Uptake of Microplastics by a Tropical Freshwater Cladocera Revealed by Polyethylene Terephthalate Fluorescence

Inland waters potentially contain vast quantities of microplastics (MPs), being tropical ecosystems in developing countries possibly subjected to continuous and uncontrolled plastic waste disposal. This study reports on the intake of polyethylene terephthalate (PET) MPs by a small-sized tropical freshwater microcrustacean. We began by analyzing if the cladoceran Moina cf. micrura would ingest PET MPs with different shapes and sizes similar to the algae it feeds on (< 25 μm) but with lower concentration (9.4 × 102 particles/mL). We tracked the possible uptake of heterogeneous particles of PET MPs without dyes and nor fluorescently labeled by each individual during all the experiments via PET fluorescence under an epifluorescence microscope. Adults of M. cf. micrura and neonates born during the experiment ingested MPs, which accumulated (i) in the alimentary channels, (ii) on external parts of the cladocerans, (iii) on molting exudes, and (iv) in the gut and on appendages of dead individuals. We recorded efforts of MPs egestion by some individuals without success – which possibly contributed to the decrease in survival along the experiment. As Moina spp. are common tropical zooplankters and a widely recognized food source within aquaculture, the potential ecological consequences of such PET MPs ingestion on tropical aquatic food webs are highlighted.