Carbon inputs of the Rhône River to the Mediterranean Sea: Biogeochemical implications

Sempéré, Richard; Charrìère, Bruno; Wambeke, F. Van; Cauwet, Gustave

doi:10.1029/1999gb900069

Cited by 186 publications

(193 citation statements)

References 60 publications

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“…12a and c), which can be explained by the linear dependence between Rhone River runoffs and terrestrial POC inputs in the model (Sempéré et al, 2000). Terrestrial inputs appear responsible for a net 20 % maximum increase of the total POC deposition at the whole shelf scale (Fig.…”

Section: Influence Of Terrestrial Pom Inputs On Poc Depositionmentioning

confidence: 99%

“…Particulate organic carbon (POC) inputs were estimated from an empirical linear relationship evidenced with Rhone River runoffs (Sempéré et al, 2000), and arbitrarily partitioned between small and large-sized particles considering a domination of dead microalgae (respectively, 90 % and 10 % of total). Particulate organic nitrogen (PON) and phosphorus (POP) inputs were then deduced considering average constant ratios POC:PON = 11.3 (±6.6) and POC:POP = 106.9 (±68.6) measured in the Rhone River in (P. Raimbault, personal communication, 2009).…”

Section: Rhone River Inputsmentioning

confidence: 99%

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Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

et al. 2011

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Abstract.A coupled hydrodynamic-biogeochemical modelling is developed to address main mechanisms that drive the particulate organic carbon (POC) deposition in the Gulf of Lions (NW-Mediterranean). Low-salinity water (LSW, salinity <37.5) lenses detached from the Rhone River plume under specific wind conditions tend to favour the biological productivity and provide a good opportunity for validating a planktonic ecosystem modelling. A specific calibration dedicated to river plume ecosystems is then proposed and validated using in situ measurements within such LSW lens (BIOPRHOFI cruise -May 2006) and on the Gulf of Lions. During spring 2006, the POC deposition is maximal on the prodelta area and within the coastal area in the Gulf of Lions. Organic detritus mostly contribute to the total POC deposition (82-92 %) whereas the contribution of living organisms (microphytoplankton) appears lower than 17 %. Exploring both influences of terrestrial inputs from the Rhone River and planktonic ecosystems on the POC deposition on the shelf, we estimated that the contribution of terrestrial POM inputs to the total POC deposition is lower than 17 % at the shelf scale during the study period, with maxima during peak discharges of the Rhone River. The main deposition area of terrestrial POC is found in the vicinity of the river mouth in agreement with sediment data. On the other hand, a remarkable influence of marine biological processes on the POC deposition is highlighted further on the shelf (from 60 to 80 m depth). A tight feedback between zooplankton and POM contents in the water column is proposed to explain Correspondence to: P. A. Auger (pierre-amael.auger@aero.obs-mip.fr) the control of POC deposition by zooplankton: terrestrial POM inputs would favour the development of living organisms through photosynthesis and grazing processes increasing the retention of organic matter within the food web. By favouring the development of large-sized zooplankton, LSW lenses may have paradoxically a negative impact on the carbon deposition on the shelf. In the same way, peak discharges of the Rhone River finally increase the gradient of POC deposition between the prodelta and the offshore area in the Gulf of Lions. The biogenic elements from the Rhone River are then exported further offshore through advection of zooplankton communities on the Gulf of Lions shelf.

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Section: Influence Of Terrestrial Pom Inputs On Poc Depositionmentioning

confidence: 99%

Section: Rhone River Inputsmentioning

confidence: 99%

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

et al. 2011

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“…With a mean annual discharge of 1700 m 3 s À 1 (Pont, 1997;Sempéré et al, 2000), the Rhô ne River represents an important input of freshwater and organic carbon to the Mediterranean Sea. Material deposited in the immediate vicinity of the river mouth forms a muddy sand bar, and as a result of sediment remobilization and displacement by waves and currents (Marion et al, 2010), the fine-grain prodelta sediments cover an area of 50 km 2 (Lansard et al, 2009) of the inner shelf.…”

Section: Study Site and Sampling Proceduresmentioning

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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“…2). POC expressed as a percentage of SPM ranged from 0.8 to 11.6 %, and tends to be lower when water flows are highest (Sempéré et al, 2000) 3.2 Use of lipid tracers to estimate the composition and origin of POM collected in the Rhône River…”

Section: Water Discharge Suspended Particulate Matter (Spm) and Partmentioning

confidence: 99%

“…Based on various studies, the mean annual flux of suspended matter is about 6.7×10 6 t yr −1 over the period 1967(Eyrolle et al, 2012, and the annual particulate organic carbon (POC) flux was estimated to be 1.94 ± 1.09 × 10 5 t yr −1 (Sempéré et al, 2000). The labile POC fraction, calculated as the carbon contribution from sugars and amino acids to Total POC, was estimated to be between 3 and 27 % depending on the amount of SPM (Sempéré et al, 2000). The Rhône River represents 14 and 10 % of fresh water and particulate carbon input to the Mediterranean Sea, respectively (Ludwig et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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Abstract. Lipid tracers including fatty acids, hydroxyacids, n-alkanols, sterols and triterpenoids were used to determine the origin and fate of suspended particulate organic matter (POM) collected in the Rhône River (France). This seasonal survey (April 2011 to May 2013) revealed a yearround strong terrestrial higher-plant contribution to the particulate organic matter (POM), with significant algal inputs observed in March and attributed to phytoplanktonic blooms likely dominated by diatoms. Major terrigenous contributors to our samples are gymnosperms, and more precisely their roots and stems, as evidenced by the presence of high proportions of ω-hydroxydocosanoic acid (a suberin biomarker). The high amounts of coprostanol detected clearly show that the Rhône River is significantly affected by sewage waters.Specific sterol degradation products were quantified and used to assess the part of biotic and abiotic degradation of POM within the river. Higher-plant-derived organic matter appears to be mainly affected by photo-oxidation and autoxidation (free radical oxidation), while organic matter of mammal or human origin, evidenced by the presence of coprostanol, is clearly more prone to bacterial degradation. Despite the involvement of an intense autoxidation-inducing homolytic cleavage of peroxy bonds, a significant proportion of hydroperoxides is still intact in higher plant debris. These compounds could affect the degradation of terrestrial material by inducing an intense autoxidation upon its arrival at sea.

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Carbon inputs of the Rhône River to the Mediterranean Sea: Biogeochemical implications

Abstract: Abstract. Since the damming of the Nile, the Rh6ne River is the main freshwater and sediment supplier to the Mediterranean Sea. We estimated for the period 1987-1996, the dissolved and particulate organic carbon (DOC and POC), dissolved inorganic carbon (DIC), and total suspended matter (

Cited by 186 publications

References 60 publications

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

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

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

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