Marine biodegradable polymers and zooplankton: A case study on the effects of PHBV microplastics on Artemia...

Polyhydroxybutyrate-co-valerate (PHBV) is a widely used copolymer from the polyhydroxyalkanoate family. Its biocompatibility and biodegradability make it a promising alternative to conventional plastics. However, the environmental impact of PHBV microplastics remains poorly understood. This study examines the physiological effects of primary PHBV microplastics on the zooplankton model Artemia franciscana, focusing on key endpoints such as survival, growth, feeding rate, developmental stage, gut histology, and lipid composition including fatty acid profiles, lipid storage and lipid peroxidation. Experiments involved short-term (24-48 h) and long-term (7-14 days) exposures to varying PHBV concentrations (10 to 500 mg·L^-1). PHBV biopolymer characterization through FTIR, laser diffraction techniques and SEM was done. Results indicated high survival across developmental stages, even when nauplii and juveniles were exposed to PHBV without food for up to 7 and 14 days, respectively. Notably, growth increased significantly at higher PHBV concentrations in presence of microalgae after 14 days. Long-term exposure at high PHBV concentrations altered the fatty acid profile with a concomitant decrease in lipid peroxidation. Also, it affected the cytoarchitecture of the digestive epithelium. Ingestion and egestion of PHBV microparticles were observed. SEM imaging revealed alterations in surface roughness between initial PHBV particles and those recovered from fecal pellets. These results involve distinctive physiological responses that may involve energy utilization from PHBV degradation and/or its action as a therapeutic agent. Overall, this research aims to enhance understanding of the ecological risks posed by biodegradable microplastics in aquatic ecosystems and their emerging role in global aquatic plastic pollution.