Ecotoxicological Impacts of Micro and Nanoplastics on Marine Fauna

Mismanagement of plastics has resulted in increasing plastic wastes in the environment, particularly the marine environment acting as the ultimate sink of plastics disposed into waters and even onto land. Micro- and nanoplastics in the marine environment undergo aggregation, sedimentation, deposition and enter the food chains as they are ingested by marine fauna. The uptake of micro- and nanoplastics by marine fauna poses multiple ecotoxicological effects comprising the blockage of alimentary canal and gills, behavioral change, physiological interference especially of the endocrine, antioxidative, immunity and hepatic systems, as well as adverse effects on reproduction and development of marine fauna. The ecotoxicological effects are often complicated by the ability of the micro- and nanoplastics to adsorb a wide range of chemicals. Nanoplastics have been found to affect cellular functions and membrane integrity and are able to cross the blood-brain barrier of certain aquatic species. The effects vary with the types of plastics, species of marine fauna, the dose as well as the sizes of plastics. This review systematically and concisely presents the toxicological effects of micro- and nanoplastics on marine fauna and highlights the need to understand the effects of these plastics at environmental concentrations instead of experimental concentrations. It also calls for the study of ecotoxicological effects of micro- and nanoplastics to be extended to more plastics types and sizes as well as more marine species.