Caesium distribution in northwest Mediterranean seawater, suspended particles and sediments

Calmet, D.; Fernandez, Jean-Michel

doi:10.1016/0278-4343(90)90066-u

Cited by 50 publications

(33 citation statements)

References 33 publications

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“…14) shows a positive pattern in the close vicinity of the Rhone River mouth extending over 30 km until 200 m depth. The prodelta region is the main deposition area of terrestrial POC in the model, which is in agreement with numerous previous studies (Calmet and Fernandez, 1990;Durrieu de Madron et al, 2000;Tesi et al, 2007). On the contrary, one could expect that such positive influence of terrestrial POM inputs on POC deposition would concern the entire Gulf of Lions.…”

Section: Influence Of Terrestrial Pom Inputs On Poc Depositionsupporting

confidence: 91%

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 Depositionsupporting

confidence: 91%

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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“…This feature matches the distribution footprint of the Rhône River inputs. Indeed, the South West has been proven to be a preferential direction for deposition of the terrestrial material in this area (Naudin et al, 1997;Calmet and Fernandez, 1990). Moreover, particles and organic matter tracers (radionuclides, carbon and nitrogen stable isotopes) from earlier studies clearly demonstrated a terrestrial origin of the sedimentary material nearby the river mouth (Aloisi et al, 1982;De Madron et al, 2000;Radakovitch et al, 1999b;Lansard et al, 2009;Tesi et al, 2007).…”

Section: Comparison Of In Situ and Ex Situ Diffusive Oxygen Uptake Ratesmentioning

confidence: 99%

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

et al. 2010

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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 O 2 m −2 d −1 ) and decrease offshore to values around 4.5 mmol O 2 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.Correspondence to: C. Cathalot (cecile.cathalot@lsce.ipsl.fr) 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 O 2 m −2 d −1 to values close to 10 mmol O 2 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.

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“…The sediment accumulation rate varies from 20 to 50 cm yr −1 at the present Roustan mouth of the Rhône River and strongly decreases with the distance from the river. Sediment is exported seaward by several turbid layers: the surface nepheloid layer, related to river plume; an intermediate nepheloid layer that forms during periods of water-column stratification; and a persistent bottom nepheloid layer, whose influence decreases from the river mouth to the outer shelf (Calmet and Fernandez, 1990;Naudin et al, 1997). The surficial plume is typically a few meters thick close to the mouth but rapidly thins seaward to a few centimeters (Millot, 1990); it is deflected southwestward by the surface water circulation on the GoL shelf.…”

Section: The Gulf Of Lions Geological and Oceanographic Settingsmentioning

confidence: 99%

Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt

et al. 2016

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Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are the most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea-land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m long sediment core from the Rhône mud belt in the Gulf of Lions in an area where the average accumulation rate is ca. 0.70 m 1000 yr −1 . This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multiproxy dataset (XRF core scan, 14 C dates, grain size and organic-matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes in the Rhône hydrological activity. Our results show that (1) the early Holocene was characterized by high sediment delivery likely indicative of local intense (but short-duration) rainfall events, (2) important sediment delivery around 7 ka cal BP presumably related to increased river flux, (3) a progressive increase in continental/marine input during the mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, (4) multidecadal to centennial humid events took place in the late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Ages Cold Period) and also coincide with time intervals of major floods in the northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

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Caesium distribution in northwest Mediterranean seawater, suspended particles and sediments

Cited by 50 publications

References 33 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

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

Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt

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