First Assessment of Microplastics and Invertebrate Fauna in the Hyporheic Zone of the Large Paraná River (Argentina)

The goal of this study was to document the presence and density of microplastics and invertebrates in the hyporheic sediments of the large Paraná River in sandbanks (Argentina). Nine species of hyporheic invertebrates were recorded and identified for the first time, with an average density of 14,164 ± 13,889 ind./m³. Isotoma sp1 (12,729 ± 19,444 ind/m³) and Aelosoma sp1 (13,889 ± 24,056 ind/m³) were the most abundant species. The average concentration of microplastic was 25,000 ± 9,129 MPs/m³. All microplastics detected were polyethylene terephthalate (PET) fibers, with sizes ranging from 693 to 1,820 μm. While the absence of comprehensive QA/QC procedures constrains the precision of absolute concentration estimates, these findings provide important baseline information for the Paraná River, in which no previous data were available. The co-occurrence of invertebrates and microplastics in the hyporheic sediments of the Paraná River highlights the potential threat that microplastics pose to the survival of hyporheic invertebrates in river ecosystems.