title: Roles of regional hydrodynamic and trophic contamination in cadmium bioaccumulation by Pacific oysters in the Marennes-Oléron Bay (France).
abstract: The Marennes-Oléron Bay, hosting the largest oyster production in France, is influenced by the historic polymetallic pollution of the Gironde Estuary. Despite management efforts and decreasing emissions in the Gironde watershed, cadmium levels in oysters from the bay are close to the consumption limit (5 μg g(-1) dw, EC). From mid April to mid July 2009, we investigated the role of tidal resuspension and regional hydrodynamics on Cd speciation (seawater, SPM, phytoplankton, sediment, microphytobenthos) and bioaccumulation in 18 month-old oysters (gills, digestive glands, rests of tissues) reared under natural conditions (i) at ∼60 cm above the sediment and (ii) on the sediment surface. Dissolved and particulate Cd concentrations in surface and bottom waters were similar and constant over tidal cycle suggesting the absence of Cd release during sediment resuspension. Temporal dissolved and particulate Cd concentrations were closely related to Gironde Estuary water discharges, showing increasing concentrations during flood situations and decreasing concentrations afterwards. Cd depletion in the water column was associated with increasing Cd in the [20-100 μm] plankton fraction, suggesting Cd bioaccumulation. After 3 months, enrichment factors of Cd in tissues of oysters exposed in the water column and directly on the sediment were respectively 3.0 and 2.2 in gills, 4.7 and 3.2 in digestive glands and 4.9 and 3.4 in remaining tissues. Increasing Cd bioaccumulation in gills, digestive glands and remaining tissues can be related to elevated dissolved Cd in the bay, suggesting gill contamination via the direct pathway and subsequent internal redistribution of Cd to other organs and tissues. Elevated Cd contents in oysters reared on tables could be attributed to different trophic Cd transfer (phytoplankton versus microphytobenthos) or to different oyster metabolisms between the rearing conditions as suggested by metallothionein concentrations.
authors.affiliation: University of Bordeaux, UMR 5805 EPOC, GEMA Team, Avenue des Facultés, 33405 Talence, France. e.strady@epoc.u-bordeaux1.fr
authors.forename: Emilie
authors.initials: E
authors.lastname: Strady
authors.forename: Gérard
authors.initials: G
authors.lastname: Blanc
authors.forename: Magalie
authors.initials: M
authors.lastname: Baudrimont
authors.forename: Jörg
authors.initials: J
authors.lastname: Schäfer
authors.forename: Serge
authors.initials: S
authors.lastname: Robert
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafon
mesh_terms: D000818:Animals; D002104:Cadmium / Q000032:analysis / Q000378:metabolism*; D004784:Environmental Monitoring; D020387:Food Chain; D005602:France; D019015:Geologic Sediments / Q000737:chemistry; D005880:Gills / Q000378:metabolism; D010125:Ostreidae / Q000378:metabolism*; D010839:Phytoplankton / Q000378:metabolism; D012623:Seawater / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D014874:Water Pollutants, Chemical; D002104:Cadmium