Photooxidation of triglycerides and fatty acids in seawater: Implication toward the formation of marine humic substances

Kieber, Robert J.; Hydro, Linda H.; Seaton, Pamela J.

doi:10.4319/lo.1997.42.6.1454

Cited by 189 publications

(149 citation statements)

References 24 publications

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“…Sources of CDOM include continental runoff that transports DOM, primarily from soils (Coble 2007); abiotic condensation and transformation of biopolymers (e.g., photo-oxidized polyunsaturated lipids released into the water column by plankton) (Kieber et al 1997); and in situ biological production (Yentsch and Reichert 1961;Kramer and Herndl 2004). Within these autochthonous sources, CDOM can be produced as a by-product of DOM metabolism, mainly by bacteria.…”

mentioning

confidence: 99%

Production of chromophoric dissolved organic matter by marine phytoplankton

Romera‐Castillo

Sarmento

Álvarez‐Salgado

et al. 2009

Limnology & Oceanography

263

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Incubation experiments with axenic cultures of four common phytoplankton species of the genera Chaetoceros, Skeletonema, Prorocentrum, and Micromonas were performed to test for the production of fluorescent dissolved organic matter (FDOM) by marine phytoplankton. Our results prove that the four species exuded both fluorescent protein-like and marine humic-like materials in variable amounts, with more production by the diatoms Chaetoceros sp. and Skeletonema costatum and less by Prorocentrum minimum. Whereas the exudation of protein-like substances by healthy phytoplankton cells has been recognized, the in situ production of marine humic-like substances is still a matter of debate. Using axenic cultures, we demonstrate unequivocally that phytoplankton can directly contribute to the autochthonous production of colored humic-like substances in the ocean. Extrapolation of these findings to the field indicates that about 20% of the marine humic-like substances produced in the highly productive coastal upwelling system of the Ría de Vigo could originate from growing phytoplankton. Therefore, the exudation of FDOM by marine phytoplankton should be considered in future studies of the dynamics of colored DOM in marine systems.

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mentioning

confidence: 99%

Production of chromophoric dissolved organic matter by marine phytoplankton

Romera‐Castillo

Sarmento

Álvarez‐Salgado

et al. 2009

Limnology & Oceanography

263

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“…Therefore, they were all implicitly assuming that marine humic substances should be a by-product of bacterial respiration processes (Brophy and Carlson 1989;Kramer and Herndl 2004). Other models, such as the condensation of poly-phenols (Hedges 1978) or the photooxidation of lipids (Kieber et al 1997) would restrict to estuaries, where poly-phenols of terrestrial origin can be abundant, and the surface ocean layer, where the UV radiation is able to oxidize triglycerides and fatty acids of planktonic origin.…”

Section: Discussionmentioning

confidence: 99%

“…Exposure to sunlight degrades high-molecular weight humic substances into smaller photoproducts that are mainly removed from the DOM pool by two pathways: through direct volatilization of carbon gases (CO, CO 2 , SO 2 , etc.) and through rapid bacterial utilization of labile photoproducts (Kieber et al 1997). The relationship between photochemical and heterotrophic processes has been investigated during the last decade in different environments (Lindell et al 1995;Moran et al 2000;Obernosterer and Benner 2004;Kramer and Herndl 2004).…”

mentioning

confidence: 99%

“…The origin of marine humic substances is not completely resolved. An alternative to the classical polyphenol and melanoidin condensation models (Hedges 1978) and the photo-oxidation of lipids (Kieber et al 1997) is the formation of humic substances as a byproduct of microbial respiration (Brophy and Carlson 1989;Kramer and Herndl 2004). A fraction of the respired organic carbon is transformed into biologically refractory organic matter instead of CO 2 (Chen and Bada 1992;Hayase and Shinozuka 1995).…”

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confidence: 99%

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Microbial and photochemical reactivity of fluorescent dissolved organic matter in a coastal upwelling system

