Ingestion of polyethylene microspheres occur only in presence of prey in the jellyfish Aurelia aurita.

Microplastic ingestion was studied in A. aurita, a bloom-forming, circumglobal medusa. Here, we determined whether factors such as the concentration of polyethylene microspheres (75-90 µm) or the absence/presence of prey affect the ingestion, duration of microspheres in the gastrovascular cavity (time of presence), and retention time. The presence of polyethylene microspheres' was determined by exposing medusae during 480 min to three different treatments (5000, 10,000, 20,000 particles L-1), and was checked every 10 min to ascertain whether they had incorporated any. Preliminary results show that microsphere ingestion occurred only in the presence of prey (⁓294 Artemia nauplii L-1). The time of presence of microbeads in A. aurita increased (103, 177, and 227 min), with increasing microplastic concentration, and the microbeads were egested within 150 min. This study initiates the understanding of the potential implications that arise of the encounter between jellyfish and microplastic agglomerates, and with perspectives for future research.

Capture, swallowing, and egestion of microplastics by a planktivorous juvenile fish.

Microplastics (<5 mm) have been found in many fish species, from most marine environments. However, the mechanisms underlying microplastic ingestion by fish are still unclear, although they are important to determine the pathway of microplastics along marine food webs. Here we conducted experiments in the laboratory to examine microplastic ingestion (capture and swallowing) and egestion by juveniles of the planktivorous palm ruff, Seriolella violacea (Centrolophidae). As expected, fish captured preferentially black microplastics, similar to food pellets, whereas microplastics of other colours (blue, translucent, and yellow) were mostly co-captured when floating close to food pellets. Microplastics captured without food were almost always spit out, and were only swallowed when they were mixed with food in the fish's mouth. Food probably produced a 'gustatory trap' that impeded the fish to discriminate and reject the microplastics. Most fish (93% of total) egested all the microplastics after 7 days, on average, and 49 days at most, substantially longer than food pellets (<2 days). No acute detrimental effects of microplastics on fish were observable, but potential sublethal effects of microplastics on the fish physiological and behavioural responses still need to be tested. This study highlights that visually-oriented planktivorous fish, many species of which are of commercial value and ecological importance within marine food webs, are susceptible to ingest microplastics resembling or floating close to their planktonic prey.