Specific in vivo absorption coefficient of chlorophyll <i>a</i> at 675 nm1

Haardt, H.; Maske, Helmut

doi:10.4319/lo.1987.32.3.0608

Cited by 63 publications

(36 citation statements)

References 25 publications

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“…Values obtained at 675 nm were between 0.007 and 0.017 m2 (mg Chl a)-' (Table 2). This range of values is the result of the optical property of the individual cells of the sample and not related to methodological noise or systematic errors such as concentration dependence (Haardt and Maske 1987 ratios of absorption (cf. Table 2 and Fig.…”

Section: Resultsmentioning

confidence: 99%

“…"Suspension-collimated light" values were obtained by measuring phytoplankton suspensions in cuvcttes 200 mm long within an integrating sphere of 450-mm diameter. Details of this method are described elsewhere (Haardt and Maske 1987). Reproducibility was at the 0.0002-OD level.…”

Section: Methodsmentioning

confidence: 99%

“…Measuring seawater at natural concentrations of chlorophyll inside an integrating sphere calls for extremely high resolution and stability of radiative quantities because of high background absorption by water and dissolved matter. Means of achieving such resolution are discussed elsewhere (Haardt and Maske 1987). Shibata et al (1954) proposed a method in which opal glass is placed between the sample and the detector, thus changing the radiance detector of the photometer to a detector of irradiance (cosine characteris-I Research funded by the Bundesministerium Rir Forschung und Technologie MFG 00359, F.R.G.…”

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confidence: 99%

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Quantitative in vivo absorption spectra of phytoplankton: Detrital absorption and comparison with fluorescence excitation spectra1

Maske

Haardt

1987

Limnology & Oceanography

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Spectra1 absorption of phytoplankton from cultures and natural samples was measured on filters with various optical setups including collimated and diffuse irradiation and measurements ofwetted filters within an integrating sphere. In suspensions within an integrating sphere, specific absorption coefficients for laboratory cultures varied by a factor of only two.Measurements on filters yielded values dependent on filter load. Specific absorption coefficients derived from measurements of sample filters were considerably higher than values obtained from suspensions in an integrating sphere due to increased diffuseness of irradiance and to pathlength amplification by filter-particle and particle-particle interactions. Measured absorption of phytoplankton in the blue can be increased greatly by absorption of detritus, evident from absorption spectra of depigmented samples on filter. After subtracting detrital absorption, absorption spectra of phytoplankton are qualitatively similar to the corresponding quantum-corrected fluorescence excitation spectra. The detritus-corrected ratio of absorption at 440 vs. 675 nm shows average values between 1 and 1.5.Comparison with published values shows that specific in vivo absorption coefficients of phytoplankton arc mostly overestimated as a result of the methodology applied. In the blue region of the spectrum, overestimation of phytoplankton absorption in field samples is possible if detrital absorption is neglected.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Quantitative in vivo absorption spectra of phytoplankton: Detrital absorption and comparison with fluorescence excitation spectra1

Maske

Haardt

1987

Limnology & Oceanography

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“…If particle scattering varies inversely with X, however, the limits of overestimation are higher, 1.13-1.5 1 at 675 nm and 1.23-1.80 at 550 and 440 nm. Because the ground glass sidewalls scattered much less than the opal backwall, one guesses that actual overestimates were well below the upper limits and certainly below the twofold supposed by Haardt and Maske (1987). Evaluation of limits of error is all that can be done when data include only values of D, and D750.…”

Section: Methodsmentioning

confidence: 99%

“…They also supposed that X error would be small. Recently, Haardt and Maske (1987;also Maske and Haardt 1987) expressed a counterview, namely that scattering by an algal suspension and by opal glass would double the average path length of quanta. They thought that the optical density measured in opal glass might commonly be twice the absorption product of the suspended particles alone.…”

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Estimation of absorption coefficients of scattering suspensions using opal glass

Bannister

1988

Limnology & Oceanography

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Previously, the algal absorption product (absorption coefflcicnt at wavelength X times cuvette depth) was estimated as D, -D750, the difference in optical densities of a suspension, measured against water in opal glass cuvettes. Such estimates are subject to "cuvette error" dependent on dimensions and materials of the cuvettes and to "A error" due to inadequacy of 750 nm as a reference wavelength. Monte Carlo calculations were performed to assess cuvette error; then limits of the combined cuvette and X errors were explored. With cuvettes and suspensions used previously, the combined error was usually + 10% (lo-20% at 440 nm), not 100% as supposed in a recent publication. Cuvette error is minimal in cubical cuvettes with black sidewalls, but substantial X error may still occur. Both errors arc avoided in a method using two pairs of opal cuvettes. Weidemann and Bannister (1986) and Weidemann et al. (1985) concentrated algae or lake particulates and measured absorption spectra of the suspensions against water in rectangular cuvettes with opal glass backwalls. The difference, DA -D750, between optical densities at a wavelength X in the visible and at 750 nm (where algal absorption was presumed negligible) was taken as an estimate of the product of cuvette depth (d) and the volume absorption coefficient (a) of the algae or particles at X.Values of ad determined in this way may over-or underestimate true values of the algal absorption product. There are two sources of error. One, a "cuvette error," arises from the fact that the walls of opal glass cuvettes contribute to the diffusion of light in the suspension, as a result of which average path length becomes larger than cuvette depth. The magnitude of cuvette error depends on the dimensions and materials of the cuvettes. Herein, cuvette error is defined as the factor by which DA -D,,, overestimates the absorption product, ad, when the particles and suspending medium are ascribed "ideal properties." Ideal behavior assumes that the suspending medium does not scatter, absorption by the medium is either insignificant or else independent of X, particles do not absorb at 750 nm, and particle scattering is independent of X. A second error, here called "X error," arises when properties of a suspension depart from ideal ones, D75,, then becoming an inadequate correction. Scattering by water is too weak (b < 0.0 1 m-l : Kirk 1983) to contribute to X error. The absorption coefficient of water is X-dependent, however, and rises to -2.5 m-l at 750 nm; in 25-mm cuvettes, a small but significant X error would occur. There is some evidence that the algal scattering coefficient is inversely proportional to wavelength (Kirk 1983), and some studies have indicated significant particle absorption at 740 nm (Morel and Bricaud 198 1). I shall show that a large X error can arise from particle absorption at 750 nm or X-dependent particle scattering.Weidemann and Bannister (1986) supposed that their suspensions scattered light mainly through small angles and that diffuse light scatte...

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