Microplastics analysis performed on micronekton organisms collected during the ABRACOS 2 survey in the Tropical Western Atlantic (3°S–9°S)

This dataset presents microplastic occurrence data from the digestive tracts of micronekton organisms collected during the ABRACOS 2 survey. Specimens were obtained primarily from micronekton trawls, with the exception of three individuals collected during mesopelagic trawl operations. Prior to microplastic analysis, morphometric measurements were recorded for each individual, including total length, standard length, jaw size, eye size, and lantern size, where applicable. All lengths are expressed in millimetres and weights in grams. Total wet weight and gastrointestinal tract wet weight were also recorded. Basic sampling metadata, including trawl start and end positions, trawl start and end times, sampling depth, temperature, dissolved oxygen, and salinity, are provided where available. Because specific field-level precautions against airborne microplastic contamination were not implemented during the cruise, additional quality assurance and quality control (QA/QC) procedures were applied in the laboratory. These included the use of 100% cotton lab coats and disposable gloves in a dedicated, cleaned room with limited personnel flow throughout the analysis process. All solutions were filtered through 47 mm GF/F glass fibre filters (0.7 µm pore size, Whatman) using a vacuum pump system equipped with laboratory glassware. All procedures were conducted under a laminar flow cabinet to further reduce exposure to airborne contamination. Specimens were carefully rinsed with filtered distilled water to remove particles attached to external tissues. Gastrointestinal tracts, including the stomach and intestine, were removed and rinsed with filtered distilled water. Prior to microplastic extraction, procedural blanks were conducted for each set of 5–10 samples. For each blank, a beaker was filled with 50 mL of sodium hydroxide (NaOH, 1 mol L⁻¹) solution, covered with a glass lid, and processed following the same protocol as the samples. Microplastics were extracted using alkaline digestion: each gastrointestinal tract was placed in a beaker and submerged in NaOH solution at a ratio of 1:100 (w/v), covered with a glass lid, and incubated at 60 °C for 24 h. Samples were homogenised during incubation and subsequently filtered through GF/F glass fibre filters (0.7 µm pore size) using a laboratory vacuum system. Filters containing digestion residues were placed in covered glass Petri dishes and oven-dried at 60 °C for 24 h. Particles retained on the filters were visually inspected under a stereomicroscope (Zeiss Stemi 508) coupled to a camera system (Axiocam 105 Color, Zeiss). Suspected microplastic particles were counted, photographed, and measured along their longest axis using Zeiss ZEN software. The visual detection limit was 0.02 mm (20 µm). Particles up to 5 mm in size were classified as microplastics and categorised by shape (fibres, fragments, films, foams, and beads) and colour (black, blue, green, red, and white). Taxonomic nomenclature follows the same WoRMS-based reference framework used throughout the dataset with AphiaIDs assigned whenever available. All variables are described in the README. The dataset includes 381 individuals, of which 268 contained at least one microplastic item and 113 showed no microplastic occurrence. A total of 661 microplastic items were recorded across all positive individuals.