Contaminação ambiental por microplásticos em Fernando de Noronha, Abrolhos e Trindade

Recently, the scientific community is focussed on the identification, characterization e quantification of microplastics, defined in the literature as those plastic particles with less than 5 millimetres. Microplastics are widespread on the ocean’s surface, on sand beaches and mud sediments, from the equator to the poles, on urban beaches and remote regions in the globe, and even deposited on deep sediments (>2,000m). Laboratory experiments indicate that organisms from every level of the marine food web potentially ingest microplastic particles. Organic, such as DDTs and PCBs, and inorganic pollutants available in seawater may adsorbed onto microplastics, transporting chemical contaminants to diverse regions in the globe, or being released in the gastrointestinal tract of vertebrates and invertebrates if ingested, when they are even transported along the marine food web. For more than 10 years, there were reports on the occurrence of microplastics in the North Pacific Ocean, mainly in the centre of the subtropical gyre, probably influenced by oceanographic variables. To the tropical Atlantic Ocean, however, evidences on the presence of microplastics were available only to sandy beaches in the Fernando de Noronha Archipelago (3°S, 32°W), and to waters around the Sao Pedro e Sao Paulo Archipelago. To fulfil this gap, microplastics were studied in three important insular environments in the western Atlantic Ocean: the Fernando de Noronha Archipelago, the Abrolhos Archipelago (17°S, 38°W) and the Trindade island (20°S, 29°W), during four scientific expeditions between December 2011 and March 2103. Floating plastics were collected by plankton tows (neuston) on the sea surface in the adjacent region to these environments. A total of 160 tows were conducted. In Trindade Island, more than 90% of the tows were contaminated with microplastics, identified as hard plastic fragments, soft fragments, paint chips, lines and fibres. In Fernando de Noronha and Abrolhos, approximately half of the tows were contaminated. Hard plastic fragments were the majority of the sampled items, as well as reported in other studies with plankton samples. Among plastic fragments, >75% had 5mm or less. The mean contamination pattern was 0.03 particles/m3, less than previously reported on the Pacific Ocean. Microplastics sampled on sediments were collected on sandy beaches in each island by quadrants dispoded in the strandline. Samples were also analysed in the relation to the main grain size of sediments because these information was still non-existent to the studied islands. In Abrolhos, no plastic particle was sampled. Hard plastic fragments and plastic pellets were identified in Fernando de Noronha and Trindade, where the windward side of the islans were significantly more contaminated when compared to the leeward side. These results are the first results indicating the occurrence of microplastic debris particles in the Western tropical Atlantic Ocean. The occurrence of microplastics highlights the vulnerability of these islands and their biota in relation to microplastic pollution.