Microplásticos em sedimentos superficiais da bacia do Espírito Santo e porção norte da bacia de Campos

Abstract

Millions of tons of plastic, including microplastic (< 5 mm), get into the ocean every year. Despite that, because of the lack of data, the knowledge about plastic waste distribution and dispersion in the sediments of the continental margins and the deep ocean remains still limited. The main objective of the present study was to verify the microplastic concentration (MPs) in different geomorphological environments (continental shelf, continental slope, continental rise, and submarine canyons) and relate them with depth or sedimentological parameters (granulometry, organic matter, and carbonates content). It quantified MPs in Espírito Santo’s basin and north Campos basin superficial sediments, in 71 samples distributed between 25 and 3.000 meters deep. The concentration varied from 0,06 to 1,24 (mean of 0,31 ± 0,20 debris) MPs per gram of sediment. The continental shelf (CS) showed about 34% of plastic debris, followed by the submarine canyons (27%), continental slope (21%), and continental rise (19%). Regarding the physical characteristics of the microplastic, fibers were the most common format (78%); black (31%) and blue (25%) were the most frequently found colors; and the dominant size was greater than 350 μm (typically between 500 and 200 μm), representing 56%. The concentrations of MPs were not significantly correlated with the sedimentological parameters. Furthermore, the plastic debris found in the PC was significantly different from the continental rise and continental slope. This study provides preliminary pieces of evidence that the MPs are accumulating in the deep ocean of the Brazilian continental margin, supporting the hypothesis that these environments are a major sink of MPs. While the MPs in the PC could have suffered influence, mostly, from the river and sewage discharge, the transport and deposition of MPs on deep-sea sediments may have been influenced mainly by vertical transport by sea snow. However, more studies are necessary, since the dynamics related to these depositions present impacts still unknown, but potentially harmful to the ecosystems of the deep ocean.