granskog ◽  
Alexey K. Pavlov ◽  
Sławomir Sagan ◽  
Piotr Kowalczuk ◽  
Anna Raczkowska ◽  
...  
Keyword(s):  
Optical Properties ◽  
Sea Ice ◽  
Vertical Distribution ◽  
Surface Waters ◽  
Radiant Heating ◽  
Ice Melt ◽  
Inherent Optical Properties ◽  
Arctic Surface

scholarly journals Effects of nitrate and phosphate supply on chromophoric and fluorescent dissolved organic matter in the Eastern Tropical North Atlantic: a mesocosm study

2015 ◽  
Vol 12 (10) ◽  
pp. 7209-7255
Author(s):  
A. N. Loginova ◽  
C. Borchard ◽  
J. Meyer ◽  
H. Hauss ◽  
R. Kiko ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Optical Properties ◽  
Amino Acid ◽  
Dissolved Organic Matter ◽  
North Atlantic ◽  
Phytoplankton Biomass ◽  
Open Ocean ◽  
Nutrient Concentrations ◽  
Tropical North Atlantic

Abstract. The Eastern Tropical North Atlantic (ETNA) is an open ocean region with little input of terrestrial dissolved organic matter (DOM), suggesting that pelagic production has to be the main source of DOM. Inorganic nitrogen (DIN) and phosphorus (DIP) concentrations affect pelagic production, leading to DOM modifications. The quantitative and qualitative changes in DOM are often estimated by its optical properties. Colored DOM (CDOM) is often used to estimate dissolved organic carbon (DOC) concentrations by applied techniques, e.g. through remote sensing, whereas DOM properties, such as molecular weight, can be estimated from the slopes of the CDOM absorption spectra (S). Fluorescence properties of CDOM (FDOM) allow discriminating between different structural CDOM properties. The investigation of distribution and cycling of CDOM and FDOM was recognized to be important for understanding of physical and biogeochemical processes, influencing DOM. However, little information is available about effects of nutrient variability on CDOM and FDOM dynamics. Here we present results from two mesocosm experiments conducted with a natural plankton community of the ETNA, where effects of DIP ("Varied P") and DIN ("Varied N") supply on optical properties of DOM were studied. CDOM accumulated proportionally to phytoplankton biomass during the experiments. S decreased over time indicating accumulation of high molecular weight DOM. In Varied N, an additional CDOM portion, as a result of bacterial DOM reworking, was determined. It increased the CDOM fraction in DOC proportionally to the supplied DIN. The humic-like FDOM component (Comp.1) was derived by bacteria proportionally to DIN supply. The bound-to-protein amino acid-like FDOM component (Comp.2) was released irrespectively to phytoplankton biomass, but depending on DIP and DIN concentrations, as a part of an overflow mechanism. Under high DIN supply, Comp.2 was removed by bacterial reworking processes, leading to an accumulation of humic-like Comp.1. No influence of nutrient availability on amino acid-like FDOM component in peptide form (Comp.3) was observed. Comp.3 potentially acted as an intermediate product during formation or degradation Comp.2. Our findings suggest that changes in nutrient concentrations may lead to substantial responses in the quantity and "quality" of optically active DOM and, therefore, might bias results of the applied techniques for an estimation of DOC concentrations in open ocean regions.

Optical Effects of Large Particles

Ocean Optics ◽  
1994 ◽  
Author(s):  
Kendall L. Carder ◽  
David K. Costello
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Process Model ◽  
Light Field ◽  
Ocean Optics ◽  
Backscattering Coefficient ◽  
Model Inversion ◽  
Inherent Optical Properties ◽  
And Inversion ◽  
The Relationship

Two important problems facing the ocean optics research community in the coming decade concern optical model closure and inversion (see Chapter 3). We obtain model closure if we can describe the measured light environment by combining elementary measurements of the optical properties of the medium with radiative transfer theory. If we can accurately deduce the concentration of various constituents from a combination of measures of the submarine light field and inverse model calculations, we term this process model inversion. The most elementary measurements of the optical properties of the sea are those that are independent of the geometry of the light field, the inherent optical properties (Preisendorfer, 1961). Optical properties that are dependent on the geometry of the light field are termed apparent optical properties (AOP). Models of the submarine light field typically relate apparent optical properties to inherent optical properties (see Chapter 2). Examples include the relationship between the AOP irradiance reflectance R and a combination of inherent optical properties (backscattering coefficient bb and absorption coefficient a), and the relationship between the AOP downwelling diffuse attenuation coefficient kd and a combination of the absorption coefficient, backscattering coefficient, and downwelling average cosine μd (e.g., Gordon et al., 1975; Morel and Prieur, 1977; Smith and Baker, 1981; Morel, 1988; Kirk, 1984a). Under some circumstances these relationships work well enough that the absorption coefficient can be derived indirectly. This is important since measurement of the absorption coefficient by direct means has been difficult. Derived values for the absorption coefficient by model inversion methods are not easily verified by independent measurements, however, because of the difficulty of measuring the absorption coefficient. Model closure and model inversion both become more tenuous when the following phenomena are present: 1. Transpectral or inelastic scattering such as fluorescence (e.g., Gordon, 1979; Carder and Steward, 1985; Mitchell and Kiefer, 1988a; Spitzer and Dirks, 1985; Hawes and Carder, 1990) or water Raman scattering (Marshall and Smith, 1990; Stavn, 1990; Stavn and Weidemann, 1988a,b; Peacock et al, 1990; Chapter 12 this volume). 2. Particles that are large relative to the measurement volume for inherent optical property meters such as beam transmissometers, light-scattering photometers, fluorometers, and absorption meters.

