Microplastics have been detected in all marine regions and habitats, from the poles to the deep seas. A number of marine species are known to ingest microplastics, resulting in detrimental impacts. Preliminary work carried out on sea squirts suggested that microplastics may have a negative impact upon their health. Here, the solitary sea squirt, Ciona intestinalis, is used as a model species to observe the impacts of microplastics on sea squirts. This species has a transparent body form and is widely available in coastal waters. Laboratory exposures were carried out using a range of different microplastics; fluorescently labelled polystyrene (PS) and polyamide (PA) microbeads, polyhydroxybutyrate (PHB), low density polyethylene (LPE), polypropylene (PP), nylon fibres (NF), nylon particles (NMP) and polystyrene nanoparticles (PNP), cryo-ground polypropelyne rope fibres, rubber loom bands, high density polyethelyne (HDPE) and polyvinyl chloride (PVC). C. intestinalis ingested all but the cryo-ground rope fibres. Buoyancy is likely to have been an important factor for ingestion by C. intestinalis. Polystyrene and polyamide microbeads were ingested at all concentrations tested (100 and 500 PS beads mL-1, 500 and 1000 PA beads ml-1). However, there were significantly more PS beads in C. intestinalis at 24 hours than at 72 hours. Microplastic egestion was also observed, following ingestion plastics were found to be present in faecal matter. There was no distinct pattern of bead content within the sea squirts or surrounding water with time after removal from plastic contaminated water. C. intestinalis readily ingested microplastics of the tested size ranges, but were able to rapidly eject them without obvious detrimental effects. Wild specimens of C. intestinalis were also analysed for the presence of microplastics. A number of plastic-like particles were found to be present within these organisms, suggesting that ascidians may be susceptible to microplastic ingestion in the marine environment
