Fatty acid and stable isotope (δ13C, δ15N) signatures of particulate organic matter in the lower Amazon River: Seasonal contrasts and connectivity between floodplain lakes and the mainstem

Mortillaro, Jean-Michel; Abril, Gwénaël; Moreira-Turcq, Patrícia; Sobrinho, Rodrigo de Lima; Pérez, M.; Méziane, Tarik

doi:10.1016/j.orggeochem.2011.08.011

Cited by 69 publications

(84 citation statements)

References 70 publications

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“…9a, reflecting dominant input of in situ production, consistent with prior observations of Tapajós River POC composition (Mortillaro et al, 2011;Kim et al, 2012;Ward et al, 2015). The combination of a relatively deep euphotic zone depth and slower water velocities in the Tapajós River, especially during high water in July, encourages the growth of phytoplankton and cyanobacteria (Mortillaro et al, 2011). The highly depleted and anomalously low ACL fatty acids at the tributary surface (Figs.…”

Section: Prominent Soil-derived Poc Source To the Main Stemsupporting

confidence: 86%

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Rosengard¹

2017

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Particulate organic carbon (POC) in the ocean and mobilized by rivers on land transfers ~0.1% of global primary productivity to the deep ocean sediments. This small fraction regulates the long-term carbon cycle by removing carbon dioxide from the atmosphere for centuries to millennia. This thesis investigates mechanisms of POC transfer to the deep ocean by analyzing particles collected in transit through two globally significant carbon reservoirs: the Southern Ocean and the Amazon River Basin. These endeavors test the hypothesis that organic matter composition controls the recycling and transfer efficiency of POC to the deep ocean, and illustrate new applications for ramped pyrolysis/oxidation (RPO), a growing method of POC characterization by thermal stability. By coupling RPO to stable and radiocarbon isotope analyses of riverine POC, I quantify three thermally distinct soil organic carbon pools mobilized by the Amazon River, and evaluate the degradability and fate of these different pools during transport to the coastal Atlantic Ocean. More directly, RPO analyses of marine samples suggest that POC transfer in the water column is in fact selective. Observations of consistent biomolecular changes that accompany transport of phytoplankton-derived organic matter to depth across the Southern Ocean support the argument for preferential degradation of specific POC pools in the water column. Combining discussions of POC recycling and transfer across both marine and terrestrial systems offer new perspectives of thermal stability as a proxy for diagenetic stability and POC degradation state. The challenges of interpreting RPO data in these two environments set the stage for applying the technique to more controlled experiments that trace POC from source to long-term sink.

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Section: Prominent Soil-derived Poc Source To the Main Stemsupporting

confidence: 86%

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Rosengard¹

2017

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“…400 to 500 mg of sediment were weighted and used for the analysis. Fatty acid (FA) analysis was performed following the modified method of Bligh & Dyer (1959) as described in Mortillaro et al (2011 9…”

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confidence: 99%

Seasonal variations of the composition of microbial biofilms in sandy tidal flats: Focus of fatty acids, pigments and exopolymers

Passarelli

Méziane

Thiney

et al. 2015

Estuarine, Coastal and Shelf Science

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Biofilms, or microbial mats, are common associations of microorganisms in tidal flats; they generally consist of a large diversity of organisms embedded in a matrix of Extracellular Polymeric Substances (EPS). These molecules are mainly composed of carbohydrates and proteins, but their detailed monomer compositions and seasonal variations are currently unknown. Yet this composition determines the numerous roles of biofilms in these systems.This study investigated the changes in composition of carbohydrates in intertidal microbial mats over a year to decipher seasonal variations in biofilms and in varying hydrodynamic conditions. This work also aimed to assess how these compositions are related to microbial assemblages. In this context, natural biofilms whose development was influenced or not by artificial structures mimicking polychaete tubes were sampled monthly for over a year in intertidal flats of the Chausey archipelago. Biofilms were compared through the analysis of their fatty acid and pigment contents, and the monosaccharide composition of their EPS carbohydrates. Carbohydrates from both colloidal and bound EPS contained mainly glucose and, to a lower extent, galactose and mannose but they showed significant differences in their detailed monosaccharide compositions. These two fractions displayed different seasonal evolution, even if glucose accumulated in both fractions in summer; bound EPS only were affected by artificial biogenic structures. Sediment composition in fatty acids and pigments showed that microbial communities were dominated by diatoms and heterotrophic bacteria.Their relative proportions, as well as those of other groups like cryptophytes, changed between times and treatments. The changes in EPS composition were not fully explained by modifications of microbial assemblages but also depended on the processes taking place in sediments and on environmental conditions. These variations of EPS compositions are likely to alter different ecosystem processes such as biostabilisation or pollutants trapping.

