Time- and Temperature-Dependent Effects of PHBV on Physiological Responses in Brine Shrimp

Aquatic organisms are exposed to multiple stressors, including microplastic pollution and rising temperatures. Bioplastics like Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) are considered sustainable alternatives to conventional plastics, although their biological effects remain poorly understood. This study evaluated the effects of PHBV microplastics on Artemia franciscana under different temperature and exposure conditions. Organisms were exposed to 25 and 100 mg·L^-1 PHBV for 7, 14, and 21 days at 25 °C and for 14 days at 29 °C. Growth, development, antioxidant enzyme (CAT, GST) and esterase activities (ChE, CbE), lipid peroxidation (LPO), gut histology, fatty acid profiles and polymer particle length distributions were assessed. Growth and development increased with PHBV concentration, exposure time, and temperature. Enzymatic activities and LPO were significantly affected by these factors, although no evidence of oxidative damage was detected. Marked gut lesions were observed at 100 mg·L^-1 PHBV at 29 °C after 14 days. Fatty acid profiles were mainly influenced by time and temperature, while high PHBV levels were associated with additional, more subtle changes in long-chain polyunsaturated fatty acids. PHBV particle length distributions also varied depending on exposure conditions. These findings suggest that PHBV induces physiological responses distinct from those typically reported for conventional microplastics and highlight the importance of considering multiple stressors in ecotoxicological studies.