Novaes, G.O.; Monteiro, S.M., and Rollnic, M., 2020. Microplastics in the fluvio-estuarine beaches of Cotijuba Island, Pará River estuary (Brazil). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 780–784. Coconut Creek (Florida), ISSN 0749-0208.
The coastal environment is constantly affected by materials of anthropogenic origin, among which are microplastics. Microplastics are particles smaller than 5 mm that are derived (or not) from the fragmentation of larger plastics. They are carried by currents and tides and deposited along the shoreline, and are mixed with the sediment. The aim of this study was to investigate the distribution of microplastics in depth within the sediment of five river-estuarine beaches located in Cotijuba Island, in the Pará River estuary (Brazil): PedraBranca, Vai-Quem-Quer, Flexeira, Farol, and Fazendinha. Sediment samples were collected at the high tide line and at three trenches on each beach, with 0.8 m depth, subdivided in four 0.2 m layers (0-20, 20-40, 40-60, 60-80 cm). Microplastics were present on all beaches. A total of 13,007 microplastics were counted, of which 99.6% were fibers. Most of them were transparent (38.34 %) and elongated (98.71 %). PedraBranca was the most contaminated beach, with 20,166.7 ± 13,392 particles m-3. Concerning depth, mean microplastic density was similar among the layers analyzed (0-20 cm =13,416.7 ± 5,070 particles m-3; 20-40 cm =10,510.0 ± 8,707 particles m-3, 40-60 cm=16,005.0 ± 16,011 particles m-3; 60-80 cm=9,566.7 ± 1,838 particles m-3, Kruskal-Wallis, χ2 = 1.34; p = 0.71) regardless of the beach. On PedraBranca, there were higher densities (33,316.7 particles m-3 ± 14,050) on the surface (0-20 cm), and on Flexeira beach, the density was higher (20,300.0 particles m-3 ± 15,230) in bottom layers (60-80 cm). On the other beaches, the highest densities occurred in the 40-60 cm layer, with 25,125.0 ± 21,460 particles m-3 on Vai-Quem-Quer beach, 18,400.0 ± 4,727 particles m-3 on Farol beach, and 9,816.7 ± 16,011particles m-3 on Fazendinha beach. These results show that Amazon river-estuarine beaches are exposed to microplastic contamination.