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Auteur Soissons, L.M.; da Conceicao, T.G.; Bastiaan, J.; van Dalen, J.; Ysebaert, T.; Herman, P.M.J.; Cozzoli, F.; Bouma, T.J.
Titre Sandification vs. muddification of tidal flats by benthic organisms: A flume study Type Article scientifique
Année 2019 Publication Revue Abrégée Estuar. Coast. Shelf Sci.
Volume 228 Numéro Pages (down) Unsp-106355
Mots-Clés arenicola-marina; Benthic organisms; cerastoderma-edule bioturbation; Cerastorderma edule; community structure; erosion; impact; intertidal flat; lanice-conchilega; model; Ruditapes philippinarum; sediment erodability; Sediment properties; Silt content; Suspended sediment concentration; Tidal flats; wadden sea
Résumé Bioturbating benthic organisms have typically been characterised by how they modify the vertical sediment erosion thresholds. By means of several annular flume experiments, we aimed to understand how benthic organisms may affect grain-size sediment properties over time, and how this depends on the sediment type and the sediment loading of the water column. We compared the effect of two bioturbating macroinvertebrate species: a local dominant species, the cockle Cerastoderma edule and a spreading non-indigeneous species, the clam Ruditapes philippinarum. Our results indicate that the effect of benthic organisms on sediment dynamics is strongly dependent on both the prevailing environmental conditions and the benthic species present. If sediment is sandy, the benthos can gradually enhance the silt content of the sediment by mixing in part of the daily tidal sediment deposition. In contrast, if sediment is muddy, benthos can gradually decrease the silt content of the sediment by specifically suspending the fine fraction. Moreover, we observed that the native cockles had a stronger impact than invasive clams. Therefore, bioturbating benthos can have an important effect in determining the local sediment properties, with the outcome depending both on the species in question and the environmental conditions the bioturbator lives in. Our findings show that sediment bioturbation may have strong implications for tidal flat stability undergoing major changes from natural or anthropogenic sources.
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Volume de collection Numéro de collection Edition
ISSN 0272-7714 ISBN Médium
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Notes WOS:000496611500001 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2662
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Auteur Cousin, X.; Batel, A.; Bringer, A.; Hess, S.; Begout, M.-L.; Braunbeck, T.
Titre Microplastics and sorbed contaminants – Trophic exposure in fish sensitive early life stages Type Article scientifique
Année 2020 Publication Revue Abrégée Mar. Environ. Res.
Volume 161 Numéro Pages (down) 105126
Mots-Clés Artemia; benzo[a]pyrene; chemicals; cyp1a induction; Fish; fresh-water ecosystems; ingestion; Larvae; Marine medaka; Microplastics; mytilus-edulis l.; north-sea; Paramecium; pcbs; persistent organic pollutants; resin pellets; Trophic transfer; zebrafish; Zebrafish
Résumé The present study evaluated very small microplastic particle (MPs) transfer to zebrafish and marine medaka larvae via prey experimentally exposed to MPs from the onset of feeding. Larvae were fed Paramecium or Anemia nauplii loaded with fluorescent 1-5 or 10-20 mu m MP. Pollutant accumulation was analyzed by optically tracking of benzo[a]pyrene (BaP) and recording cyp1a transcription. Paramecium transferred 1-5 mu m particles only, whereas Artemia efficiently transferred both MPs. Although zebrafish and medaka larvae fed from the onset of active food intake (2-3 dph, respectively) on Paramecium and from days 6-7 post-hatch on Artemia nauplii, neither MP accumulation nor translocation to tissues was detected. MP egestion started within few hours after ingestion. Cyp1a induction and fluorescent analyses proved BaP bioavailability after transfer via Paramecium and Artemia. Unicellular or plankton organisms ingest contaminants via MPS and transfer effectively these to sensitive early life-stages of vertebrates, giving rise to whole-life exposure.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0141-1136 ISBN Médium
Région Expédition Conférence
Notes WOS:000579495700050 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2893
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Auteur Vianello, P.; Ternon, J.-F.; Demarcq, H.; Herbette, S.; Roberts, M.J.
