Sediment cores for total mercury (Hg), monomethylmercury (MMHg), and total carbon (TC) were collected in the Southern Ocean and the South Sandwich Trench between 3 and 9 November 2022 during the PS133/1 expedition. Sampling depths ranged from approximately 3700 to 8000 m, using a multicorer (MUC) system. Total Hg concentrations were determined by thermal decomposition, amalgamation, and atomic absorption spectrophotometry (TDA–AAS) using a DMA-80 Direct Mercury Analyzer (Milestone). Monomethylmercury (MMHg) was analyzed by gas chromatography–cold vapor atomic fluorescence spectrometry (GC–CVAFS) following ethylation with sodium tetraethylborate on a KOH-digested aliquot, using a Brooks Rand manual system. Total carbon (TC) was measured using an elemental analyzer Euro EA 3000 (HEKAtech GmbH).