Mercury concentration measurements performed on micronekton organisms collected during the ABRACOS 2 survey in the Tropical Western Atlantic (3°S–6°S)

This dataset compiles total mercury concentration measurements performed on micronekton organisms collected during the ABRACOS 2 survey in the tropical western Atlantic.  For each specimen, white muscle tissue was carefully excised and rinsed with distilled water to remove exogenous material such as scales, bones, or carapace fragments. For very small or gelatinous organisms, individuals of the same species were pooled when needed to obtain sufficient biomass for analysis. Samples were either oven-dried at 60 °C for 48 h or freeze-dried for 72 h, and then homogenised to a fine powder using a mortar and pestle. Total mercury concentrations were measured in approximately 50–100 mg of dried and homogenised tissue using thermal decomposition, gold amalgamation, and atomic absorption spectrophotometry with a DMA-80 analyser (Milestone, USA) at the Géosciences Environnement Toulouse laboratory (GET, Toulouse, France). Concentrations are reported on a dry weight basis in micrograms per gram (µg g⁻¹ dw), equivalent to parts per million (ppm). The analytical detection limit was 0.005 µg g⁻¹ dw. Analytical accuracy and precision were assessed using blanks and three certified reference materials: lobster hepatopancreas (TORT-3, certified THg: 0.29 ± 0.02 µg g⁻¹ dw), mussel tissue (NIST-2976: 0.06 ± 0.01 µg g⁻¹ dw), and freshwater sediment (PAC-2: 2.9 ± 0.3 µg g⁻¹ dw). Recovery rates were consistent with certified values within their reported uncertainties. Each record is associated with full taxonomic identification and, where available, station metadata. Taxonomic nomenclature follows the WoRMS-based reference framework, with AphiaIDs assigned whenever available.