Titre Ocean currents and gradients of surface layer properties in the vicinity of the Madagascar Ridge (including seamounts) in the South West Indian Ocean Type Article scientifique
Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 176 Numéro Pages (down) 104816
Mots-Clés agulhas current; biology; bloom; Chlorophyll-a; communities; dipoles; Eddy kinetic energy; fauna; Geostrophic currents; Madagascar Ridge; mesoscale eddies; Mixed layer depth; retroflection; Sea surface temperature; Seamounts; South West Indian Ocean; terms; variability; Walters shoal
Résumé This work is part of the MADRidge Project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the South West Indian Ocean: one here named MAD-Ridge (240 m below the surface) plus Walters Shoal (18 m) on the Madagascar Ridge, and La Perouse (60 m) on the abyssal plain east of Madagascar. The three span latitudes 20 degrees S and 33 degrees S, some 1500 km. The study provides the background oceanography for the once-off, multidisciplinary snapshot cruise studies around the seamounts. As life on seamounts is determined by factors such as summit depth, proximity to the light layers of the ocean, and the ambient circulation, a first description of regional spatial-field climatologies (16-22 years) and monthly along-ridge gradients of surface wind (driving force), water column properties of sea surface temperature, mixed layer depth, chlorophyll-a and eddy kinetic energy, plus ocean currents is provided. Being relevant to many applications in the study domain, these properties in particular reveal contrasting environments along the Madagascar Ridge and between the three seamounts that should drive biological differences. Relative to the other two seamounts, MAD-Ridge is in the more extreme situation, being at the end of the East Madagascar Current, where it experiences sturdy, albeit variable, currents and the frequent passing of mesoscale eddies.
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Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0967-0645 ISBN Médium
Région Expédition Conférence
Notes WOS:000556810400013 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2859
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Auteur Roberts, M.J.; Ternon, J.-F.; Marsac, F.; Noyon, M.; Payne, A.I.L.
Titre The MADRidge project: Bio-physical coupling around three shallow seamounts in the South West Indian Ocean Type Article scientifique
Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 176 Numéro Pages (down) 104813
Mots-Clés Biological productivity; biology; Current-topography interaction; dipoles; fisheries; Fisheries and governance; Foodweb; humpback whales; hypothesis; La Perouse; madagascar; Madagascar Ridge; seabird community; Seamounts; tuna; upwelling cell; variability; Walters Shoal
Résumé Compared with other ocean basins, little is known scientifically about the seamounts in the Indian Ocean. Nonetheless, fishers have plundered these fragile ecosystems for decades, and now mining is becoming a reality. We introduce a multidisciplinary project referred to as MAD-Ridge that recently focused on three shallow seamounts in the South West Indian Ocean between 19 degrees S and 34 degrees S. The larger Walters Shoal (summit at 18 m) discovered in 1963 occupies the southern part of the Madagascar Ridge and has long received attention from the fishing industry, and only recently by scientists. In contrast, nothing is known of the northern region of the ridge, which is characterised by a prominent, steep-sided seamount that has a flat circular summit at 240 m and width of similar to 20 km. This seamount is some 200 km south of Madagascar and unnamed; it is referred to here as the MAD-Ridge seamount. MAD-Ridge is the shallowest of a constellation of five deeper (>1200 m) seamounts on that part of the ridge, all within the EEZ of Madagascar. It lies in a highly dynamic region at the end of the East Madagascar Current, where mesoscale eddies are produced continuously, typically as dipoles. The Madagascar Ridge appears to be an area of great productivity, as suggested by the foraging behaviour of some tropical seabirds during chick-rearing and a longline fishery that operates there. The third seamount, La Perouse, is located between Reunion Island and Madagascar. With a summit 60 m below the sea surface, La Perouse is distinct from MAD-Ridge and Walters Shoal; it is a solitary pinnacle surrounded by deep abyssal plains and positioned in an oligotrophic region with low mesoscale activities. The overall aim of the MAD-Ridge project was to examine the flow structures induced by the abrupt topographies, and to evaluate whether biological responses could be detected that better explain the observed increased in fish and top predator biomasses. The MAD-Ridge project comprised a multidisciplinary team of senior and early career scientists, along with postgraduate students from France, South Africa, Mauritius and Madagascar. The investigation was based around three cruises using the French vessels RV Antea (35 m) and RV Marion Dufresne (120 m) in September 2016 (La Perouse), November-December 2016 (MAD-Ridge) and May 2017 (Walters Shoal). This manuscript presents the rationale for the MAD-Ridge project, the background, a description of the research approach including the cruises, and a synopsis of the results gathered in the papers published in this Special Issue.