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“…Although only 10-20 % of the organic matter (OM) produced in the water column reaches the sediment and is finally buried (Devol et al, 1984), the sediments in these lakes are important sinks of carbon (Moreira-Turcq et al, 2004). Most of the sedimentary organic matter (SOM) in freshwater systems is derived from terrestrial vascular plants (Goñi and Hedges, 1992;Moreira-Turcq et al, 2004;Mortillaro et al, 2011). In the Amazon basin, many studies have characterized the suspended particulate organic matter (SPOM) in the rivers and the floodplain lakes and concluded that the main sources of OM to the aquatic system are the forests and the upstream Andean soils (e.g., Hedges et al, 1986Hedges et al, , 1994Quay et al, 1992;Victoria et al, 1992;Moreira-Turcq et al, 2004Aufdenkampe et al, 2007;Mortillaro et al, 2011;Zell et al, 2013b).…”

Section: R L Sobrinho Et Al: Spatial and Seasonal Contrasts Of Sedmentioning

confidence: 99%

“…Most of the sedimentary organic matter (SOM) in freshwater systems is derived from terrestrial vascular plants (Goñi and Hedges, 1992;Moreira-Turcq et al, 2004;Mortillaro et al, 2011). In the Amazon basin, many studies have characterized the suspended particulate organic matter (SPOM) in the rivers and the floodplain lakes and concluded that the main sources of OM to the aquatic system are the forests and the upstream Andean soils (e.g., Hedges et al, 1986Hedges et al, , 1994Quay et al, 1992;Victoria et al, 1992;Moreira-Turcq et al, 2004Aufdenkampe et al, 2007;Mortillaro et al, 2011;Zell et al, 2013b). However, little is known about the molecular composition of the SOM in the floodplain lakes in general, and in particular, the contribution of the multiple sources of OM (upland soils, flooded and non-flooded forests, aquatic macrophytes, and phytoplankton) remains uncertain (Mortillaro et al, 2011;Zocatelli et al, 2011;Moreira et al, 2014).…”

Section: R L Sobrinho Et Al: Spatial and Seasonal Contrasts Of Sedmentioning

confidence: 99%

“…Most of the SOM is supposed to be transported to the floodplain lakes via Amazon River main stem during the rising and high water seasons Victoria et al, 1992;Moreira-Turcq et al, 2004Mortillaro et al, 2011). However, a significant increase in the vertical flux of OM was observed in Lake Curuai during the falling water season, which is interpreted as the result of resuspended sediments when the lake becomes smaller and shallower (MoreiraTurcq et al, 2004).…”

Section: R L Sobrinho Et Al: Spatial and Seasonal Contrasts Of Sedmentioning

confidence: 99%

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Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

et al. 2016

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Abstract. In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Mirituba and Curuai) which have different morphologies, hydrodynamics and vegetation coverages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ 13 C org ). These results were compared with lignin phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the crenarchaeol as an indicator of aquatic (rivers and lakes) OM. Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C 3 plant-derived OM. However, a downstream increase in C 4 macrophyte-derived OM contribution was observed along the gradient of increasing open waters -i.e., from upstream to downstream. Accordingly, we attribute the temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.

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Fatty acid and stable isotope (δ13C, δ15N) signatures of particulate organic matter in the lower Amazon River: Seasonal contrasts and connectivity between floodplain lakes and the mainstem

Cited by 69 publications

References 70 publications

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Novel analytical strategies for tracing the organic carbon cycle in marine and riverine particles

Seasonal variations of the composition of microbial biofilms in sandy tidal flats: Focus of fatty acids, pigments and exopolymers

Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

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