The relationship between Ascidians and plastic pollution: A systematic review of interaction mechanisms, biological impacts, and ecological roles

Microplastic (MP) and nanoplastic (NP) pollution are global threats that permeate marine ecosystems. As sessile filter-feeders, ascidians interact heavily with these pollutants. This systematic review synthesizes the literature regarding the interaction between ascidians and plastics, focusing on their role as bioindicators, physiological impacts, status as model organisms, and potential in vertical pollutant transport. Sixteen primary studies indicate that various ascidian species consistently accumulate MP, highlighting their strong potential as bioindicators. Significant sublethal impacts, including disturbances in reproduction, development, immune response, and oxidative stress, have been widely reported. Laboratory studies confirm that ascidians, particularly from the genera Ciona and Phallusia, are valid model organisms for tracking particle pathways, toxicity, and underlying molecular mechanisms. Moreover, evidence suggests that ascidians play a role in the vertical transport of MP from the water column to sediments through fecal pellets, underscoring their dual ecological function. In conclusion, ascidians are not merely passive victims but serve as a unique and multifaceted model system for plastic research. Further research is needed to standardize bio-monitoring protocols and validate their bioremediation potential in the field.