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Registros recuperados: 15
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A model of sediment transport under the influence of surface bioturbation: generalisation to the facultative suspension-feeder Scrobicularia plana ArchiMer
Orvain, Francis.
Flume experiments were designed to study how sediment erodibility was modified by the facultative suspension-feeder Scrobicularia plana living at different densities in sediment beds of various degrees of compaction. Two separate erosion phases were identified from the resuspension kinetics: (1) erosion of an unconsolidated surficial layer (i.e. fluff layer) and (2) the subsequent bed erosion. S. plana were found to influence both erosion phases: (1) erosion rates of the fluff layer were controlled by bioturbation activities, the extents of which were influenced by bivalve density and the degree of compaction of the sediments, and (2) critical thresholds of the subsequent bed erosion decreased as clam density increased, likely due to depressions in the...
Tipo: Text Palavras-chave: Resuspension; Model; Functional groups; Sediment transport; Bioturbation; Scrobicularia plana; Intertidal mudflat.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-3776.pdf
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Does the size of the microphytobenthic biofilm on intertidal muflats depend on the available photosynthetic biomass? ArchiMer
Herlory, Olivier; Blanchard, G; Planche, S; Huet, V; Richard, Pierre.
Many scientists consider that the top centimetre of the sediment on intertidal mudflats contains the photosynthetic competent biomass (PCB). Part of this biomass migrates upward to the surface of the sediment during diurnal emersion periods to form a temporary biofilm: the photosynthetic active biomass (PAB). The present study tests the hypothesis that the size of the biofilm (PAB) is functionally dependent on PCB. Therefore, we have plotted PAB as a function of PCB for a range of different environmental conditions: 3 seasons and 5 tidal situations, representing a total of 600 cores. This investigation points out that, in spring and autumn, there was a simple linear relationship between PAB and PCB, thus indicating that the maximum size of the biofilm...
Tipo: Text Palavras-chave: Functional relationship; Biofilm; Biomass; Intertidal mudflat; Microphytobenthos.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-3622.pdf
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Dynamic model of the short-term variability of microphytobenthic biomass on temperate intertidal mudflats ArchiMer
Guarini, Jean-marc; Blanchard, Gf; Gros, Philippe; Gouleau, Dominique; Bacher, Cedric.
In the present paper, we list and document the relevant behavioral and physiological processes controlling primary productivity of epipelic microalgae on intertidal mudflats in order to develop a simplified model. We first propose, in an attempt to characterize the 'photosynthetically active biomass' of the epipelic community, a new approach to describe the photic environment at the sediment surface, by substituting a discrete a-layer model in place of continuous vertical light distribution. This concept thus allows us to build a functional representation of the distribution of the photosynthetically active biomass in the sediment and, by then integrating the light and temperature forcing of the latter biomass, to predict the dynamics of the whole epipelic...
Tipo: Text Palavras-chave: Microphytobenthos; Intertidal mudflat; Primary production; Dynamic model; Migratory rhythm; Ecophysiological response.
Ano: 2000 URL: http://archimer.ifremer.fr/doc/00000/10540/7601.pdf
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Dynamics of spatial patterns of microphytobenthic biomass: inferences from a geostatistical analyisis of two comprenhensive surveys in Marennes-Oléron Bay (France) ArchiMer
Guarini, Jean-marc; Blanchard, Gerard; Bacher, Cedric; Gros, Philippe; Riera, Pascal; Richard, Pierre; Gouleau, Dominique; Galois, Robert; Prou, Jean; Sauriau, Pierre-guy.
Microphytobenthos plays an important role as primary producer in shallow embayments subject to a tidal regime. The present paper aims to characterize the spatial patterns of sedimentary chlorophyll a (chl a) biomass in 2 seasons in the wide intertidal mudflats of the Marennes-Oleron Bay (France); furthermore, it provides estimates of total microphytobenthic biomass. Accordingly, a systematic sampling scheme was performed in June 1995 and in January 1996. On average, biomass was higher in June (ca 120 mg chl a m-2) than in January (ca 85 mg chl a m-2). Moreover, the geostatistical analysis revealed that spatial similarities were propagated over larger distances in June (6 km) than in January (2.2 km). In order to account for this result , we suggest that...
Tipo: Text Palavras-chave: Marennes Oleron; Intertidal mudflat; Geostatistics; Spatial distribution; Chrlorophyll a; Microphytobenthos.
