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| Titel |
Using a two-layered sphere model to investigate the impact of gas vacuoles on the inherent optical properties of Microcystis aeruginosa |
| VerfasserIn |
M. W. Matthews, S. Bernard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 12 ; Nr. 10, no. 12 (2013-12-11), S.8139-8157 |
| Datensatznummer |
250085471
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| Publikation (Nr.) |
 copernicus.org/bg-10-8139-2013.pdf |
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| Zusammenfassung |
| 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. |
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