seanoe:99990 Schmidt Sabine CNRS 2025-02-11 ISO 19115:2003/19139 1.0 Distribution of 210Pb, 226Ra, 228Th and K in tidal flat sediments of Arcachon Bay 2025-02 2025-02-11 Schmidt Sabine (2025). Distribution of 210Pb, 226Ra, 228Th and K in tidal flat sediments of Arcachon Bay. SEANOE. https://doi.org/10.17882/99990 The Arcachon Bay is a unique and ecologically important meso-tidal lagoon on the Atlantic coast of south-west France. The Arcachon Bay has the largest area of dwarf seagrass (Z. noltei) in Europe, the extent of which was stable in their extent between the 1950s and 1990s, but a decline in seagrass was observed in mid-2000. The decline of Zostera (seagrass) may have a significant impact on sedimentation in this coastal ecosystem rich in marine life. Interface cores were collected in September 2022 to determine sediment and mass accumulation rates (SAR, MAR) in the Arcachon Bay. Ten study areas were selected, distributed over most of the areas where seagrass meadows are actually observed. Two sites were visited each time, one with the presence of Zostera noltei in good condition (Healthy) and the other where the sediment was bare (Bare). Maximum water heights during spring tides range from 3.44 m for the deepest site (Garrèche) to 2.09 m for the shallowest site (Fontaines). A total of 20 sediment cores were sampled and carefully extruded every 1 cm from the top to the bottom of the core. The sediment layers were used to determine dry bulk density and selected radioisotope activities: DBD, 210Pb, 226Ra, 137Cs, 228Th and 40K expressed as %K).  The measurements were funded half by the EU H2020 Green Deal REST-COAST project and half by Sabine Schmidt from her own resources. Schmidt Sabine CNRS SEANOE https://www.seanoe.org/data/00888/99990/illustration.gif Core sampling of the mudflats in Arcachon Bay in September 2022 Arcachon Bay tidal flat sediment Dry Bulk Density 210Pb 226Ra 228Th K Marine geology H2020 REST-COAST (Agreement: 101037097) Geology ODATIS aggregation parameters and Essential Variable names 2024-09-16 geonetwork.thesaurus.external.theme.NVS.OD1 Marine geology SeaDataNet Parameter Disciplines 2021-04-07 geonetwork.thesaurus.external.parameter.NVS.P08 /Observational data/in-situ Type de jeux de donnée ODATIS 2024-10-15 geonetwork.thesaurus.local.theme.type_jeux_donnee CC-BY (Creative Commons - Attribution) oceans -1.3 -1.0 44.6 44.8 2022 CSV https://www.seanoe.org/data/00888/99990/ WWW:DOWNLOAD-1.0-link--download Quality controlled data Profiles of dry bulk density and selected radionuclides in tidal flats of the Arcachon bay [RESTRICTED] - 52 KB https://doi.org/10.17882/99990 WWW:LINK-1.0-http--metadata-URL DOI of the product https://www.seanoe.org/data/00888/99990/ rel-canonical Seanoe Dry bulk density (DBD) determination: water content was determined by weighing each sediment samples before and after drying at 60°C, and dry bulk density was subsequently calculated, assuming a mineral density of 2.65 g/cm. Radionuclide activities were measured using a high-efficiency, broad energy gamma detector equipped with a Cryo-Cycle II (Mirion). The gamma detector was calibrated using IAEA certified materials (RGU-1). Errors on activities are based on standard deviation counting statistics.