Ano: 1998 URL: https://archimer.ifremer.fr/doc/1998/publication-3820.pdf
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Dynamics of spatial patterns of microphytobenthic biomass: inferences from a geostatistical analysis of two comprehensive surveys in Marennes-Oleron bay (France) ArchiMer
Guarini, Jean-marc; Blanchard, Fabian; Bacher, Cedric; Gros, Philippe; Riera, P; Richard, P; Gouleau, D; Galois, R; Prou, Jean; Sauriau, Pg.
Microphytobenthos plays an important role as primary producer in shallow embayments subject to a tidal regime. The present paper aims to characterize the spatial patterns of sedimentary chlorophyll a (chl a) biomass in 2 seasons in the wide intertidal mudflats of the Marennes-Oleron Bay (France); furthermore, it provides estimates of total microphytobenthic biomass. Accordingly, a systematic sampling scheme was performed in June 1995 and in January 1996. On average, biomass was higher in June (ca 120 mg chi a m(-2)) than in January (ca 85 mg chi a m(-2)). Moreover, the geostatistical analysis revealed that spatial similarities were propagated over larger distances in June (6 km) than in January (2.2 km). In order to account or this result, we suggest that...
Tipo: Text Palavras-chave: Microphytobenthos; Chlorophyll a; Spatial distribution; Geostatistics; Intertidal mudflat.
Ano: 1998 URL: http://archimer.ifremer.fr/doc/00447/55852/58117.pdf
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Environmental and behavioural factors affecting activity in the intertidal gastropod Hydrobia ulvae ArchiMer
Orvain, Francis; Sauriau, Pierre-guy.
Laboratory microcosms were used to investigate the mud snail Hydrobia ulvac (Pennant) bioturbation activities and behavioural changes in response to snail density, algal food, sediment moisture content, light regime and water cover conditions. Density-dependent kinetics of bioturbated muddy areas were described by von Bertalanffy equations, which provided reliable estimates of mud surface covering rates by snail tracks (m(2) h(-1) snail(-1)), Snails need a wet habitat to be active either covered by seawater or by moving in fluid layers for low-tide conditions. Light and microphytobenthic biomass, which are less potent to affect snail activity, are positively interrelated to increase covering rates in the tested chl a concentrations within the range of 1 -...
Tipo: Text Palavras-chave: Modelling; Intertidal mudflat; Hydrobia ulvae; Environmental factors; Bioturbation; Behaviour.
Ano: 2002 URL: http://archimer.ifremer.fr/doc/2002/publication-3775.pdf
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Microstructure of microphytobenthic biofilm and its spatio-temporal dynamics in an intertidal mudflat (Aiguillon Bay, France) ArchiMer
Herlory, Olivier; Guarini, Jean-marc; Richard, Pierre; Blanchard, Gerard.
The spatio-temporal dynamics of the microphytobenthic biofilm was analysed at microscale over a complete day-time emersion period in an intertidal mudflat. The structures of the biofilm were monitored by analysing the variability of the epipelic diatom cover in the horizontal dimension and the kinetics of biomass dispersion in the vertical dimension. Colonisation of the sediment surface by diatoms was rapid (within 15 min); 75% of the biomass contained in the top 1 mm was concentrated in the upper 200 mum, but the cover never reached 100%. This biomass had a higher chlorophyll a/pheopigment ratio than deeper in the sediment, suggesting a better physiological state and a higher photosynthetic potential. The dynamics of the biomass in the upper 200 mum...
Tipo: Text Palavras-chave: Microphytobenthos; Biofilm; Intertidal mudflat; Spatio temporal dynamics; Microscale.
Ano: 2004 URL: http://archimer.ifremer.fr/doc/00000/10905/7580.pdf
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Modélisation de la dynamique du microphytobenthos des vasières intertidales du bassin de Marennes-Oléron. Effets des synchroniseurs physiques sur la régulation de la production ArchiMer
Guarini, Jean-marc.
