The ABRACOS dataset: a multidisciplinary marine ecosystem baseline for the western tropical Atlantic (2015–2017)

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Abstract. The western tropical Atlantic off Northeast Brazil is a dynamically complex region where major current systems contribute to interhemispheric exchanges, yet it remains one of the least observed ocean areas in terms of integrated, depth-resolved, and ecosystem-wide measurements. The two ABRACOS (Acoustics along the BRAzilian COaSt) surveys, conducted during austral spring 2015 (ABRACOS 1) and austral autumn 2017 (ABRACOS 2) aboard the R/V ANTEA, were designed to address this gap through coordinated multidisciplinary observations spanning the continental shelf, slope, seamounts, and open ocean along the Fernando de Noronha Ridge. Although each survey represents a synoptic seasonal snapshot, hydrographic and current observations from both campaigns have been shown to be representative of canonical spring and autumn conditions in the region. The dataset combines continuous underway measurements — thermosalinograph, ship-mounted ADCP, multifrequency active acoustics (38, 70, 120, and 200 kHz), and meteorological data — with station-based physical, biogeochemical, and biological sampling at 117 oceanographic stations. Station-based observations include 96 CTD-O₂ profiles, 881 discrete rosette bottle samples (salinity, dissolved oxygen, nutrients, pigments, cytometry, and phytoplankton abundance), 266 plankton net deployments, and 116 trawl operations targeting demersal and deep-pelagic communities from 10 to 1,100 m depth. Biological sampling yielded 172,241 taxonomically identified specimens representing 1,532 taxa across planktonic, nektonic, and demersal compartments. The dataset is further complemented by 3,466 stable isotope measurements (δ¹³C and δ¹⁵N) across particulate organic matter, zooplankton, and demersal and deep-pelagic organisms, as well as mercury concentrations and microplastic occurrence data for 194 and 381 individuals, respectively, collected during ABRACOS 2. All datasets are quality-controlled, harmonised across surveys using consistent station identifiers and taxonomic referencing against WoRMS and Eschmeyer's Catalog, and publicly archived in the SEANOE repository under dedicated DOIs. Having already supported more than 80 peer-reviewed publications across nine thematic domains — from physical oceanography and taxonomy to trophic ecology, anthropogenic contamination, and ecosystem connectivity — the ABRACOS dataset constitutes a unique multi-trophic, multi-compartment, and multi-contaminant baseline for the western tropical Atlantic, designed to support comparative analyses, ecosystem modelling, and synthesis efforts at regional to global scales. The datasets described in this paper are publicly available through SEANOE (https://www.seanoe.org).

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