D. Stramski (stramski@mpl.ucsd.edu) is with the Marine Physical Laboratory, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0238. USA
A. Bricaud and A. Morel are with the Laboratoire de Physique et Chimie Marines, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, B.P. 8, 06238 Villefranche-sur-Mer, France.
Dariusz Stramski, Annick Bricaud, and André Morel, "Modeling the inherent optical properties of the ocean based on the detailed composition of the planktonic community," Appl. Opt. 40, 2929-2945 (2001)
We describe an approach to modeling the ocean’s inherent optical
properties (IOPs) that permits extensive analyses of IOPs as the
detailed composition of suspended particulate matter is varied in a
controlled manner. Example simulations of the IOP model, which
includes 18 planktonic components covering a size range from
submicrometer viruses and heterotrophic bacteria to microplanktonic
species of 30-µm cell diameter, are discussed. Input data
to the model include the spectral optical cross sections on a per
particle basis and the particle-number concentration for each
individual component. This approach represents a significant
departure from traditional IOP and bio-optical models in which the
composition of seawater is described in terms of a few components only
or chlorophyll concentration alone. The simulations illustrate how
the separation and understanding of the effects of various types of
particle present within a water body can be achieved. In an example
simulation representing an oligotrophic water body with a chlorophyll
a concentration of 0.18 mg m-3, the planktonic
microorganisms altogether are the dominant particulate component in the
process of light absorption, but their relative contribution to light
scattering is smaller than that of nonliving particles. A series of
simulations of water bodies with the same chlorophyll a
concentration but dominated by different phytoplankton species shows
that composition of the planktonic community is an important source of
optical variability in the ocean.
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Values for the average equivalent
spherical diameter D, the real part of the refractive index
at 550 nm n, imaginary part of the refractive index at 440
and 675 nm n′, and chlorophyll a content per cell
Chlcell are shown for each component. A taxonomic
class of planktonic species is in parentheses. References that
provide data are also indicated.
Table 2
Spectral Absorption σa,
Scattering σb, and Backscattering
σbb Cross Sections for the Generic Components
of Detrital Particles, Mineral Particles, and Air
Bubblesa
Component
Absorption
Scattering
Backscattering
Detritus
σa,det(λ) = 8.791 × 10-4 × exp(-0.00847λ)
σb,det(λ) = 0.1425λ-0.9445
σbb,det(λ) = 5.881 × 10-4 λ-0.8997
Minerals
σa,min(λ) = 1.013 × 10-3 × exp(-0.00846λ)
σb,min(λ) = 0.7712λ-0.9764
σbb,min(λ) = 1.790 × 10-2 λ-0.9140
Bubbles
σa,bub(λ) = 0
σb,bub(λ) = 4607.873 (±5.555)
σbb,bub(λ) = 55.359 (±0.373)
Best-fit equations for detrital and
mineral components are shown. The squared correlation coefficients
for these relationships (as calculated after appropriate logarithmic
transformation of variables) are greater than 0.999. The
scattering of the bubble component is nearly independent of λ, so the
average values and standard deviations (in parentheses) based on
all spectral values between 350 and 750 nm are given. The cross
sections are in units of µm2, and λ is in
nanometers. We caution against indiscriminate use of the magnitudes
of these cross sections (see text for details).
Table 3
Particle Number and Chlorophyll a
Concentrations of Various Particulate Components Used in the Base
Simulation of the IOP Modela
Component
Concentration (particles/m3)
Chl a (mg m-3)
VIRU
2.5 × 1012
0
HBAC
1.0 × 1011
0
PROC
1.75 × 1010
2.5654 × 10-2
SYNE
5.0 × 109
1.0076 × 10-2
SYMA
2.0 × 109
8.9940 × 10-3
PING
1.1264 × 108
1.3499 × 10-2
PSEU
2.4520 × 107
7.5798 × 10-3
LUTH
2.4809 × 107
2.6852 × 10-3
GALB
1.2097 × 107
3.8830 × 10-3
HUXL
1.0848 × 107
2.6001 × 10-3
CRUE
1.1240 × 107
3.2161 × 10-3
FRAG
1.1920 × 107
3.9260 × 10-3
PARV
1.5619 × 107
4.5122 × 10-3
BIOC
0.9915 × 107
2.2511 × 10-2
TERT
0.8925 × 107
1.5217 × 10-2
CURV
0.7467 × 107
2.4745 × 10-3
ELON
4.25 × 106
3.9883 × 10-2
MICA
5.0 × 105
1.2692 × 10-2
DET
8.25 × 1013
0
MIN
2.75 × 1013
0
BUB
1.775 × 106
0
Picoplankton
1.245 × 1011
4.4724 × 10-2
Small nanoplankton
2.5 × 108
8.2104 × 10-2
Total plankton
2.6248 × 1012
0.1794
Total nonliving particles
1.1 × 1014
0
Picoplankton is the sum of HBAC, PROC,
SYNE, and SYMA, Small nanoplankton is the sum of 11 phytoplankton
components from PING through CURV, and Total plankton includes all 18
planktonic components from VIRU through MICA. Total nonliving
particles represent the sum of DET and MIN, and BUB indicates the air
bubble component.
