Costa, José Lino Vieira de Oliveira, 1964-Torres, PauloAmorim, Luísa Madalena Mendes2023-10-182023-10-1820232023http://hdl.handle.net/10451/59892Tese de mestrado, Ecologia e Gestão Ambiental, 2023, Universidade de Lisboa, Faculdade de CiênciasEvery year, millions of tons of solid waste are thrown into the sea with negative implications for the environment and, consequently, for the ecosystems and species that inhabit it. Commercial maritime traffic and ocean gyres lead to a significant increase in the amount of pollution in the waters and coasts of remote oceanic islands. Most of this type of pollution is plastics items, and those that are smaller than 5 mm are considered microplastics. These particles are ubiquitous throughout the marine environment, dispersed among beaches, estuaries, on the water surface and even on the seafloor, affecting ecosystems and impairing species. The objective of this study was to estimate the abundance and dimension of microplastics along the coast of São Miguel Island, Azores, following an inshoreoffshore gradient along a stream until the ocean. Sediment samples were collected and analysed for across 8 areas covering the entire coastline of the island, each one divided among 4 connected sites, along an inland-coastal gradient, from the stream until the ocean (upstream, downstream, coastal, and submerged marine sediments), following a nested design approach. Also, apart from this first approach, 15 beaches, covering all island, were also tested and compared. In both sampling approaches (areas and beaches), the highest abundance of microplastics was 0.74 MP/g (Ribeira Quente), and the lowest 0.20 MP/g (Ribeira Praia), both in South beaches. The largest category of microplastics was fibres, followed by microbeads and fragments, and the most abundant colours were transparent, black, and blue. There was significant variability in the abundance among areas, sites and beaches, and only among sites and beaches in the dimension. Factors like granulometry, sites and pollution sources are detected as significant in microplastics abundance. This study results are important to the scientific community and particularly for local government concerning litter management and mitigation.engPlásticolixo marinhosedimentozona costeirailhas oceânicasTeses de mestrado - 2023master thesis203490460