Does Biofilm Promote Microplastics Palatability to the Aurelia sp. Ephyra Jellyfish?

Microplastics (MPs) are among the most significant pollutants worldwide. Due to their ubiquity and small size, MPs are mistakenly ingested by marine zooplankton, including cnidarians, representing a potential vector for toxicants and pathogens. Indeed, once in the ocean, MPs provide an ideal substrate for biofilm colonization, also termed “plastisphere”. The latter may alter the bioavailability and palatability of MPs, potentially inducing toxic effects. In this study, we investigated whether biofilm may promote MPs palatability in the juvenile stage (ephyra) of the jellyfish Aurelia sp. by exposing organisms both to fouled and not-fouled MPs for 24 h. To better mimic realistic environmental conditions, a mixture of stranded, in-field collected plastics was directly exposed to a marine environment to promote biofilm growth. Additionally, two ecotoxicological endpoints - immobility and behavioural alteration (pulsation frequency) - were assessed to evaluate the potential effects related to fouled and not-fouled MPs ingestion. Our results indicate that while biofilm does not enhance MPs palatability or induce significant ecotoxicological effects, it stimulates jellyfish pulsation at high MP concentrations (1 g/L). This response may be ascribed to the presence of colonizing phytoplanktonic organisms that may represent a food source and a nutritional value for ephyrae. These findings highlight the need for further investigation into the effects of biofilm formation and associated microorganisms on ephyrae, considering the trophic significance of jellyfish in marine food webs.