Tris(2-chloroethyl) phosphate alters gut microbiota and hepatic metabolism in freshwater turtles at environmentally...

Tris(2-chloroethyl) phosphate (TCEP), a widely used organophosphate flame retardant continuously released into freshwater ecosystems, poses potential environmental risks due to its persistence and mobility. While TCEP toxicity has been studied in aquatic organisms, its effects on reptiles remain understudied. This study exposed 40 juvenile male Mauremys reevesii to environmentally relevant TCEP concentrations (0, 10, 100, and 1000 μg/L) for 60 days. Although conventional toxicity indicators (growth, locomotor performance, digestive efficiency, liver condition) remained unaffected, TCEP induced significant molecular-level alterations exhibiting non-monotonic concentration-response patterns. 16S rRNA gene sequencing revealed concentration-related shifts in gut microbiota composition without altering overall diversity. Low-concentration exposure (10 μg/L) enriched beneficial Akkermansia correlating with increased food intake, while high concentrations (1000 μg/L) promoted potentially pathogenic taxa (Odoribacter, Bilophila, and Laribacter) and reduced feeding behavior. Hepatic metabolomic analysis identified 67 differential metabolites across treatment groups, with glycerophospholipid metabolism emerging as the primary disrupted pathway. Correlation analysis revealed significant associations between specific gut bacterial genera and hepatic phospholipid metabolites, indicating potential gut-liver axis involvement in TCEP-induced metabolic changes. This study provides the first evidence that environmentally relevant TCEP concentrations cause molecular effects in freshwater turtles through coordinated gut microbiota and hepatic metabolic responses, challenging traditional risk assessment approaches that may underestimate ecological impacts on long-lived reptilian species.