MICROHABITAT SELECTION OF BENTHIC FORAMINIFERA IN SEDIMENTS OFF THE RHONE RIVER MOUTH (NW MEDITERRANEAN)

2010 ◽  
Vol 40 (3) ◽  
pp. 231-246 ◽  
Author(s):  
M. Mojtahid ◽  
F. Jorissen ◽  
B. Lansard ◽  
C. Fontanier
Keyword(s):  
Benthic Foraminifera ◽  
River Mouth ◽  
Microhabitat Selection ◽  
Rhône River ◽  
Rhone River ◽  
Nw Mediterranean ◽  
Selection Of

scholarly journals Temporal variability of live (stained) benthic foraminiferal faunas in a river-dominated shelf – faunal response to rapid changes of the river influence (Rhône prodelta, NW Mediterranean)

2011 ◽  
Vol 8 (5) ◽  
pp. 9033-9086 ◽  
Author(s):  
A. Goineau ◽  
C. Fontanier ◽  
F. Jorissen ◽  
R. Buscail ◽  
P. Kerhervé ◽  
...  
Keyword(s):  
Organic Matter ◽  
Environmental Conditions ◽  
Spring Bloom ◽  
River Mouth ◽  
Rhône River ◽  
Faunal Composition ◽  
Wide Range ◽  
Rhone River ◽  
River Flood ◽  
Nw Mediterranean

Abstract. In the context of the French research project CHACCRA (Climate and Human-induced Alterations in Carbon Cycling at the River–seA connection), living (rose Bengal-stained) benthic foraminifera were investigated at two stations (24 and 67 m depth) in the Rhône prodelta (NW Mediterranean, Gulf of Lions). The aim of this study was to precise the response of benthic foraminiferal faunas to temporal changes of the Rhône River inputs (e.g. organic and terrigeneous material). Each site was sampled in April 2007, September 2007, May 2008 and December 2008, permitting to observe foraminiferal faunas of the 63–150 and >150 μm size fractions under a wide range of environmental conditions. Obvious variations in foraminiferal faunal composition were observed during the four investigated periods at the shallowest Station A located in the close vicinity of the Rhône River mouth. Different colonisation stages were observed after major Rhône River flood events, foraminiferal faunas responding with an opportunistic strategy few days to weeks after the creation of a peculiar sedimentary environment (Leptohalysis scottii, May 2008) or high amounts of organic matter supplied by a river flood (Ammonia tepida, December 2008). Under more stable conditions, relatively diverse and equilibrated faunas grew in the sediments. Species benefited from noticeable input of riverine phytodetritus to the sediment during spring bloom conditions (April 2007; e.g. Bolivina dilatata, Nonionella stella, Stainforthia fusiformis), or high amounts of still bio-available organic matter under more oligotrophic conditions (September 2007; e.g. Ammonia tepida, Psammosphaera fusca). The reduced influence of the Rhône River input at the farther Station N led to less contrasted environmental conditions during the four sampling periods, and so to less obvious variations in foraminiferal faunal composition. During reduced riverine influence (i.e. low Rhône discharge), species able to feed on fresh phytodetritus (e.g. Clavulina cylindrica, Hopkinsina atlantica, Nonionella iridea and Nonionella turgida) benefited from eutrophic conditions of the spring bloom (April 2007, May 2008). Conversely, the occurrence of Nouria polymorphinoides under oligotrophic conditions (September 2007, December 2008) was indicative of a benthic environment potentially disturbed by bottom currents. This study put into evidence the extremely rapid response of benthic foraminiferal faunas to strong variations in environmental conditions, especially close to the river mouth (Station A), response noticeably reduced farther from the mouth (Station N) due to a weaker impact of riverine input.

scholarly journals Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

2011 ◽  
Vol 8 (1) ◽  
pp. 549-592 ◽  
Author(s):  
L. Pastor ◽  
C. Cathalot ◽  
B. Deflandre ◽  
E. Viollier ◽  
K. Soetaert ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Continental Shelf ◽  
Carbon Mineralization ◽  
River Mouth ◽  
Total Carbon ◽  
Large Contribution ◽  
Organic Carbon Content ◽  
Rhône River ◽  
Rhone River

