Microplastics pollution in the South American Pantanal

Microplastics represent an emerging global threat to freshwater ecosystems and studies in floodplains are still incipient. Microplastics in the Pantanal’s affluent and floodplains were sampled close to their potential urban sources and in the Pantanal lowlands. A 68 μm mesh size plankton net, with a 150 ml collection flask was used for sampling. The flask content was filtered over a 0.45μm Whatman paper, 47 mm in diameter, and examined under a stereomicroscope at 45X to identify and count microplastics (expressed as n100L -1 ). Microplastic sizes were determined by image microscopy. The average microplastic size was 192±142 μm and it was not significantly different in the urban tributaries (206±158 μm) than in the Pantanal (181±131 μm). The average±std microplastic concentration was 9.6±8.3, ranging from 1 to 31 n100L -1 . Fibers, fragments, pellets, and XPS (closed-cell extruded polystyrene foam) particles represented respectively 50%, 19%, 22% and 9% of the total microplastics. Microplastics concentrations were higher in the urban tributaries (19.9±5.8 n100L -1 ) than in the Pantanal lowlands (4.5±2.5 n100L -1 ). Fibers were always the most important fraction, followed by fragments. In the lowlands, pellets were scarce and XPS were absent. Comparison between microplastic composition in the floodplain and the urban areas suggest that pellets are transported from the urban area to the Pantanal, while microfibers and fragments could both be transported from the urban areas and have a local origin. These results indicate that microplastics are contaminating the Pantanal and its affluents and eventually can affect the local fauna. More research is needed to understand the extent and possible implications regarding the contamination by microplastics of the aquatic and terrestrial ecosystems of the Pantanal.