Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers

Galeron, Marie-Aimée; Amiraux, Rémi; Charrìère, Bruno; Radakovitch, Olivier; Raimbault, Patrick; Garcia, Nicole; Lagadec, Véronique; Vaultier, Frédéric; Rontani, J.‐F.

doi:10.5194/bg-12-1431-2015

Cited by 20 publications

(21 citation statements)

References 74 publications

(92 reference statements)

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“…Previous results obtained in the Rhône [5] and Mackenzie [6] Rivers clearly showed that the SPM of terrestrial origin found in major coastal rivers has been intensely autoxidized even before reaching the ocean, but the results obtained in this study confirm that metal ions present in the water have favored this autoxidation, and will favor it in seawater. In coastal environments, it is possible that the metal ions necessary to induce this autoxidation could be desorbed from SPM upon its arrival at sea [15,16].…”

Section: Rhone River Spm Incubationssupporting

confidence: 52%

“…Because sitosterol alone cannot be unambiguously attributed to organic matter of terrestrial origin (possible production by freshwater plankton [5]), we have compared its autoxidation rates to those of other compounds of a more clearly terrestrial origin. In all incubations, we determined autoxidative degradation rates for three families of lipid tracers: sitosterol, α-/β-amyrins, and betulin.…”

Section: Resultsmentioning

confidence: 99%

“…With the recent observations made in situ on both the Rhône and the Mackenzie Rivers, where it has been demonstrated that autoxidation is a major degradative process [5,6], we expected betulin, sitosterol and α-and β-amyrins to be fairly autoxidized, even at the start of our experiment. The observed state of degradation of the incubated SPM is in line with those results, clearly indicating that whether we are looking at particles or leaf debris, autoxidation has been involved in their degradation, whether on land or during riverine transport.…”

Section: Rhone River Spm Incubationsmentioning

confidence: 89%

“…In light of recent observations made in the Rhône River [5] and during in vitro experiments [9,10], we selected a set of lipid tracers allowing us to trace both the origin of SPM and the degradative processes undergone by lipids in SPM.…”

Section: Tracers Usedmentioning

confidence: 99%

“…It has been previously demonstrated that autoxidation is a major degradative process in rivers [5] and that it is enhanced upon the POM's arrival at sea [6].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Metal Ions and Hydroperoxide Content: Main Drivers of Coastal Lipid Autoxidation in Riverine Suspended Particulate Matter and Higher Plant Debris

Galeron

Radakovitch

Charrìère

et al. 2016

JMSE

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Autoxidation is a complex abiotic degradation process, and while it has long been known and well studied in biological compounds, it has been widely overlooked in environmental samples and as a part of environmental processes. With recent observations showing the magnitude of the involvement of autoxidation in coastal environments, it has become critical to better understand how and why this degradative process takes place. At the riverine/marine interface, recent findings evidenced a spike in autoxidation rates upon the arrival of suspended particulate matter in seawater. In this study, we aimed at identifying autoxidation-favoring factors in vitro by analyzing suspended particulate matter incubated under different conditions. If metal ions have long been known to induce autoxidation in biological systems, we show that they indeed induce autoxidation in particulate matter incubated in water, but also that the content in photochemically-produced hydroperoxides in suspended particulate matter is crucial to the induction of its autoxidation in water.

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Section: Rhone River Spm Incubationssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Rhone River Spm Incubationsmentioning

confidence: 89%

Section: Tracers Usedmentioning

confidence: 99%

“…It has been previously demonstrated that autoxidation is a major degradative process in rivers [5] and that it is enhanced upon the POM's arrival at sea [6].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Metal Ions and Hydroperoxide Content: Main Drivers of Coastal Lipid Autoxidation in Riverine Suspended Particulate Matter and Higher Plant Debris