Abstract. In-situ oxygen microprofiles, sediment organic carbon content and pore-water concentrations of nitrate, ammonium, iron, manganese and sulfides obtained in sediments from the Rhône River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1) organic matter from the Rhône River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11–33 yr−1), (2) burial efficiency (burial/input ratio) in the Rhône prodelta (within 3 km of the river outlet) can be up to 80%, and decreases to ~20% on the adjacent continental shelf 10–15 km further offshore (3) there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates, (4) diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (>97%) and buried in the sediment, which leads to (5) a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River Ocean dominated Margins (RiOMar) environments.

scholarly journals Occurrence of perfluoroalkyl substances in the Bay of Marseille (NW Mediterranean Sea) and the Rhône River

2019 ◽  
Vol 149 ◽  
pp. 110491 ◽  
Author(s):  
Natascha Schmidt ◽  
Vincent Fauvelle ◽  
Javier Castro-Jiménez ◽  
Katixa Lajaunie-Salla ◽  
Christel Pinazo ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Perfluoroalkyl Substances ◽  
Rhône River ◽  
Rhone River ◽  
Nw Mediterranean ◽  
Nw Mediterranean Sea

scholarly journals Temporal variability of carbon recycling in coastal sediments influenced by rivers: assessing the impact of flood inputs in the Rhône River prodelta

2010 ◽  
Vol 7 (3) ◽  
pp. 1187-1205 ◽  
Author(s):  
C. Cathalot ◽  
C. Rabouille ◽  
L. Pastor ◽  
B. Deflandre ◽  
E. Viollier ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Continental Shelf ◽  
Spatial Pattern ◽  
River Mouth ◽  
Ex Situ ◽  
Rhône River ◽  
Reactive Material ◽  
Degradation Rates ◽  
Rhone River ◽  
The Impact

Abstract. River deltas are particularly important in the marine carbon cycle as they represent the transition between terrestrial and marine carbon: linked to major burial zones, they are reprocessing zones where large carbon fluxes can be mineralized. In order to estimate this mineralization, sediment oxygen uptake rates were measured in continental shelf sediments and river prodelta over different seasons near the outlet of the Rhône River in the Mediterranean Sea. On a selected set of 10 stations in the river prodelta and nearby continental shelf, in situ diffusive oxygen uptake (DOU) and laboratory total oxygen uptake (TOU) measurements were performed in early spring and summer 2007 and late spring and winter 2008. In and ex situ DOU did not show any significant differences except for shallowest organic rich stations. Sediment DOU rates show highest values concentrated close to the river mouth (approx. 20 mmol O2 m−2 d−1) and decrease offshore to values around 4.5 mmol O2 m−2 d−1 with lowest gradients in a south west direction linked to the preferential transport of the finest riverine material. Core incubation TOU showed the same spatial pattern with an averaged TOU/DOU ratio of 1.2±0.4. Temporal variations of sediment DOU over different sampling periods, spring summer and late fall, were limited and benthic mineralization rates presented a stable spatial pattern. A flood of the Rhône River occurred in June 2008 and delivered up to 30 cm of new soft muddy deposit. Immediately after this flood, sediment DOU rates close to the river mouth dropped from around 15–20 mmol O2 m−2 d−1 to values close to 10 mmol O2 m−2 d−1, in response to the deposition near the river outlet of low reactivity organic matter associated to fine material. Six months later, the oxygen distribution had relaxed back to its initial stage: the initial spatial distribution was found again underlining the active microbial degradation rates involved and the role of further deposits. These results highlight the immediate response of the sediment oxygen system to flood deposit and the rapid relaxation of this system towards its initial state (6 months or less) potentially linked to further deposits of reactive material.

scholarly journals Biogeochemical characterization of the riverine particulate organic matter transferred to the NW Mediterranean Sea

2014 ◽  
Vol 11 (1) ◽  
pp. 157-172 ◽  
Author(s):  
M. Higueras ◽  
P. Kerhervé ◽  
A. Sanchez-Vidal ◽  
A. Calafat ◽  
W. Ludwig ◽  
...  
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
High Water ◽  
Terrestrial Organic Matter ◽  
Rhône River ◽  
Δ13c And Δ15n ◽  
Coastal Rivers ◽  
Rhone River ◽  
Nw Mediterranean ◽  
Nw Mediterranean Sea

