The Paradoxical Toxicity of Microplastics under Predation Risk: The Driving Role of Gut Microbiota-Mediated Tolerance

genotypes revealed that the fish-adapted clone exhibited superior tolerance to combined exposure to stressors, maintaining robust growth and defensive integrity, unlike the fish-naïve clone. The gut microbiome was identified as a key mechanistic driver. The fish-adapted clone maintained a more stable microbial community structure with functions enriched in carbohydrate metabolism and immune defense. A reciprocal transplantation experiment provided causal evidence: transplanting the adapted microbiota into the predator-naïve clone reduced mortality by 39% and increased intrinsic growth by 22% under combined stress. These findings highlight that microplastics risk assessment may be flawed if they ignore the eco-evolutionary context of natural stressors.