The study aimed at quantifying the spatio-temporal evolution of microphytobenthic biomass in intertidal mudflats of Marennes-Oléron Bay. To reach this goal, a dynamic model has been proposed, including processes of primary production, active migration of epipelic diatoms and biomass lasses due to mortalities on one hand and resuspension in the water column during submersion on the other hand. The spatialisation is given by a hydrodynamic madel which calculates the water height everywhere. The photic environment of microphytobenthos is described in a discrete way, by means of two layers: the biofilm of epipelic algae « S »on the top of the sediment and the fust centimeter of the mud « F ». The endogenous vertical migration rhythm of epipelic algae controls...
Tipo: Text Palavras-chave: Microphytobenthos; Vasière intetidale; Modélisation; Dynamique de la biomasse; Expérimentation; Ecophysiologie; Couplage physique/biologie; Microphytobenthos; Intertidal mudflat; Modelling; Dynamics of the biomass; Experimentation; Ecophysiology; Physics/biology coupling.
Ano: 1998 URL: http://archimer.ifremer.fr/doc/00439/55029/56462.pdf
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Monthly HPLC measurements of pigment concentration from an intertidal muddy sediment of Marennes-Oléron Bay, France ArchiMer
Cariou-le Gall, Valerie; Blanchard, Gerard.
Chloropigments and carotenoids were measured by HPLC in an intertidal muddy sediment of Marennes-Oleron Bay (France). Concentrations were determined as a function of sediment depth at low tide. The analyses were carried out at monthly intervals over 1 yr. Pigment analysis indicated that the microphytobenthic community was dominated by diatoms throughout the sampling year. Chlorophyll b was not encountered at any time or depth, indicating that no input from macrophytic detritus had occurred at the sampling site. There was a large pool of phaeopigments a, of which phaeophorbides were the major forms (75%). A microphytobenthic bloom occurred between March and June during which phaeopigments significantly increased with a high proportion of phaeophorbides...
Tipo: Text Palavras-chave: Pigment; HPLC; Intertidal mudflat; Microphytobenthos; Seasonal change.
Ano: 1995 URL: http://archimer.ifremer.fr/doc/00257/36844/36666.pdf
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Network analysis and inter-ecosystem comparison of two intertidal mudflat food webs (Brouage Mudflat and Aiguillon Cove, SW France) ArchiMer
Leguerrier, D; Degre, Delphine; Niquil, N.
Network analysis was used to analyse steady-state models of the food webs of two intertidat mudflat ecosystems: Aiguillon Cove and Brouage Mudflat, on the South-Western Atlantic Coast of France. The aim was to highlight emergent properties of food-web functioning in these two ecosystems and to compare these properties with other coastal ecosystems. Both ecosystems imported detritus in parallel to a high benthic primary production. They were characterised by a high diversity of resources. Both also exported living material, leading to a high quality production, quantified as export of Exergy. This export was mainly composed of cultivated bivalves during the cold season for Brouage Mudflat, and of the migration of grazing fish in Aiguillon Cove during the...
Tipo: Text Palavras-chave: Atlantic coast; Intertidal mudflat; Network analysis; Inverse analysis; Ecosystem comparison; Food web.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3696.pdf
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Nutrient fluxes on an intertidal mudflat in Marennes-Oleron Bay, and influence of the emersion period ArchiMer
Feuillet-girard, Michelle; Gouleau, Dominique; Blanchard, Gérard; Joassard, Lucette.
Fluxes of nutrients (NH sub(4) super(+), NO sub(3) super(-), PO sub(4) super(3-) and Si(OH) sub(4)) were studied on an intertidal mudflat in Marennes-Oleron Bay, France, at two different seasons and at different times of the emersion period. Fluxes through the sediment-water interface were both calculated from vertical profiles of nutrient concentration in pore-water (diffusive fluxes, JD) and measured in light and dark benthic mini-chambers (measured fluxes, J sub(0)). Results indicate that ammonia was mainly released in summer while nitrate was mainly taken up in late winter. This uptake from the overlying water was probably due to the coupling of nitrification-denitrification within the sediment. The J sub(0) /J sub(D) ratio further indicates that...
Tipo: Text Palavras-chave: Estran vaseux; Flux de nutriments; Microphytobenthos; Bioturbation; Marennes-Oléron; Intertidal mudflat; Nutrient fluxes; Microphytobenthos; Bioturbation; Marennes-Oleron Bay.
Ano: 1997 URL: http://archimer.ifremer.fr/doc/00038/14893/12220.pdf
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Spatio-temporal structure of the epipelic diatom assemblage from an intertidal mudflat in Marennes-Oleron Bay, France ArchiMer
Haubois, Anne-gaelle; Sylvestre, F; Guarini, Jean-marc; Richard, Pierre; Blanchard, G.
