Optical properties of Gas-vacuolate cells and colonies of Microcystis in relation to light Attenuation in a Turbid, Stratified Reservoir (Mount Bold Reservoir, South Australia)

1989 ◽  
Vol 40 (6) ◽  
pp. 595 ◽  
Author(s):  
GG Ganf ◽  
RL Oliver ◽  
AE Walsby
Keyword(s):  
Optical Properties ◽  
Light Attenuation ◽  
Significant Proportion ◽  
Spectral Composition ◽  
General Rule ◽  
Slight Modification ◽  
Scattering Coefficient ◽  
Inherent Optical Properties ◽  
Gas Vacuoles ◽  
The Relationship

Profiles of downwelling and upwelling irradiance were measured in a stratified, turbid reservoir, when Microcystis aeruginosa formed a significant proportion of the phytoplankton community. The attenuation coefficient (Kd) was c. 2.1 m-1 and the reflectance (R) c. 0.03. Application of Kirk's simulation model relating apparent and inherent optical properties enabled calculation of coefficients of absorption (a; 1.3-1.6 m-') and scattering (6; 5-7 m-1). The asymptotic diffuse backscattering coefficient (0.2 m-1) was derived from the relationship b′b = 3.6 RaKd, a slight modification of Kirk's original equation. Turbidity measurements supported the general rule that nephelometric turbidity was numerically equivalent to the scattering coefficient. There was good agreement between the measured light profile and one reconstructed from inherent optical properties using the relationship between Kd, a and b. The optical properties of cells and colonies of Microcystis were investigated before and after the collapse of gas vacuoles. The Chla-specific absorption coefficient for cells (0.0138 m2 mg,-1 Chla) was higher than for colonies (0.0106 m2 mg,-1 Chla) at a depth equivalent to 0.2 m. Both coefficients decreased with increasing depth as the spectral composition changed. The Chla-specific scattering coefficient for vacuolate cells (0.14 m2 mg,-1 Chla) was greater than for colonies (0.11 m2 mg,-1 Chla), and a similar correspondence occurred for non-vacuolate cells and colonies (0.029 and 0.020 m2 mg,-1 Chla respectively). These measurements illustrate the package effect and also that c. 80% of light scattering is due to gas vacuoles. The relationship between pressure-sensitive turbidity and gas-vacuole volume suggested that 1 gL mL-1 was equivalent to a turbidity of 2 NTU. These optical characteristics, combined with the buoyant nature of Microcystis, suggest that it is a canopy species.

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.

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.

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 Development of a Diffuse Reflectance Probe for In Situ Measurement of Inherent Optical Properties in Sea Ice

2021 ◽  
Author(s):  
Christophe Perron ◽  
Christian Katlein ◽  
Simon Lambert-Girard ◽  
Edouard Leymarie ◽  
Louis-Philippe Guinard ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Optical Properties ◽  
Sea Ice ◽  
Phase Function ◽  
Diffuse Reflectance ◽  
Scattering Coefficient ◽  
Scattering Medium ◽  
Inherent Optical Properties ◽  
Reduced Scattering Coefficient

Abstract. Detailed characterization of the spatially and temporally varying inherent optical properties (IOPs) of sea ice is necessary to better predict energy and mass balances, as well as ice-associated primary production. Here we present the development of an active optical probe to measure IOPs of a small volume of sea ice (dm3) in situ and non-destructively. The probe is derived from the diffuse reflectance method used to measure the IOPs of human tissues. The instrument emits light into the ice by the use of optical fibre. Backscattered light is measured at multiple distances away from the source using several receiving fibres. Comparison to a Monte Carlo simulated lookup table allows to retrieve the absorption coefficient, the reduced scattering coefficient and a phase function similarity parameter γ, introduced by Bevilacqua and Depeursinge (1999), depending on the two first moments of the Legendre polynomials, allowing to analyze the backscattered light not satisfying the diffusion regime. Monte Carlo simulations showed that the depth cumulating 95% of the signal is between 40±2 mm and 270±20 mm depending on the source-detector distance and on the ice scattering properties. The magnitude of the instrument validation error on the reduced scattering coefficient ranged from 0.07% for the most scattering medium to 35% for the less scattering medium over the two orders of magnitude we validated. Vertical profiles of the reduced scattering coefficient were obtained with decimeter resolution on first-year Arctic interior sea ice on Baffin Island in early spring 2019. We measured values of up to 7.1 m−1 for the uppermost layer of interior ice and down to 0.15±0.05 m−1 for the bottommost layer. These values are in the range of polar interior sea ice measurements published by other authors. The inversion of the reduced scattering coefficient at this scale was strongly dependent of γ, highlighting the need to define the higher moments of the phase function. This novel developed probe provides a fast and reliable means for measurement of scattering into sea ice.

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.

