Factors driving the abundance and distribution of microplastics on sandy beaches in a Southwest Atlantic seaside resort

Microplastics are currently considered widespread marine pollutants, accumulating in sediments and shorelines around the world. Spatial distribution of microplastics in marine sediments is consequence of a combination of multiple factors (naturals and anthropics). We evaluated the drivers' factors of the abundance and distribution of two microplastics morphotypes (fibers and fragments) in surface sediments (5 cm deep) on SW Atlantic beaches with different plastics waste contribution along the coastline. Beach geomorphology, sediment grain size, distance to the urban area, continental waters discharge and human activities were the analyzed factors. Fibers abundance was significantly highest in pocket beaches, moderately exposed and closest to the urban center, while the fragments abundance was highest in beaches with stormwater outfall. The fine sand and the high recreational level were also factors driving the abundance of both morphotypes. Therefore, plastic morphotype and abundance vary according to the determining factors. [Display omitted] •First study of MP abundance in marine sediment from sandy beaches of Mar del Plata.•MPs were found in surface marine sediments of all sampled beaches.•Pluvials are the main source of microplastics fragments supply to the coast.•Beach morphology and distance to the center are drivers of plastic fiber abundance.•Fine sediments and high recreational activity contribute to MP pollution.