Algorithms for determining the absorption coefficient for aquatic particulates using the quantitative filter technique

Mitchell, B. G.

doi:10.1117/12.21440

Cited by 364 publications

(304 citation statements)

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“…Samples were kept in liquid nitrogen for 1 week and stored at -80°C prior to analysis. We measured the optical density of the particles (OD p ðkÞ) from 400 to 800 nm (1 nm resolution) using a slight variation of the quantitative filter technique (QFT) (Mitchell 1990). Notably, our method differed from the QFT in two respects: we used GF/C-filters (1.2 lm pore size) instead of GF/F (0.7 lm), and sandwiched the water-saturated sample filter between two glass slides instead of mounting it on a glass slide.…”

Section: Absorption Measurementsmentioning

confidence: 99%

The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity

2014

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Colored dissolved organic matter (CDOM) absorbs a substantial fraction of photosynthetically active radiation (PAR) in boreal lakes. However, few studies have systematically estimated how this light absorption influences pelagic primary productivity. In this study, 75 boreal lakes spanning wide and orthogonal gradients in dissolved organic carbon (DOC) and total phosphorus (TP) were sampled during a synoptic survey. We measured absorption spectra of phytoplankton pigments, CDOM, and non-algal particles to quantify the vertical fate of photons in the PAR region. Area-specific rates of gross primary productivity (PP A ) were estimated using a bio-optical approach based on phytoplankton in vivo light absorption and the light-dependent quantum yield of photochemistry in PSII measured by a PAM fluorometer. Subsequently, we calculated the effects of CDOM, DOC, and TP concentration on PP A . CDOM absorbed the largest fraction of PAR in the majority of lakes (mean 56.3%, range 36.9-76.2%), phytoplankton pigments captured a comparatively minor fraction (mean 6.6%, range 2.2-28.2%). PP A estimates spanned from 45 to 993 mg C m -2 day -1 (median 286 mg C m -2 day -1 ). We found contrasting effects of CDOM (negative) and TP (positive) on PP A . The use of DOC or CDOM as predictors gave very similar results and the negative effect of these variables on PP A can probably be attributed to shading. A future scenario of increased DOC, which is highly correlated with CDOM in these lakes, might impose negative effects on areal primary productivity in boreal lakes.

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Section: Absorption Measurementsmentioning

confidence: 99%

The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity

2014

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“…Each scan was corrected for scattering errors by offsetting the spectra with the mean absorption between 740 and 750 nm. A path length amplification correction was determined for monospecific cultures according to Mitchell (1990). These data were used to compare the magnitudes and spectral shapes of absorption coefficients obtained from the QFT and TR methods.…”

Section: Particulate Absorption Coefficientsmentioning

confidence: 99%

Variability in the light absorption coefficients of phytoplankton, non-algal particles, and colored dissolved organic matter in a subtropical bay (Brazil)

Ferreira

Ciotti

Giannini

2014

Estuarine, Coastal and Shelf Science

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“…Seawater samples collected off Heron Reef {3.45 S, 51.95 E} in the southern GBR were filtered, frozen, stored, and analyzed following the Ocean Optics Protocols [Mitchell et al, 2002]. Photometric measurements were conducted using a Perkin-Elmer Lambda 35 Spectrophotometer with an integrating sphere attachment following the quantitative filter technique [Mitchell, 1990;Mitchell et al, 2002]. Values of a / k ð Þ were normalized to 1.0 at 443 nm and are presented below in Table B1.…”

Section: Appendix Bmentioning

confidence: 99%

A semianalytical ocean color inversion algorithm with explicit water column depth and substrate reflectance parameterization

et al. 2015

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A semianalytical ocean color inversion algorithm was developed for improving retrievals of inherent optical properties (IOPs) in optically shallow waters. In clear, geometrically shallow waters, light reflected off the seafloor can contribute to the water-leaving radiance signal. This can have a confounding effect on ocean color algorithms developed for optically deep waters, leading to an overestimation of IOPs. The algorithm described here, the Shallow Water Inversion Model (SWIM), uses pre-existing knowledge of bathymetry and benthic substrate brightness to account for optically shallow effects. SWIM was incorporated into the NASA Ocean Biology Processing Group's L2GEN code and tested in waters of the Great Barrier Reef, Australia, using the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua time series (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013). SWIM-derived values of the total non-water absorption coefficient at 443 nm, a t (443), the particulate backscattering coefficient at 443 nm, b bp (443), and the diffuse attenuation coefficient at 488 nm, K d (488), were compared with values derived using the Generalized Inherent Optical Properties algorithm (GIOP) and the Quasi-Analytical Algorithm (QAA). The results indicated that in clear, optically shallow waters SWIM-derived values of a t (443), b bp (443), and K d (443) were realistically lower than values derived using GIOP and QAA, in agreement with radiative transfer modeling. This signified that the benthic reflectance correction was performing as expected. However, in more optically complex waters, SWIM had difficulty converging to a solution, a likely consequence of internal IOP parameterizations. Whilst a comprehensive study of the SWIM algorithm's behavior was conducted, further work is needed to validate the algorithm using in situ data.

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Algorithms for determining the absorption coefficient for aquatic particulates using the quantitative filter technique

Cited by 364 publications

References 0 publications

The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity

The Absorption of Light in Lakes: Negative Impact of Dissolved Organic Carbon on Primary Productivity

Variability in the light absorption coefficients of phytoplankton, non-algal particles, and colored dissolved organic matter in a subtropical bay (Brazil)

A semianalytical ocean color inversion algorithm with explicit water column depth and substrate reflectance parameterization

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