Effects of microplastics on the foraging activity of a Neotropical shredder

Microplastics may negatively affect shredder invertebrates in aquatic ecosystems, influencing litter breakdown and nutrient cycling, resulting in adverse effects on the trophic chain. Phylloicus Müller, 1880 (Trichoptera: Calamoceratidae) serves as a model shredder invertebrate due to its relevant role in leaf processing and high biomass. Our objective was to investigate how microplastics at different concentrations affect the survival, biomass gain, case-building, and organic matter consumption by Phylloicus (caddisfly). Leaf consumption by Phylloicus was assessed in microcosms (14 × 9 cm) with treatments of high (0.2 g/l) and extreme (1 g/l) microplastic concentrations, as well as a control. Per capita leaf consumption averaged 4.54%, with lower values in the control and high concentration treatments compared to the extreme concentration. Case-building by Phylloicus did not vary significantly among treatments, with a per capita average of 4.45%. Similarly, the intraocular distance of Phylloicus, considered a proxy for biomass, showed no significant variation, averaging 0.015 mm. No significant differences in survival were observed, with an average survival rate of 66.7%. Our results suggest that there was no influence of microplastic exposure on Phylloicus mortality, growth, or case-building, even at extreme concentrations. However, the observed increase in consumption may affect caddisfly-mediated ecosystem processes, such as nutrient cycling.