Optical Properties of Water Body in Xiaojiang River Backwater Area, Three Gorges Reservoir, 2008

2010 ◽  
Vol 113-116 ◽  
pp. 840-846
Author(s):  
Fang Fang ◽  
Hong Zhou ◽  
Jing Song Guo ◽  
Zhe Li ◽  
Yong Bo Chen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Water Body ◽  
Three Gorges Reservoir ◽  
Light Attenuation ◽  
Particulate Matters ◽  
Three Gorges ◽  
Strong Correlations ◽  
Secchi Disc ◽  
The Impact ◽  
The Relationship

To discuss optical properties of water body in Xiaojiang river backwater area after the early impounding stage of the Three Gorges Reservoir (TGR), the correlations between visible light attenuation coefficients (Kd(PAR)) and Secchi Disc transparency (SD), total particulate matters (TPM), dissolved organic carbon (DOC) and chlorophyll-a (Chla) were investigated, and spatiotemporal variations of Kd(PAR) and its influencing factors were analyzed. In the study area, there are no significant spatial variations of Kd(PAR), but the seasonal changes are obvious, with the highest value in winter and the lowest value in summer. Statistics analysis suggests that there are strong correlations between Kd(PAR) and SD, TPM, TIM, the value of R2 are 0.7791, 0.7285, and 0.7637, respectively. The relationship between Kd(PAR) and DOC is less significant(R2=0.1289). However, the correlation between Kd(PAR) and Chla was weak (R2=0.006). Further study shows that, the impact of total particulate matters on the optical properties of water body is as a result of both seasonal impoundment of the TGR and particular hydrological condition of Xiaojiang river basin.

scholarly journals Photosynthesis and Bio-Optical Properties of Fluorescent Mesophotic Corals

2021 ◽  
Vol 8 ◽  
Author(s):  
Or Ben-Zvi ◽  
Daniel Wangpraseurt ◽  
Omri Bronstein ◽  
Gal Eyal ◽  
Yossi Loya
Keyword(s):  
Optical Properties ◽  
Fluorescent Proteins ◽  
Light Attenuation ◽  
Coral Tissue ◽  
Coral Host ◽  
Natural Habitats ◽  
Algal Symbionts ◽  
Light Quantity ◽  
Photosynthetic Performances ◽  
The Relationship

Mesophotic coral ecosystems (MCEs) are light-dependent coral-associated communities found at 30–150 m depth. Corals inhabiting these deeper reefs are often acclimatized to a limited and blue-shifted light environment, enabling them to maintain the relationship with their photosynthetic algal symbionts (family Symbiodiniaceae) despite the seemingly suboptimal light conditions. Among others, fluorescent proteins produced by the coral host may play a role in the modulation of the quality and spectral distribution of irradiance within the coral tissue through wavelength transformation. Here we examined the bio-optical properties and photosynthetic performances of different fluorescence morphs of two mesophotic coral species Goniopora minor and Alveopora ocellata, in order to test the photosynthesis enhancement hypothesis proposed for coral fluorescence. The green morph of G. minor and the low fluorescence morph of A. ocellata exhibit, in their natural habitats, higher abundance. The morphs also presented different spectral reflectance and light attenuation within the tissue. Nevertheless, chlorophyll a fluorescence-based, and O2 evolution measurements, revealed only minor differences between the photosynthetic abilities of three fluorescence morphs of the coral G. minor and two fluorescence morphs of A. ocellata. The fluorescence morphs did not differ in their algal densities or chlorophyll concentrations and all corals harbored Symbiodiniaceae from the genus Cladocopium. Thus, despite the change in the internal light quantity and quality that corals and their symbionts experience, we found no evidence for the facilitation or enhancement of photosynthesis by wavelength transformation.

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.

Optical properties, of waters in the Murray-Darling Basin, South-eastern Australia

1990 ◽  
Vol 41 (5) ◽  
pp. 581 ◽  
Author(s):  
RL Oliver
Keyword(s):  
Optical Properties ◽  
Relative Role ◽  
Yellow Colour ◽  
Scattering Coefficients ◽  
Inherent Optical Properties ◽  
Murray Darling Basin ◽  
Eastern Australia ◽  
The Relationship

Apparent and inherent optical properties were determined for a range of water types in the Murray- Darling basin by using a combination of field and laboratory techniques. The absorption coefficient was calculated directly from in situ irradiance measurements of photosynthetically active radiation, whereas the scattering coefficient was determined from the irradiance measurements in conjunction with published nomograms relating the apparent and inherent optical properties. The validity of the nomograms for use in these waters was confirmed by comparing values of the average cosine calculated directly from in situ measurements with those estimated from the nomograms. These were closely correlated except for sites with chlorophyll concentrations greater than 200 mg m-3. The scattering coefficients estimated from the nomograms were approximately numerically equal to the turbidity in nephelometric turbidity units, but the variability of the relationship made it unsuitable for checking the validity of the nomograms. The relative role of dissolved and particulate components in the absorption and scattering of irradiance was examined by using spectrophotometry and linear regression of inherent optical properties on concentrations of the components. Estimates of specific absorption and scattering coefficients for algae, non-chlorophyllous suspended particles, and dissolved yellow colour were comparable to similar coefficients reported in the literature. The relative importance of these components to absorption and scattering varied considerably between sites and demonstrated the need for information on inherent optical properties in understanding the factors causing changes in optical water quality.

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