Spatio-temporal changes in taxonomic composition and structure of an epipelic diatom assemblage from an intertidal mudflat on the French Atlantic coast was studied over an annual cycle along a cross-shore transect. The assemblage structure was described by estimating both relative abundance and contribution to biovolume of each species. Results showed that the assemblage was numerically dominated by small-sized species (mean relative abundance of 91%). Large species, however, significantly contributed to the total biovolume (mean contribution to biovolume of 49%). A factorial correspondence analysis indicated that the epipelic assemblage was relatively homogeneous along the cross-shore transect but emphasized the seasonal succession of diatom species. In...
Tipo: Text Palavras-chave: Cell volume; Assemblage structure; Species composition; Epipelic diatoms; Intertidal mudflat.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-3702.pdf
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Spatio-temporal variations in intertidal mudflat erodability: Marennes-Oleron Bay, western France ArchiMer
Orvain, Francis; Sauriau, Pierre-guy; Le Hir, Pierre; Guillou, Gael; Cann, Philippe; Paillard, Michel.
A portable erosion device (ERIS) was deployed in November 2000 and May 2001 to investigate the spatio-temporal variation of fine-grained sediment erosion over a transect on the intertidal mudflats of Marennes-Oleron Bay, western France. The objective was to relate changes in bed erodability over diurnal emersion periods to bioturbation, rapid changes in sediment characteristics, and microphytobenthos biomass. Macrofaunal assemblages were dominated by the bivalve, Scrobicularia plana, on the upper mudflat, and by the gastropod, Hydrobia ulvae. on the middle mudflat. A power relationship was obtained where tau(cr) was plotted as a function of sediment density. Results from the upper part of the mudflat deviated from this relationship due to bioturbation by...
Tipo: Text Palavras-chave: EPS; Microphytobenthos; Erodability; Intertidal mudflat; Sediment; Scrobicularia plana; Hydrobia ulvae; Bioturbation; Resuspension; Eris.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3779.pdf
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The effect of wave-induced turbulence on intertidal mudflats: Impact of boat traffic and wind ArchiMer
Verney, Romaric; Deloffre, J; Brun Cottan, J.-c.; Lafite, R.
Semi-diurnal and fortnightly surveys were carried out to quantify the effects of wind- and navigation-induced high-energy events on bed sediments above intertidal mudflats. The mudflats are located in the upper fluvial part (Oissel mudflat) and at the mouth (Vasiere Nord mudflat) of the macrotidal Seine estuary. Instantaneous flow velocities and mudflat bed elevation were measured at a high frequency and high resolution with an acoustic doppler velocimeter (ADV) and an ALTUS altimeter, respectively. Suspended particulate matter concentrations were estimated by calibrating the ADV acoustic backscattered intensity with bed sediments collected at the study sites. Turbulent bed shear stress values were estimated by the turbulent kinetic energy method, using...
Tipo: Text Palavras-chave: Seine Estuary; Intertidal mudflat; Bed erosion; Bed roughness length; Bottom shear stress; Boat waves; Wind waves.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2552.pdf
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Tidally-induced shear stress variability above intertidal mudflats in the macrotidal Seine estuary ArchiMer
Verney, Romaric; Brun Cottan, J; Lafite, R; Deloffre, J; Taylor, J.
Tidal currents and the spatial variability of tidally-induced shear stress were studied during a tidal cycle on four intertidal mudflats from the fluvial to the marine part of the Seine estuary. Measurements were carried out during low water discharge (< 400 m(3) s(-1)) in neap and spring tide conditions. Turbulent kinetic energy, covariance, and logarithmic profile methods were used and compared for the determination of shear stress. The c(TKE) coefficient value of 0.19 cited in the literature was confirmed. Shear stress values were shown to decrease above mudflats from the mouth to the fluivial part of the estuary due to dissipation of the tidal energy, from 1 to 0.2 N m-(2) for spring tides and 0.8 to 0.05 N m(-2) for neap tides. Flood currents...
Tipo: Text Palavras-chave: Seine estuary (France); Spatial variability; Neap spring conditions; Intertidal mudflat; Shear stress; Tidal currents.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1887.pdf
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