https://doi.pangaea.de/10.1594/PANGAEA.996264Rump, MarcoMarcoRump0009-0004-2329-4889Alfred Wegener Institute - Biological Institute HelgolandLannig, GiselaGiselaLannig0000-0002-9210-256XAlfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, BremerhavenBock, ChristianChristianBock0000-0003-0052-3090Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, BremerhavenBenthien, AlbertAlbertBenthien0000-0002-9159-3109Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, BremerhavenPogoda, BernadetteBernadettePogoda0000-0003-3997-426XAlfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, BremerhavenAntoni, DominikDominikAntoniAlfred Wegener Institute - Biological Institute HelgolandGerdts, GunnarGunnarGerdts0000-0003-0872-3927Alfred Wegener Institute - Biological Institute HelgolandSeawater carbonate chemistry, mortality, tissue trace metal and metabolomic data from a chronic ocean alkalinity enhancement exposure experiment with the European flat oyster Ostrea edulisPANGAEA2026ecotoxicologyocean alkalinity enhancementOstrea edulisMesocosm experiment2024-04-17T00:00:00/2025-03-12T00:00:00Bundled Publication of Datasets9 datasetsapplication/zipCreative Commons Attribution 4.0 InternationalData access is restricted (moratorium, sensitive data, license constraints)Adult European flat oysters (Ostrea edulis) were exposed in indoor mesocosms to two contrasting approaches for ocean alkalinity enhancement (OAE): dissolved alkalinity addition using NaOH and CaCl2, and olivine-based coastal enhanced silicate weathering, each targeting a total alkalinity increase of +250 or +500 µmol/kg over unamended seawater. An alkalinization phase (17 April to 19 June 2024) established the target total alkalinity in each treatment tank before oysters were introduced for a subsequent chronic exposure phase (8 May to 10 July 2024). Seawater pH and total alkalinity, salinity, temperature, dissolved oxygen, chlorophyll a, suspended particulate matter and ammonia were monitored throughout both phases, alongside oyster mortality. Full carbonate system parameters (CO2, HCO3-, CO32-, dissolved inorganic carbon, pCO2 and the aragonite and calcite saturation states) were calculated from the measured pH, total alkalinity, salinity and temperature using the seacarb package in R. At the end of the chronic exposure, oyster gill, mantle and hepatopancreas tissue was sampled for trace metal accumulation (nickel, chromium and cobalt) by ICP-OES, gill and mantle tissue for untargeted polar metabolite profiling by ¹H-NMR spectroscopy, and labial palps tissue for glycogen quantification. A separate short-term feeding experiment (12 to 21 November 2024) tested whether the shellfish diet used to feed the oysters (Reed Mariculture SD1800) contributes to the total alkalinity increase observed in the treatment tanks, independent of the OAE treatments. This submission bundles nine related data tables from this study; an individual, table-specific abstract accompanies each file in the file description.7.88894399999999754.18032700000003Helgoland, GermanyBundesamt für Naturschutzhttps://doi.org/10.13039/5011000104153522830300DEFINE2