Realism in microplastics research? Learnings from multigenerational studies with Daphnia magna

, Schür Christoph, Wagner Martin.

The call for environmental realism in ecotoxicology studies with microplastics has largely been focused on moving away from spherical beads and emulating concentrations we are able to detect in the environment. But the interactions of microplastics and biota in the aquatic environment are shaped by a plethora of factors, both biotic and abiotic. We therefore expanded the standardized test protocols with Daphnia magna to include food limitation as additional stressor and to cover four consecutive generations of animals. The setup was used throughout two large-scale studies to compare effects of virgin and aged irregular microplastics as well as natural reference particles on Daphnia magna. Food limitation proved an effective secondary stressor, affecting all endpoints except mortality. Exposure to microplastics increased mortality and affected reproduction and growth endpoints, while the natural reference particles had no such effects. Exposure to aged microplastics produced lower mortality than virgin microplastics of the same batch but did not differently affect reproduction, adult and neonate size, and length development. The multigenerational approach under food limitation elicited insights otherwise not visible in shorter experimental periods, since most effects only manifested after several generations. We present the key learnings from both studies, compare our findings to those of similar studies, and translate them into recommendations towards future microplastics studies.

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