Microplastics and POPs on the Southwestern Atlantic deep-sea floor: a study of megafauna and sediments

The deep sea is a historical sink for litter, but efforts to assess the human footprint in this ecosystem are relatively recent. Building upon previous works on the continental margins of the Southern Hemisphere, this study presents the first report of microplastics (MPs) and persistent organic pollutants (POPs) for the Southwestern Atlantic deep-sea floor. Ingestion of MPs by benthic invertebrates, and contamination by polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in demersal teleostean fish and sediments were recorded in the central Santos Basin, along the Brazilian continental slope, between 400 and 1503 m depth. Individuals from 9 invertebrate species (n = 61 organisms) had their gut content examined, with 3 species ingesting anthropogenic particles shaped like fibers (n = 23 fibers). The sea cucumber Deima validum was the most contaminated species, with 1.64 ± 0.70 fiber individual, and 54.54 % of individuals ingesting fibers. Five fibers were identified as MPs, composed of polyamide, polyacrylonitrile, polyaryletherketone, polystyrene and polysulfide synthetic rubber. Total PCBs in the fish (n = 14 organisms) ranged from 519 to 7636 ng g (lipid weight), and from 1.28 to 3.96 ng g (dry weight) in the sediments. Among the PBDEs investigated, only BDE-47 and BDE-99 were found, and only in the fish. While additional work is needed to ascertain the possible origin and ecological implications of MPs and POPs found at the bottom of the ocean, this study provides critical data on pollution levels for the deep-sea community of Southeastern Brazil.