Trophic-transferred hierarchical fragmentation of microplastics inducing distinct bio-adaptations via a microalgae-mussel-crab food chain

Microplastics (MPs) are alarming social issues owing to their detrimental influences on both ecology and human health. Although MPs retained in low-trophic organisms are assumed to be transferred to high-trophic organisms via the food chain, concrete knowledge about the physical-chemical alterations of MPs via trophic transfer and the impact of trophic-transferred MPs on organisms remains scarce. Here, we established a three-tiered (microalgae-mussel-crab) trophic-transfer model to systematically investigate the bio-accumulation and distribution of polyethylene MPs (PE-MPs, 10-45 μm), and subsequent induction of antioxidant defenses in marine organisms with pivotal ecological and economic status at each trophic level. Results demonstrated that microalgae's growth and quality as feeds were hampered due to attachment to PE-MPs, whose physical-chemical properties were hence altered. This affected the intake and occurrence of PE-MPs in mussels, where PE-MPs were initially fragmentized. Following mussel-crab transfer, further fragmented PE-MPs in crabs resulted in stronger internalization and active internal transport among tissues. Despite successful antioxidation observed in both consumers, severer stress was posed on tissues in charge of metabolism and detoxification, leading to serious DNA damage. Overall, hierarchical fragmentation can increase internalization and bio-transportation of MPs via trophic transfer leading to longer retention and stronger capacity across biological barriers, which is speculated to pose further risks to higher-trophic organisms (e.g., humans).