2006

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We observed significant changes in the dissolved oxygen content and the fluorescence of humic substances and dissolved aromatic amino acids after 24 h light and dark incubations in the coastal upwelling system of the Ría de Vigo under a wide variety of meteorologic and oceanographic conditions. Respiration rates were inversely correlated with the net production of humic fluorescence in the dark at a net rate of 20.027 6 0.003 mg equivalents of quinine sulphate per mmol of O 2 , suggesting that marine humics are a by-product of the bacterial respiration of dissolved organic matter (DOM). On the contrary, humic fluorescence consumption in the light minus dark incubations was positively correlated with the net production in the dark, indicating a rapid photodegradation of recently produced marine humic substances. Parallel incubation experiments demonstrated that daily photodegradation rates and residual humic fluorescence levels followed a seasonal pattern characterized by a marked autumn maximum. Finally, a significant linear correlation between the gross primary production (Pg) and the net production of aromatic amino acids fluorescence in the light pointed to the rapid consumption of dissolved protein-like materials at a net average rate of 21.4 6 0.2 ppb equivalents of tryptophan per day, which accumulates in the water column only when Pg exceeds 80 6 20 mmol kg 21 d 21 .

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“…Although the production of DCAs from photooxidation of unsaturated fatty acids has been largely studied in the atmospheric aerosols, little is known about the direct and sensitized photoproduction of DCAs in aqueous solutions. In seawater, it has been shown that oleic acid, which is produced by phytoplankton [19], was directly photooxidized to produce ωC 9 and C 9ald [20]. However, there is no report of concentrations of a homologous series of DCAs from these photooxidation processes.…”

Section: Introductionmentioning

confidence: 97%

Hydroxyl radical-induced photochemical formation of dicarboxylic acids from unsaturated fatty acid (oleic acid) in aqueous solution

Tedetti

Kawamura

Narukawa

et al. 2007

Journal of Photochemistry and Photobiology A: Chemistry

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In this study, we assess under laboratory controlled conditions the direct and hydroxyl radical ( OH)-induced photochemical production of low molecular weight (LMW) dicarboxylic acids and related compounds (C 2 -C 9 ) (DCAs) from oleic acid (cis-9-octadecenoic, 9C 18 ) in aqueous solution. Nitrate (NO 3 -)-amended and unamended oleate solutions were irradiated under ultraviolet-B radiation (UV-B, 313 nm) for 5 h, with NO 3 -being the source of OH. The OH-induced photochemical production of DCAs (C 2di -C 9di ) (165 ± 32 nM h -1 ) was much higher than that induced by the direct effect of UV-B (33 ± 31 nM h -1 ), accounting for 85% of the total (direct + OH-induced) photochemical production of DCAs (C 2di -C 9di ) (194 ± 6 nM h -1 ). Azelaic acid (C 9di ) was the dominant photoproduct (comprising 63 and 44% of DCAs in the direct and OH-induced photochemical production, respectively) followed by C 8di , C 7di and C 6di , whereas shorter chain compounds (C 2di -C 5di ) were minor produced species. Using our estimate of OH photoproduction (P-OH in nM h -1 ), the production of C 9di from 50 µM of oleic acid was evaluated to ~ 36 nM (nM OH) -1 . We propose in this work a chemical mechanism for the reaction of OH with oleic acid in aqueous solution from the cleavage of its double bond, and the subsequent formation of DCAs through oxidation and decarboxylation processes.

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Photooxidation of triglycerides and fatty acids in seawater: Implication toward the formation of marine humic substances

Cited by 189 publications

References 24 publications

Production of chromophoric dissolved organic matter by marine phytoplankton

Production of chromophoric dissolved organic matter by marine phytoplankton

Microbial and photochemical reactivity of fluorescent dissolved organic matter in a coastal upwelling system

Hydroxyl radical-induced photochemical formation of dicarboxylic acids from unsaturated fatty acid (oleic acid) in aqueous solution

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