Optical Closure: from Theory to Measurement

Ocean Optics ◽  
1994 ◽  
Author(s):  
J. Ronald V. Zaneveld
Keyword(s):  
Optical Properties ◽  
Light Field ◽  
Vertical Structure ◽  
Spectral Radiance ◽  
Major Influence ◽  
The Sun ◽  
Attenuation Coefficients ◽  
Inherent Optical Properties ◽  
Dissolved Matter ◽  
Beam Attenuation Coefficient

The intensity and spectrum of the light in the ocean have a major influence on the biological processes. These processes in turn determine the concentrations of much of the suspended and dissolved matter in the ocean, which affect the way in which the light is scattered and absorbed. These relationships can perhaps be most easily illustrated schematically as in Fig. 3-1. At the upper boundary we have the sun and sky radiances and the surface transmission conditions that combine to provide the energy entering through the surface. The ocean itself contains the vertical structure of those optical properties that do not depend on the structure of the light field, but depend only on the properties of the suspended and dissolved materials: the absorption coefficient a(λ,z), the beam attenuation coefficient c(λ,z), and the volume scattering function β(θ,λ,z). These are known as inherent optical properties, because they do not depend on the source radiance field (Preisendorfer, 1976). They are a function only of the suspended and dissolved materials in the water, and of the water itself. How does the vertical structure of the inherent optical properties affect the vertical structure of the radiance field in the ocean itself? This is the problem of radiative transfer in which we try to predict the intensity, direction, and spectrum of the light (spectral radiance) in the ocean, based on a set of given inherent optical properties. Those properties of the light field in the ocean that depend on the radiance are known as the apparent optical properties. Radiance field integrals, such as the vector irradiance, E(λ,z), the scalar irradiance E0(λ,z), and their attenuation coefficients are also apparent optical properties.

scholarly journals Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of <i>M. aeruginosa</i>

2013 ◽  
Vol 10 (6) ◽  
pp. 10531-10579 ◽  
Author(s):  
M. W. Matthews ◽  
S. Bernard
Keyword(s):  
Optical Properties ◽  
Cyanobacterial Blooms ◽  
Transfer Model ◽  
Shell Layer ◽  
Sphere Model ◽  
Homogeneous Population ◽  
Chl A ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Impact

Abstract. A two-layered sphere model is used to investigate the impact of gas vacuoles on the inherent optical properties (IOPs) of the cyanophyte Microcystis aeruginosa. Enclosing a vacuole–like particle within a chromatoplasm shell layer significantly altered spectral scattering and increased backscattering. The two-layered sphere model reproduced features in the spectral attenuation and volume scattering function (VSF) that have previously been attributed to gas vacuoles. This suggests the model is good at least as a first approximation for investigating how gas vacuoles alter the IOPs. The central value of the real refractive index, 1+ ε, for the shell layer was determined using a radiative transfer model and measured remote sensing reflectance, Rrs, and IOP data. For a cell with 50% vacuole volume, the mean 1+ ε value for the shell layer was 1.12. The corresponding chl a specific phytoplankton backscattering coefficient, bbφ&amp;ast;, ranged between 3.9 × 10−3 and 7.2 × 10−3 m2 mg−1 at 510 nm. This agrees closely with in situ particulate backscattering measurements and values reported elsewhere. Rrs simulated for a population of vacuolate cells was greatly enlarged relative to a homogeneous population. Empirical algorithms based on Rrs were derived for estimating chl a in eutrophic/hypertrophic waters dominated by M. aeruginosa. The study confirms that gas vacuoles cause significant increase in backscattering and are responsible for the high Rrs values observed in buoyant cyanobacterial blooms. Gas vacuoles are therefore one of the most important bio-optical substructures influencing the IOPs in phytoplankton.

scholarly journals Biological and oceanographic upwelling indicators at Cabo Frio (RJ)

1997 ◽  
Vol 45 (1-2) ◽  
pp. 11-23 ◽  
Author(s):  
Gleyci A. O. Moser ◽  
Sônia M. F. Gianesella-Galvão
Keyword(s):  
Surface Waters ◽  
Phytoplankton Biomass ◽  
High Surface ◽  
Principal Component ◽  
Chemical Parameters ◽  
Chl A ◽  
South Atlantic Central Water ◽  
Winter Time ◽  
Upwelling Event ◽  
Cabo Frio

Phytoplankton biomass, chemical parameters and hydrology were studied in a transect 101.6 km long off Cabo Frio (RJ), Southeast Brazil, during summer (December 29 to 31, 1991) and winter (June 27 to 30, 1992). Wind induced upwelling events are frequently observed in the area during summer, becoming rare during winter. By the summer cruise a bloom of phytoplankton was observed in surface, close to the coast, with chlorophyll concentrations reaching 25.55 mg Chl-a m-3, uncoupled from the cold, nutrient rich waters of South Atlantic Central Water (SACW), found below 40 m depth. During the winter cruise, the SACW raised at the surface waters in front of Cabo Frio depicting an upwelling event. However, in spite of high surface nitrate concentrations (up to 7.7 f.1M) chlorophyll-a were lower than 2 mg Chl-a m-3. The phytoplankton biomass, meteorological and hydrological data suggest a probable upwelling event immediately before the summer cruise, and an ongoing one during winter time. Cluster analyses and principal component analyses (PCA) were applied to summer and winter data, pointing out multidimensional fronts in the area during both seasons.

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