Experimental study of the near-field impact of an oyster table on the flow

Kervella, Youen; Germain, Grégory; Gaurier, Benoît; Facq, Jean-Valéry; Cayocca, Florence; Lesueur, Patrick

doi:10.1016/j.euromechflu.2009.09.002

Cited by 14 publications

(22 citation statements)

References 12 publications

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“…This ecosystem is thus submitted to drastic changes in terms of current fields and mud accumulation in oyster-farming habitats (Ropert & Dauvin 2000, Kervella et al 2010. These sediments display a patchy an isotropic structure of mud.…”

Section: Resultsmentioning

confidence: 99%

“…3), the resulting spatial rearrangement of soft sediments is a factor determining the colonisation by benthic diatoms in intertidal systems. Oyster farming creates physical structures that contain different physical and chemical properties than surrounding sediments (Kervella et al 2010). The spatial patterns of silt content directly reflect mechanisms that are inevitably associated with an increase of organic matter that stimulates mineralisation processes and nutrient cycling.…”

Section: Discussionmentioning

confidence: 99%

“…The MPB cells (whose length ranges within the same spectrum of grain-size as silt) are able to settle with small particles during deposition processes and they find local conditions stimulating their growth. Oyster farms shape the landscape dynamics of intertidal systems where human activities have modified the current fields (Kervella et al 2010) and the spatial patterning of environmental factors profoundly alters the nature of species interactions and habitat occupation in several ways by favouring the development of MPB.…”

Section: Discussionmentioning

confidence: 99%

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Spatial and temporal interaction between sediment and microphytobenthos in a temperate estuarine macro-intertidal bay

Orvain¹,

Lefebvre²,

Montepini³

et al. 2012

Mar. Ecol. Prog. Ser.

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Intertidal flats of the estuarine macro-intertidal Baie des Veys (France) were investigated to identify spatial features of sediment and microphytobenthos (MPB) in April 2003. Gradients occurred within the domain, and patches were identified close to vegetated areas or within the oyster-farming areas where calm physical conditions and biodeposition altered the sediment and MPB landscapes. Spatial patterns of chl a content were explained primarily by the influence of sediment features, while bed elevation and compaction brought only minor insights into MPB distribution regulation. The smaller size of MPB patches compared to silt patches revealed the interplay between physical structure defining the sediment landscape, the biotic patches that they contain, and that median grain-size is the most important parameter in explaining the spatial pattern of MPB. Small-scale temporal dynamics of sediment chl a content and grain-size distribution were surveyed in parallel during 2 periods of 14 d to detect tidal and seasonal variations. Our results showed a weak relationship between mud fraction and MPB biomass in March, and this relationship fully disappeared in July. Tidal exposure was the most important parameter in explaining the summer temporal dynamics of MPB. This study reveals the general importance of bed elevation and tidal exposure in muddy habitats and that silt content was a prime governing physical factor in winter. Biostabilisation processes seemed to behave only as secondary factors that could only amplify the initial silt accumulation in summer rather than primary factors explaining spatial or long-term trends of sediment changes. KEY WORDS: Benthic diatoms · Benthos · Coastal ecosystems · Intertidal flats · Baie des Veys · Normandie · Spatial pattern · Geostatistics · KrigingResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 458: 53-68, 2012 Kronkamp 1999, Perissinotto et al. 2003). Dynamics of marine systems vary widely in their temporal and spatial components due to complexity in the benthopelagic coupling (Zajac 2008). The trophic environment of benthic fauna in these systems is therefore characterised by a high degree of spatial heterogeneity, such as transition zones and patches (Deegan & Garritt 1997, Dubois et al. 2007) that are related to the landscape of their habitats. It appears very relevant to understand the spatial patterns of primary producers in relation to sediment in order to elucidate the role they play in the trophic food web and to assess the respective contributions of both components to consumer's diet (Lefebvre et al. 2009). The questions of spatial distribution of benthic primary producer are thus critical to gain new insights in the dynamics and structure of macrozoobenthos that inhabit these environments (Herman et al. 2000).There is a general consensus that MPB biomass varies along wide-scale environmental gradients and is not affected by an isolated variable but, rather, depends on a combination of factors controlling ...

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Spatial and temporal interaction between sediment and microphytobenthos in a temperate estuarine macro-intertidal bay

Orvain¹,

Lefebvre²,

Montepini³

et al. 2012

Mar. Ecol. Prog. Ser.