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Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0967-0645 ISBN Médium
Région Expédition Conférence
Notes WOS:000556810400012 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2856
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Auteur Annasawmy, P.; Ternon, J.-F.; Lebourges-Dhaussy, A.; Roudaut, G.; Cotel, P.; Herbette, S.; Menard, F.; Marsac, F.
Titre Micronekton distribution as influenced by mesoscale eddies, Madagascar shelf and shallow seamounts in the south-western Indian Ocean: an acoustic approach Type Article scientifique
Année 2020 Publication Revue Abrégée Deep-Sea Res. Part II-Top. Stud. Oceanogr.
Volume 176 Numéro Pages (down) 104812
Mots-Clés biological production; circulation; community composition; deep-scattering layer; diel vertical migration; Diel vertical migration; dynamics; Madagascar shelf; mesopelagic fish; Mesoscale eddies; Micronekton; mozambique channel; Multi-frequency; myctophid fishes; Seamount; South-western indian ocean; zooplankton
Résumé An investigation of the vertical and horizontal distributions of micronekton, as influenced by mesoscale eddies, the Madagascar shelf and shallow seamounts, was undertaken using acoustic data collected during two research cruises at an unnamed pinnacle (summit depth similar to 240 m) thereafter named “MAD-Ridge”, and at La Perouse seamount (similar to 60 m) in the south-western Indian Ocean. MAD-Ridge is located to the south of Madagascar, in an “eddy corridor”, known both for its high mesoscale activity and high primary productivity. In contrast, La Perouse is located on the outskirts of the Indian South Subtropical Gyre (ISSG) province, characterised by low mesoscale activity and low primary productivity. During the MAD-Ridge cruise, a dipole was located in the vicinity of the seamount, with the anticyclone being almost stationary on the pinnacle. Total micronekton acoustic densities were greater at MAD-Ridge than at La Perouse. Micronekton acoustic densities of the total water column were lower within the anticyclone than within the cyclone during MAD-Ridge. Micronekton followed the usual diel vertical migration (DVM) pattern, except within the cyclone during MAD-Ridge where greater acoustic densities were recorded in the daytime surface layer. The backscatter intensities were stronger at the 38 kHz than at the 70 and 120 kHz frequencies in the daytime surface layer at MAD-Ridge cyclonic stations. These backscatter intensities likely correspond to gas-filled swimbladders of epi- and mesopelagic fish actively swimming and feeding within the cyclone or gelatinous organisms with gas inclusions. Our findings evidenced that the distributions of micronekton and DVM patterns are complex and are influenced significantly by physical processes within mesoscale eddies. The mesoscale eddies' effects were dominant over any potential seamount effects at the highly dynamic environment prevailing at MAD-Ridge during the cruise. No significant increase in total micronekton acoustic densities was observed over either seamount, but dense aggregations of biological scatterers were observed on their summits during both day and night.
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Editeur Lieu de Publication Éditeur
Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 0967-0645 ISBN Médium
Région Expédition Conférence
Notes WOS:000556810400001 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2836
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