Enhanced red fluorescence emission in the oxygen minimum zone of the Arabian Sea

Breves, Wiebke; Heuermann, R.; Reuter, R.

doi:10.1007/s10236-003-0026-y

Cited by 11 publications

(17 citation statements)

References 27 publications

(35 reference statements)

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“…415 nm that is similar to the shoulder found in the Arabian Sea in 600 m (Breves and Reuter, 2000;Breves, 2001;Breves et al, 2003). The shoulder was absent in samples from the sea surface, most pronounced at depths below the surface mixing layer, i.e.…”

Section: Cdom and Particulate Absorption Of Subsurface Waterssupporting

confidence: 49%

“…7). The fluorescence analysis of these extracts was initiated by the observation of a specific fluorescence at 660 nm (Ex: 420 nm) in the OMZ of the Arabian Sea (Breves, 2000;Breves et al, 2003). The authors speculated that this fluorescence was related to a 415-nm CDOM absorption shoulder observed in the same depths.…”

Section: Cdom Extractsmentioning

confidence: 99%

“…415 nm, the CDOM and particulate absorption spectra of water samples were analyzed with a least-square fit as done by Breves et al (2003). The absorption was fitted in the range of 370-600 nm to:…”

Section: Light Absorption Measurementsmentioning

confidence: 99%

“…A previous CDOM absorption study in mesopelagic waters (600 m) of the Arabian Sea showed an absorption shoulder in the visible wavelengths at around 415 nm (Breves and Reuter, 2000;Breves, 2001;Breves et al, 2003). The observation of the shoulder was hypothesized to be related to a chlorophyll a-like fluorescence observed in the same water depth (Breves, 2001;Breves et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…It is, however, still unresolved whether the red fluorescence occurs in the particulate and/or dissolved fraction. Breves et al (2003) concluded that it is most likely in the dissolved phase based on sample filtration and a fluorescence emission at ∼ 650 nm, which appeared in samples from mesopelagic depth when excited with light of 420 nm. This contradicts earlier results (Broenkow et al, 1992) which often found a close correlation of the "deep red fluorescence" with light attenuation (mainly scattering by particles).…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic detection of a ubiquitous dissolved pigment degradation product in subsurface waters of the global ocean

Röttgers

Koch

2012

Biogeosciences

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Abstract. Measurements of light absorption by chromophoric dissolved organic matter (CDOM) from subsurface waters of the tropical Atlantic and Pacific Oceans showed a distinct absorption shoulder at 410-415 nm. This indicates an underlying absorption of a pigment whose occurrence is partly correlated with the apparent oxygen utilization (AOU) but also found in the deep chlorophyll maximum. A similar absorption maximum at ∼ 415 nm was also found in the particulate fraction of samples taken below the surface mixing layer and is usually attributed to absorption by respiratory pigments of heterotrophic unicellular organisms. In our study, fluorescence measurements of pre-concentrated dissolved organic matter (DOM) samples from 200-6000 m confirmed a previous study suggesting that the absorption at ∼ 415 nm was related to fluorescence at 650 nm in the oxygen minimum zone. The absorption characteristics of this fluorophore was examined by fluorescence emission/excitation analysis and showed a clear excitation maximum at 415 nm that could be linked to the absorption shoulder in the CDOM spectra. The spectral characteristics of the substance found in the dissolved and particulate fraction did not match with those of chlorophyll a degradation products (as found in a sample from the sea surface) but can be explained by the occurrence of porphyrin pigments from either heterotrophs or autotrophs. Combining the observations of the fluorescence and the 415-nm absorption shoulder suggests that there are high concentrations of a pigment degradation product in subsurface DOM of all major oceans. Most pronouncedly we found this signal in the deep chlorophyll maximum and the oxygen minimum zone of tropical regions. The origin, chemical nature, turnover rate, and fate of this molecule is so far unknown.

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Section: Cdom and Particulate Absorption Of Subsurface Waterssupporting

confidence: 49%

Section: Cdom Extractsmentioning

confidence: 99%

Section: Light Absorption Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spectroscopic detection of a ubiquitous dissolved pigment degradation product in subsurface waters of the global ocean

Röttgers

Koch

2012

Biogeosciences

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Chromophoric signatures of microbial by‐products in the dark ocean

Catalá

Reche

Ramón

et al. 2016

Geophysical Research Letters

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Detailed examination of the absorption spectra from dark ocean samples allowed us to identify and deconvolve two distinct chromophores centered at 302 nm (UV) and 415 nm (visible) from the exponential decay curve characteristic of humic substances. The UV chromophore was ubiquitous in intermediate and deep waters, and it has been proposed as the secondary absorption peak of nitrate. The visible chromophore was prominent at the central and intermediate water masses of the North Pacific, and it has been proposed as cytochrome c. Subtraction of the modeled absorption spectra of the two chromophores from the measured absorption spectrum of the samples leads to a spectral slope overestimation by 13.3 ± 6.0% for S275–295 and 14.8 ± 10.6% for S350–400. To only consider the chromophoric fraction of DOM, the absorption spectra of nitrate should be subtracted in samples with a [NO3−]:a302 ratio > 70 µM m.

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Correction of profiles of in‐situ chlorophyll fluorometry for the contribution of fluorescence originating from non‐algal matter

Xing

Claustre

Boss

et al. 2016

Limnology & Ocean Methods

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In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll‐a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio‐Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal “deep sea red fluorescence” features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio‐Argo floats), we show that the fluorescence signal measured by a humic‐like DOM fluorometer is highly correlated to the “deep sea red fluorescence.” Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non‐algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so‐called “deep‐offset correction”), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio‐Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality‐control and correction of chlorophyll a fluorescence originating from Bio‐Argo network.

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Enhanced red fluorescence emission in the oxygen minimum zone of the Arabian Sea

Cited by 11 publications

References 27 publications

Spectroscopic detection of a ubiquitous dissolved pigment degradation product in subsurface waters of the global ocean

Spectroscopic detection of a ubiquitous dissolved pigment degradation product in subsurface waters of the global ocean

Chromophoric signatures of microbial by‐products in the dark ocean

Correction of profiles of in‐situ chlorophyll fluorometry for the contribution of fluorescence originating from non‐algal matter

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