Abstract. A large amount of terrestrial organic matter is annually delivered by rivers to the continental shelf, where this material is either degraded, buried or transferred to the deep sea by hydrodynamic processes such as storms. The relative amount of terrestrial organic matter in the marine sediments is often determined by analysing the stable isotopes (δ13C and δ15N) and the C / N ratio of organic matter because the various particulate organic matter (POM) sources have distinct isotopic compositions. With the objective to refine and better interpret POM sources in the marine environment, we have characterized monthly terrestrial POM delivered by eight rivers discharging to the NW Mediterranean Sea: the Rhône, Hérault, Orb, Aude, Têt, Fluvià, Ter and Tordera rivers. These rivers were simultaneously sampled from November 2008 to December 2009 and the concentrations of total suspended matter (TSM), particulate organic carbon (POC) and nitrogen (PN), as well as their stable isotopic ratios (δ13C and δ15N) were determined. During the survey, three rainstorm events with winds coming from the E–NE and the S–SE impacted the NW Mediterranean. Depending on the direction of incoming winds, the fluvial response (amount of water discharge and TSM) was different. Rivers draining the Alps (Rhône River) and Central Massif (Hérault, Orb, and Aude rivers) were mostly impacted by rainstorms associated with winds coming from the S–SE, while rivers draining the Pyrenees (Têt, Fluvià, and Ter rivers) and the Montseny Massif (Tordera River) were impacted by rainstorms associated with winds coming from the E–NE. In addition, the spatial evolution of water discharges shows a different hydrological regime of the Rhône River, with relatively constant and high water stages and TSM concentrations when compared to coastal rivers, characterized by long periods of low water stages. TSM concentrations are positively correlated to water discharges (high water flows resuspended riverbed sediments) but show an inverse relationship with POC and PN relative contents (mostly due to dilution and by low availability of light in river waters during flood events). TSM in most of the coastal rivers have on average 2.5–3 times higher POC and PN mean contents than the Rhône River (8.5 and 1.5%, respectively, for coastal rivers compared to 3.6 and 0.5%, respectively, for the Rhône River). This discrepancy may be caused by the long drought periods in small coastal Mediterranean watersheds that enhance the eutrophication in studied coastal rivers. The δ13C ratios of organic matter also reflect this discrepancy between high and low water stages with values ranging from −33.2 to −24.5‰. The enriched 13C values (−26.3 ± 0.4‰ for the Rhône River and −26.9 ± 1.2‰ for coastal rivers), measured during high water stages, express mostly a mixture of terrestrial source (plant remains and soils) whereas depleted 13C values (∼ −30‰) associated with low water stages exhibit a source with predominant freshwater algae. The high δ15N mean values (>8‰) found in Têt, Ter and Tordera rivers may underline the importance of denitrification processes as a consequence of the eutrophication and anthropogenic impact.

scholarly journals Radionuclide deposition in the Rhône River Prodelta (NW Mediterranean sea) in response to the December 2003 extreme flood

2006 ◽  
Vol 234 (1-4) ◽  
pp. 179-189 ◽  
Author(s):  
J. Miralles ◽  
M. Arnaud ◽  
O. Radakovitch ◽  
C. Marion ◽  
X. Cagnat
Keyword(s):  
Mediterranean Sea ◽  
Rhône River ◽  
Extreme Flood ◽  
Rhone River ◽  
Nw Mediterranean ◽  
Nw Mediterranean Sea

scholarly journals Origin of remineralized organic matter in sediments from the Rhone River prodelta (NW Mediterranean) traced by Δ 14 C and δ 13 C signatures of pore water DIC

2018 ◽  
Vol 163 ◽  
pp. 112-122 ◽  
Author(s):  
Lara Pozzato ◽  
Jens Rassmann ◽  
Bruno Lansard ◽  
Jean-Pascal Dumoulin ◽  
Peter van Breugel ◽  
...  
Keyword(s):  
Organic Matter ◽  
Pore Water ◽  
Rhône River ◽  
Rhone River ◽  
Nw Mediterranean
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