Microplastics pollution in the South American Pantanal

Microplastics represent an emerging global threat to freshwater ecosystems. Studies regarding their presence 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 plankton net (68 ​μm mesh size), with a 150 ​ml collection flask was used for sampling. The flask content was filtered over a 0.45 ​μm Whatman paper, 47 ​mm in diameter, and examined under a stereomicroscope at 45X to identify and count microplastics (expressed as x100 ​L−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 x100 ​L−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 x100 ​L−1) than in the Pantanal lowlands (4.5 ​± ​2.5 x100 ​L−1). Fibers were the most important fraction, followed by fragments. In the lowlands, pellets were scarce and XPS were absent. A comparison between microplastic composition in the floodplain and the urban areas suggest that microfibers and fragments could be either transported from the urban areas or have a local origin. These results indicate that the biota of the Pantanal and its affluents is exposed to microplastics. More research is needed to understand the extent of the microplastic pollution and the risks posed by this contamination in the aquatic and terrestrial ecosystems of the Pantanal.