Remineralization rates, recycling, and storage of carbon in Amazon shelf sediments

Aller, Robert C.; Blair, Neal E.; Xia, Qingyin; Rude, Peter D.

doi:10.1016/0278-4343(95)00046-1

Cited by 245 publications

(159 citation statements)

References 73 publications

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“…One probable explanation is that biogeochemical profiles sampled at water slack are not at steady state, as reported by Aller et al (1996) in Amazon shelf mud. Indeed, particle deposition might go faster than homogenization of dissolved species by turbulent diffusion.…”

Section: Stoichiometry Of Early Diagenesis and Carbonate Dissolution mentioning

confidence: 92%

“…thymidine incorporation and bacterial count data) rather than by macro-or meiofauna (Irigoien and Castel 1995); oxic and suboxic processes are dominant; and NH and Mn 2ϩ produced in the fluid mud are ϩ 4 repetitively reoxydized after resuspensions, respectively, by nitrification and precipitation. These characteristics make these systems act as efficient ''fluidized bed reactors'' (Aller 1998) for land-derived refractory POM decomposition.…”

Section: Stoichiometry Of Early Diagenesis and Carbonate Dissolution mentioning

confidence: 99%

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Oxic/anoxic oscillations and organic carbon mineralization in an estuarine maximum turbidity zone (The Gironde, France)

Abril

Etcheber

Hir³

et al. 1999

Limnology & Oceanography

152

121

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The study of vertical particle dynamics in the highly turbid Gironde Estuary has shown intense cycles of sedimentation and resuspension at both diurnal and neap-spring time scales. Fluid mud, with suspended particulate matter (SPM) concentrations between 50 and 500 g liter ) preferentially reworked at the neap-spring time scale. Due to the alternation of sedimentation and resuspension periods, most of the sediment experienced oxic/anoxic oscillations throughout the neap-spring cycle. Fluid mud resuspension occurred without any observable incidence on the surface-water oxygenation. An increase in total alkalinity was found in the fluid mud, due to both anaerobic respiration and a carbonate dissolution coupled to aerobic respiratory CO 2 generation. This phenomenon significantly affected the inorganic carbon budget of the estuary, increasing the HCO input to the coastal ocean and reducing the CO 2 flux to the atmosphere. An Ϫ 3 accumulation of labile-dissolved organic carbon observed in the fluid mud suggests that these oscillations result in an acceleration of particulate organic matter (POM) decomposition. In the Gironde MTZ, a net loss of refractory land-derived POM occurs. This system acts as an efficient oxic/suboxic ''fluidized bed reactor,'' similar to mobile deltaic muds.Understanding processes affecting carbon distribution through estuaries is of major importance for a better assessment of the contribution of world rivers to the carbon budget of the coastal ocean. The influence of tides in macrotidal estuaries increases the residence times of both water and 1 Present address: Université de Liège, Mécanique des Fluides Géophysiques, Unité d'Océanographie Chimique, Institut de Physique (B5), B-4000 Sart Tilman, Belgium. AcknowledgmentsThis work has been funded by the European Commission in the framework of the Biogest project (ENV4-CT96-0213); this is a contribution of the Eloise Projects network. It was also supported by the URM 13 project, linking IFREMER and the University of Bordeaux I.-DGO-UMR 5805. Fieldwork was carried out onboard the RV Gwen Drez (IFREMER, France), the RVs Côte d'Aquitaine and Côte de la Manche (INSU, France), and the RV Belgica (Belgium); we thank captains and crews. A. De Resseguier (DGO) built the fluid mud sampler and was present on the field for sampling assistance. We are grateful to P. Castaing and A. Sottolichio (DGO) for help in using the OBS and to A. V. Borges (University of Liège)

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Section: Stoichiometry Of Early Diagenesis and Carbonate Dissolution mentioning

confidence: 92%

Section: Stoichiometry Of Early Diagenesis and Carbonate Dissolution mentioning

confidence: 99%

Oxic/anoxic oscillations and organic carbon mineralization in an estuarine maximum turbidity zone (The Gironde, France)

Abril

Etcheber

Hir³

et al. 1999

Limnology & Oceanography

152

121

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“…Net rates of iron and manganese reduction were estimated in November 1997 with a core-incubation method (Aller et al 1996). Two sets of duplicate 20 cm long cores were subdivided into 4 cm long sections under a N2 atmosphere.…”

Section: Enterprise Tam Giangmentioning

confidence: 99%

Benthic decomposition rates and pathways in plantations of the mangrove Rhizophora apiculata in the Mekong delta, Vietnam

Alongi¹,

Tirendi²,

Trott³

et al. 2000

Mar. Ecol. Prog. Ser.

