Limited ingestion, rapid egestion and no detectable impacts of microbeads on the moon jellyfish, Aurelia aurita.

Jellyfish are voracious planktonic predators that may be susceptible to ingesting microplastics. We measured rates of ingestion and egestion of microbeads by Aurelia aurita (Scyphozoa) and evaluated whether ingesting microbeads affected metabolism or gut epithelia. Ingestion rates were measured by exposing medusae to microbeads and randomly sampling them 6 times over a 32 h period to determine the number of microbeads in their tissues. Egestion rates were measured by exposing medusae to microbeads for 1 h before transferring them to kreisels without microbeads and sampling them 6 times over 8 h. Respiration rates of medusae were determined using incubations and potential damage to gut epithelia was evaluated using histopathology. Medusae ingested few microbeads and egested them within 8 h. Microbeads had no effect on respiration and the histology. We concluded that the medusae may recognise microbeads as non-food particles and that their ingestion caused undetectable physiological and histological harm.