Table 4
Cell and Chlorophyll-a Concentrations of Bloom-Forming
Phytoplankton Species Used in the Model Simulations of
Bloomsa
Bloom-Forming Component
Concentration (cells/m3)
Chl a (mg m-3)
PROC (Prochlorophytes)
3.85 × 1011
0.5644
SYNE (Cyanobacteria)
2.725 × 1011
0.5491
PING (Small flagellates)
3.8636 × 109
0.5551
LUTH
8.5096 × 108
PSEU (Small diatoms)
1.7679 × 109
0.5465
BIOC (Medium-sized green algae)
1.5150 × 108
0.5765
TERT
1.3637 × 108
ELON (Relatively large flagellates)
6.1668 × 107
0.5787
MICA (Large dinoflagellates)
2.1725 × 107
0.5515
Note that five blooms are produced by a
single species. In the two remaining cases, two species of similar
cell size from the same taxonomic class are grouped together to produce
a bloom. The total chlorophyll a concentration in the
simulation of each bloom is ∼0.718 mg m-3.
Values for the average equivalent
spherical diameter D, the real part of the refractive index
at 550 nm n, imaginary part of the refractive index at 440
and 675 nm n′, and chlorophyll a content per cell
Chlcell are shown for each component. A taxonomic
class of planktonic species is in parentheses. References that
provide data are also indicated.
Table 2
Spectral Absorption σa,
Scattering σb, and Backscattering
σbb Cross Sections for the Generic Components
of Detrital Particles, Mineral Particles, and Air
Bubblesa
Component
Absorption
Scattering
Backscattering
Detritus
σa,det(λ) = 8.791 × 10-4 × exp(-0.00847λ)
σb,det(λ) = 0.1425λ-0.9445
σbb,det(λ) = 5.881 × 10-4 λ-0.8997
Minerals
σa,min(λ) = 1.013 × 10-3 × exp(-0.00846λ)
σb,min(λ) = 0.7712λ-0.9764
σbb,min(λ) = 1.790 × 10-2 λ-0.9140
Bubbles
σa,bub(λ) = 0
σb,bub(λ) = 4607.873 (±5.555)
σbb,bub(λ) = 55.359 (±0.373)
Best-fit equations for detrital and
mineral components are shown. The squared correlation coefficients
for these relationships (as calculated after appropriate logarithmic
transformation of variables) are greater than 0.999. The
scattering of the bubble component is nearly independent of λ, so the
average values and standard deviations (in parentheses) based on
all spectral values between 350 and 750 nm are given. The cross
sections are in units of µm2, and λ is in
nanometers. We caution against indiscriminate use of the magnitudes
of these cross sections (see text for details).
Table 3
Particle Number and Chlorophyll a
Concentrations of Various Particulate Components Used in the Base
Simulation of the IOP Modela
Component
Concentration (particles/m3)
Chl a (mg m-3)
VIRU
2.5 × 1012
0
HBAC
1.0 × 1011
0
PROC
1.75 × 1010
2.5654 × 10-2
SYNE
5.0 × 109
1.0076 × 10-2
SYMA
2.0 × 109
8.9940 × 10-3
PING
1.1264 × 108
1.3499 × 10-2
PSEU
2.4520 × 107
7.5798 × 10-3
LUTH
2.4809 × 107
2.6852 × 10-3
GALB
1.2097 × 107
3.8830 × 10-3
HUXL
1.0848 × 107
2.6001 × 10-3
CRUE
1.1240 × 107
3.2161 × 10-3
FRAG
1.1920 × 107
3.9260 × 10-3
PARV
1.5619 × 107
4.5122 × 10-3
BIOC
0.9915 × 107
2.2511 × 10-2
TERT
0.8925 × 107
1.5217 × 10-2
CURV
0.7467 × 107
2.4745 × 10-3
ELON
4.25 × 106
3.9883 × 10-2
MICA
5.0 × 105
1.2692 × 10-2
DET
8.25 × 1013
0
MIN
2.75 × 1013
0
BUB
1.775 × 106
0
Picoplankton
1.245 × 1011
4.4724 × 10-2
Small nanoplankton
2.5 × 108
8.2104 × 10-2
Total plankton
2.6248 × 1012
0.1794
Total nonliving particles
1.1 × 1014
0
Picoplankton is the sum of HBAC, PROC,
SYNE, and SYMA, Small nanoplankton is the sum of 11 phytoplankton
components from PING through CURV, and Total plankton includes all 18
planktonic components from VIRU through MICA. Total nonliving
particles represent the sum of DET and MIN, and BUB indicates the air
bubble component.
Table 4
Cell and Chlorophyll-a Concentrations of Bloom-Forming
Phytoplankton Species Used in the Model Simulations of
Bloomsa
Bloom-Forming Component
Concentration (cells/m3)
Chl a (mg m-3)
PROC (Prochlorophytes)
3.85 × 1011
0.5644
SYNE (Cyanobacteria)
2.725 × 1011
0.5491
PING (Small flagellates)
3.8636 × 109
0.5551
LUTH
8.5096 × 108
PSEU (Small diatoms)
1.7679 × 109
0.5465
BIOC (Medium-sized green algae)
1.5150 × 108
0.5765
TERT
1.3637 × 108
ELON (Relatively large flagellates)
6.1668 × 107
0.5787
MICA (Large dinoflagellates)
2.1725 × 107
0.5515
Note that five blooms are produced by a
single species. In the two remaining cases, two species of similar
cell size from the same taxonomic class are grouped together to produce
a bloom. The total chlorophyll a concentration in the
simulation of each bloom is ∼0.718 mg m-3.