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Rates and pathways of organic matter decomposition were estimated in sediments of 6, 8 and 35 yr old Rhizophora apiculata plantations in the lower Mekong delta, Vietnam. Rates of total carbon oxidation ( T o , = average of CO, gas fluxes from exposed sediments + ZCO, fluxes from submerged sediments) were slowest in the 8 yr old forest (mean T o , = 17.1 mm01 C m-' d-'), with higher rates in the 6 yr old (mean To, = 48.1 mm01 C m-' d.') and 35 yr old forests (mean Tcox = 53.7 mm01 C m-2 d-'). In all 3 forests, sediments to a depth of 40 cm were acidic, with mostly positive redox potential: free sulfides and methane were not measurable in the pore water or across the sedirnenwwater-air interface. Oxic respiration was the malor decomposition pathway, ranging from 63 to 64% of Tcox in the 2 older forests to 94 % of Tcox in the 6 yr old stand. Budget calculations suggest that most of the O2 flux was associated with chemical oxidation in sediments of the 2 youngest forests. Sulfate reduction was the second most important diagenetic pathway (range 0.2 to 13.0 mm01 S m-' d-l) and, on average, total rates increased with increasing forest age. Manganese reduction appeared to be a minor decornposition pathway in all 3 stands (range 1.0 to 2.8 mm01 Mn m-' d-l), and iron reduction was measurable only in the 6 yr old forest (0.9 * 0.6 mm01 Fe m-' d-'). Denitrification was measurable only in the 35 yr old forest (2.2 i 0.5 mm01 N2 m-' d-l), but was the thud largest C oxidation pathway at this s~t e .Nitrogen fixation was most rapid in the 8 yr old forest (1425 i 468 pm01 NZ m-' d-l) and equivalent in the 6 yr old (245 + 127 pm01 N2 m-' d-l) and 35 yr old forests (444 * 92 pm01 NZ d-l). The molar carbon ratio of sediment respiration to forest net primary production (Rh,,,,JNPP) in the 6 and 35 yr old forests averaged 18 and 28 %, respectively. These comparatively low mineralization losses, coupled with the lack of measurable denitrification at 2 of the 3 plantations, imply that these R. apiculata plantations are highly efficient at sequestering labile carbon and nitrogen into plant biomass and sediment pools.

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“…Data from the Amazon River and Delta indicate that only one-fourth to one-third of the organic matter delivered to the Amazon Delta is buried (Showers and Angle, 1986;Aller et al, 1996;Keil et al, in press). The currently favored hypotheses for this low burial efficiency are that heterotrophic bacteria rapidly utilize organic matter by taking advantage of the recurrent redox oscillations in deltaic sediments, or that enhanced degradation of terrestrial organic matter occurs via co-metabolism of planktonic material introduced in the delta (Aller, 1994;Aller et al, 1996).…”

Section: Current Work In the Amazon Systemmentioning

confidence: 99%

Relationships between organic carbon preservation and mineral surface area in Amazon Fan (Holes 932A and 942A)

Keil¹,

Tsamakis²,

Wolf³

et al. 1997

Proceedings of the Ocean Drilling Program, 155 Scientific Results

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Mineral surface area (SA), neutral sugar (aldose) concentrations, and organic carbon content (OC) were measured in two holes from Ocean Drilling Program (ODP) Leg 155 (Holes 932A and 942A) and compared to analogues from the modern Amazon River and Delta. Nearly all (>90%) of the OC in the ODP holes was tightly associated with the mineral phase; the two phases could not be quantitatively separated after sonication and density fractionation. Organic matter in Holes 932A and 942A can thus be functionally defined as adsorbed. There is a relationship between OC and a sediment transport pathway prior to deposition. When OC is normalized to a mineral surface area (OC:SA), sediments that were rapidly deposited and strongly influenced by the river had average OC:SA ratios of 0.46 and 0.39 mgCm −2 for Holes 932A and 942A. Sediment deposited indirectly through nepheloid transport had lower OC:SA ratios (average 0.32 and 0.24 mgCm −2 ). For comparison, OC:SA ratios of suspended sediments from the Amazon River average 0.67 mgCm −2 , and modern Amazon Delta sediments have a loading of ~0.30 mgCm −2 . Although aldose concentrations in Hole 932A decreased downcore, corresponding molecular compositional patterns do not suggest extensive in situ diagenesis. Rather, the aldose composition throughout Hole 932 lithologic Subunits IIA and IIB is similar to that of fine suspended particulate materials carried by the modern Amazon River, which are largely composed of degraded material derived from plants and riverine microorganisms. The aldose data support isotopic and lignin compositional evidence for a terrestrial-riverine source of organic matter in Unit II of Hole 932A, as suggested by Goñi (this volume).

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Remineralization rates, recycling, and storage of carbon in Amazon shelf sediments

Cited by 245 publications

References 73 publications

Oxic/anoxic oscillations and organic carbon mineralization in an estuarine maximum turbidity zone (The Gironde, France)

Oxic/anoxic oscillations and organic carbon mineralization in an estuarine maximum turbidity zone (The Gironde, France)

Benthic decomposition rates and pathways in plantations of the mangrove Rhizophora apiculata in the Mekong delta, Vietnam

Relationships between organic carbon preservation and mineral surface area in Amazon Fan (Holes 932A and 942A)

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