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“…Coefficients of variation ranged between 5-20 %. In order to facilitate comparisons between Aber Benoît and Rivière d'Auray, the same scale was used for each study area circulation due to rearing structures has usually been reported to explain the enhanced sedimentation beneath cultures (Kervella et al 2010). In Aber Benoît, this phenomenon, associated with a relatively high density of oysters (39 tonnes per hectare), may have increased the sedimentation of fine particles beneath oysters in spite of the high current velocities generally occurring in this estuary (around 0.8-1.3 m s -1 ).…”

Section: Impact Of Oyster Culture On Grain Size and Organic Matter Pamentioning

confidence: 99%

Impact of Oyster Farming on Diagenetic Processes and the Phosphorus Cycle in Two Estuaries (Brittany, France)

et al. 2014

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This study aims to compare the impact of oyster cultures on diagenetic processes and the phosphorus cycle in the sediments of the Aber Benoît and the Rivière d'Auray, estuary of Brittany, France. Our results showed clear evidence of the seasonal impact of oyster cultures on sediment characteristics (grain size and organic matter parameters) and the phosphorus cycle, especially in the Aber Benoît. At this site, seasonal variations in sulfide and Fe concentrations in pore waters, as well as Fe-P concentrations in the solid phase, highlighted a shift from a system governed by iron reduction (Reference) to a system governed by sulfate reduction (beneath oyster). This could be partly explained by the increase in labile organic matter (i.e., biodeposits) beneath oysters, whose mineralization by sulfate led to high sulfide concentrations in pore waters (up to 4,475 lmol l -1 ). In turn, sulfide caused an enhanced release of phosphate in the summer, as adsorption sites for phosphate decreased through the formation of iron-sulfide compounds (FeS and FeS 2 ). In the Aber Benoît, dissolved Fe/PO 4 ratios could be used as an indicator of phosphate release into oxic water. Low Fe/PO 4 ratios in the summer indicated higher effluxes of phosphate toward the water column (up to 47 lmol m -2 h -1 ). At other periods, Fe/PO 4 ratios higher than 2 mol/mol indicated very low phosphate fluxes. In contrast, in the Rivière d'Auray, the occurrence of macroalgae, stranding regularly all over the site, clearly masked the impact of oyster cultures on sediment properties and the phosphorus cycle and made the use of Fe/PO 4 ratios more difficult in terms of indicators of phosphate release.

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“…Ce choix permet de considérer une immersion au réel de 4 m (valeur intermédiaire sur des estrans où elle peut varier entre 0 et 10 m), tout en conservant un nombre de configurations d'essais conséquent, la veine présentant une section d'essais de 4 m de large, 2 m de haut sur une longueur utile de 18 m. La structure ainsi réalisée (assemblage galvanisé de fer à béton de 8 mm de diamètre) présente une section de 0,5 m de large par 0,35 m de haut, pour une longueur finie de 7,2 m. Cette longueur ne permet pas de représenter une longueur de table réelle, mais est suffisante pour simuler les phénomènes en présence (KERVELLA et al, 2010) …”

Section: Approche Expérimentaleunclassified

Caractérisation numérique et expérimentale des perturbations engendrées par la présence de tables ostréicoles

Kervella¹,

Germain²,

Gaurier³

et al. 2010

XIèmes Journées, Les Sables d'Olonne

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Résumé :Sur de nombreux sites ostréicoles, d'importants mouvements sédimentaires modifient les conditions d'exploitation. Les mouvements naturels sont modifiés par la présence des tables à huîtres, les phénomènes en jeu étant de deux ordres : la perturbation des courants de marée et la modification des conditions de houle. Nous présentons dans ce document la méthodologie mise en place pour améliorer la compréhension des perturbations physiques du milieu engendrées par l'implantation de tables ostréicoles et caractériser les modifications de l'écoulement. Les résultats obtenus, tant expérimentaux que numériques, sont présentés et les développements pour une extension du modèle à l'échelle d'un parc ostréicole sont discutés. Des essais expérimentaux réalisés à l'échelle 1/2 ont notamment permis de caractériser l'impact en champ proche sur l'écoulement. Nous avons mis en évidence des zones préférentielles de dépôts de sédiments dues à l'interaction entre la couche limite se créant sur le dessous de la table et la couche limite de fond. Les contraintes de cisaillement mesurées près du fond ne sont quant à elles que très peu modifiées par la présence de la structure. Seule la contrainte de cisaillement sur l'ensemble de la colonne d'eau est amplifiée au passage des tables. Avec l'objectif de généraliser ces travaux, un modèle numérique a été développé à partir du code de CFD Fluent, les tables étant modélisées à l'aide de milieux poreux. La comparaison des résultats numériques et expérimentaux montre une bonne concordance : de 3 à 10% d'erreur moyenne sur l'ensemble du domaine d'étude suivant la configuration étudiée. Les choix effectués pour représenter la structure permettent d'envisager l'extension du modèle à des échelles plus importantes (plusieurs centaines de mètres) pour une structure seule ou en interaction avec d'autres placées en espace proche. Mots-clés :Mesures LDV -Essais expérimentaux -Simulations numériques -Contraintes de cisaillement -Hydrodynamique côtière - Table ostréicole 95 Thème 1 -Hydrodynamique côtière

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Experimental study of the near-field impact of an oyster table on the flow

Cited by 14 publications

References 12 publications

Spatial and temporal interaction between sediment and microphytobenthos in a temperate estuarine macro-intertidal bay

Spatial and temporal interaction between sediment and microphytobenthos in a temperate estuarine macro-intertidal bay

Impact of Oyster Farming on Diagenetic Processes and the Phosphorus Cycle in Two Estuaries (Brittany, France)

Caractérisation numérique et expérimentale des perturbations engendrées par la présence de tables ostréicoles

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