210Pb and Caesium Accumulation in the Rhône Delta Sediments

Radakovitch, Olivier; Charmasson, Sabine; Arnaud, Mireille; Bouisset, P.

doi:10.1006/ecss.1998.0405

Cited by 106 publications

(91 citation statements)

References 33 publications

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“…On the other hand, the 1986 Chernobyl fallout is used to date the most recent part of cores (Appleby 1991). A property of Cs is its high mobility in marine sediments, with a preferential downward diffusive transport in porewater (Radakovitch et al 1999). Despite the potential Cs mobility by diffusive transport, leading to the spreading of the Cs peak, we can see in Figure 2 that the 137 Cs profile shows a clear maximum corresponding to 1963.…”

Section: Resultsmentioning

confidence: 99%

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

et al. 2010

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ABSTRACT.To obtain a precise radiocarbon Holocene chronology in coastal areas, it is necessary to estimate the modern 14 C reservoir age R(t) and its possible variations with time in relation to paleoenvironmental changes. The modern reservoir 14 C age was estimated by comparing AMS 14 C ages of 2 recent mollusk shells found in sediment cores sampled in the Palavasian lagoonal system (south of France) with ages derived from 210 Pb and 137 Cs data and historical accounts of identifiable storm events. The calculated modern R(t) value of 943 ± 25 14 C yr is about 600 yr higher than the global mean sea surface reservoir age. This high value, probably due to the relative isolation of the lagoon from marine inputs, is in good agreement with other R(t) estimates in Mediterranean lagoonal systems (Zoppi et al. 2001;Sabatier et al. 2008). 14 C ages were also obtained on a series of Holocene mollusk shells sampled at different depths of the ~8-m-long core PB06. Careful examination of the 14 C ages versus depth relationships suggests that R(t) in the past was lower and similar to the value presently measured in the Gulf of Lion (618 ± 30 14 C yr, Siani et al. 2000). The change in R(t) from 618 to 943 yr is thought to result from final closure of the coastal lagoon by the sandy barrier, due to the along-shore sediment transfer.

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Section: Resultsmentioning

confidence: 99%

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

et al. 2010

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“…Major microbial players in deltaic environment are known chemoorganotrophic bacteria belonging to the phyla Bacteroidetes, Actinobacteria and Planctomycetes as well as sulfateoxidizing bacteria, sulfate reducers and nitrifiers (Madrid et al, 2001;Aller and Aller, 2004;Madrid et al, 2006). The microbial community from sediments of the Rhô ne River prodelta (NW Mediterranean Sea) has never been described, but the high deposition and sedimentation rates (Radakovitch et al, 1999;Miralles et al, 2006), high oxygen consumption and high remineralization rates (Lansard et al, 2008;Cathalot et al, 2010;Pastor et al, 2011) suggest the presence of communities similar to the ones found in other dynamic deltaic environments.…”

Section: Introductionmentioning

confidence: 99%

River organic matter shapes microbial communities in the sediment of the Rhône prodelta

et al. 2014

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Microbial-driven organic matter (OM) degradation is a cornerstone of benthic community functioning, but little is known about the relation between OM and community composition. Here we use Rhô ne prodelta sediments to test the hypothesis that OM quality and source are fundamental structuring factors for bacterial communities in benthic environments. Sampling was performed on four occasions corresponding to contrasting river-flow regimes, and bacterial communities from seven different depths were analyzed by pyrosequencing of 16S rRNA gene amplicons. The sediment matrix was characterized using over 20 environmental variables including bulk parameters (for example, total nitrogen, carbon, OM, porosity and particle size), as well as parameters describing the OM quality and source (for example, pigments, total lipids and amino acids and d 13 C), and molecular-level biomarkers like fatty acids. Our results show that the variance of the microbial community was best explained by d 13 C values, indicative of the OM source, and the proportion of saturated or polyunsaturated fatty acids, describing OM lability. These parameters were traced back to seasonal differences in the river flow, delivering OM of different quality and origin, and were directly associated with several frequent bacterial operational taxonomic units. However, the contextual parameters, which explained at most 17% of the variance, were not always the key for understanding the community assembly. Co-occurrence and phylogenetic diversity analysis indicated that bacteria-bacteria interactions were also significant. In conclusion, the drivers structuring the microbial community changed with time but remain closely linked with the river OM input.

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“…Extensive studies about recent processes, sedimentation and circulation in the GoL, in particular related to the Grand Rhône river delta sediments have also 2 been published in the last years (Marty et al, 2001;Beaudouin et al, 2004;Petrenko et al, 2005;Estournel et al, 1997Estournel et al, , 2001Radakovitch et al, 1999;Thill et al, 2001). In the present paper we discuss the occurrence of shallow gas evidences in the recent sediments off the Grand Rhône prodelta.…”

Section: Introductionmentioning

confidence: 63%

“…Based on 210 Pb dating, the maximum accumulation rates estimated for the Grand Rhône delta sediments range from 40 cm/y at the top of the delta front to 0.2 cm/y on the continental shelf, decreasing rapidly seawards with preferential S-SW direction from the mouth in relation to the spreading of surface and bottom nepheloid layers in the area (Radakovitch et al, 1999). In a broader study in the GoL, Miralles et al (2005) The model shows flood-related sedimentation mainly localized off the river mouth, having the maximum sedimentation (more than 2 m) in the closest area to the Grand Rhône, which corresponds with areas where the high methane content is found in our samples.…”

Section: Introductionmentioning

confidence: 99%

Shallow gas off the Rhône prodelta, Gulf of Lions

et al. 2006

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In areas unaffected by the high flux of organic matter and rapid/thick flood deposition, or in between flood events, the conditions for methanogenesis and gas accumulation have not been met. In these areas, the physical and biological reworking of the surficial sediment may effectively oxidize and mineralize organic matter and limit bacterial methanogenesis in the subsurface. We propose that in the Rhône prodelta flood deposits deliver significant amounts of terrigenous 1 organic matter that can be rapidly buried, effectively removing this organic matter from aerobic oxidation and biological uptake, and leading to the potential for methanogenesis with burial.

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210Pb and Caesium Accumulation in the Rhône Delta Sediments

Cited by 106 publications

References 33 publications

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

Holocene Variations of Radiocarbon Reservoir Ages in a Mediterranean Lagoonal System

River organic matter shapes microbial communities in the sediment of the Rhône prodelta

Shallow gas off the Rhône prodelta, Gulf of Lions

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