Galeron

Radakovitch

Charrìère

et al. 2016

JMSE

View full text Add to dashboard Cite

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Autoxidation as a major player in the fate of terrestrial particulate organic matter in seawater

et al. 2017

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The Rhône River plays a major role in the Mediterranean Sea, being both its main freshwater source and its major particulate matter provider. This survey of the fate of terrestrial particulate organic matter (POM) was conducted along the salinity gradient of the Rhône River plume, between 2012 and 2014. It revealed that autoxidation acts rapidly and intensely upon the POM's arrival at sea, with α‐amyrin and β‐amyrin autoxidation rates going from 12.9 ± 2.9% to 45.0 ± 6.4% and 10.7 ± 4.0% to 50.3 ± 4.4%, respectively, between fresh water (salinity 0) and seawater (salinity 38). These compounds, being unambiguous markers of the terrestrial origin of POM, allow us to unequivocally characterize the POM as terrestrial. While it was originally believed that a desorption of redox‐active trace metal ions was the favoring factor that kick‐started this intense autoxidation, this study evidences no trace metal desorption in the Rhône River mixing zone and hence no correlation between high autoxidation rates and the presence of trace metal ions. Autoxidation rates however were very well correlated with salinity levels within the river plume, with r2 reaching 0.801, 0.962, and 0.943 for sitosterol, α‐amyrin, and β‐amyrin, respectively, in November 2014.

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Microbially driven fate of terrigenous particulate organic matter in oceans

Zhang

Chen

Zheng

et al. 2022

Limnology & Oceanography

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A long-standing enigma in oceanography is why terrestrial organic matter is "missing" in the global ocean, despite the considerable discharge into it every year. Although some explanations, such as mineralogical composition, hydrodynamic processes, and priming effect, have been proposed, we hypothesize that the essential mechanism behind the missing organic matter is microbial processing, for which the underlying coupled geochemical, molecular, and genetic evidence is unknown. An ultra-large-volume, long-term river-seawater stratified simulation system was constructed to unravel the microbially driven fate of terrigenous particulate organic matter (POM) in oceans. Analysis of combining the molecular with POM chemical composition data suggests that Bacteroidetes could act as pioneers in the processing of terrigenous POM in oceans, degrading high-molecular-weight, high-carbon compounds such as polysaccharides. Remaining low-molecular-weight nitrogenous organic matter is subsequently degraded by Planctomycetes and Proteobacteria. Isotopic signals show that this preferential degradation causes a distinct "aging" effect of POM, and along with nitrification enhanced by remineralization, causes a decrease in the POM C : N ratio. Degradation of terrigenous POM and bacterial biomass biosynthesis leads to positive deviations in δ 15 N and δ 13 C. Relatively refractory hydrocarbons, aromatic compounds, and phenols are accumulated by microbial processes in this system. This study provides mechanistic insights into the missing chemical and isotopic signals and microbially driven fate of terrigenous POM in the ocean, with important implications for how riverine material input affects marine carbon and nitrogen cycling.Ongoing climate change is expected to lead to increased global river runoff (Labat et al. 2004;Andersson et al. 2015). Both ecological modeling and field research have indicated that the flux of terrestrial input to oceans increases with increased river runoff (Andersson et al. 2015). However, few molecular signals of abundant terrestrial organic matter are detected in marine environments (Hedges et al. 1997;Bianchi 2011;Kandasamy and Nath 2016), and only a trace of terrigenous organic matter (e.g., lignin) is present in the ocean (Opsahl and Benner 1997). A proposed explanation for this is a priming effect, in which the addition of labile organic carbon increases remineralization of the relatively refractory organic carbon (Bianchi 2011;Morling et al. 2017). Mineralogical composition and characteristics have also been proposed as important factors controlling the fate of continentally

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Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers

Cited by 20 publications

References 74 publications

Metal Ions and Hydroperoxide Content: Main Drivers of Coastal Lipid Autoxidation in Riverine Suspended Particulate Matter and Higher Plant Debris

Metal Ions and Hydroperoxide Content: Main Drivers of Coastal Lipid Autoxidation in Riverine Suspended Particulate Matter and Higher Plant Debris

Autoxidation as a major player in the fate of terrestrial particulate organic matter in seawater

Microbially driven fate of terrigenous particulate organic matter in oceans

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