Temperature and polystyrene nano- and microplastics co-exposure alters physiology and metabolome in the invasive snail Pomacea canaliculata.

Microplastics and degraded nanoplastics are widespread freshwater pollutants that pose the ecological risks to aquatic organisms, while temperature variation can modulate their environmental fate and toxicity. Therefore, understanding the combined effects of temperature variation and nano- and microplastics on Pomacea canaliculata is crucial for ecological risk assessment. In this study, P. canaliculata was exposed to 5 μm polystyrene microplastics and 20 nm polystyrene nanoplastics at 15, 25, and 35 °C for 14 days. Physiological responses were determined via an assessment of key enzyme activities (antioxidant, immune-related, and digestive) and non-targeted metabolomic profiles in the hepatopancreas. Exposure to polystyrene nano- and microplastics under varying thermal conditions altered physiological and metabolic responses in the hepatopancreas of P. canaliculata. Combined exposure significantly affected catalase, superoxide dismutase, and lipase activities, whereas acid phosphatase, alkaline phosphatase, and amylase were mainly regulated by temperature. Responses were more pronounced under high temperature, with the 35 °C plus 20 nm nanoplastics treatment showing the greatest metabolomic alterations. Size-dependent differences were also evident: 20 nm nanoplastics, particularly at 35 °C, induced higher antioxidant enzyme activities than 5 μm microplastics and were more closely associated with redox regulation, transmembrane transport, and damage clearance, whereas 5 μm microplastics were more closely related to membrane lipid metabolism and lipid-mediated signaling. These findings indicate that temperature, particularly high temperature, can reshape the toxic effects of polystyrene nano- and microplastics in P. canaliculata, highlighting the need to incorporate both thermal background and particle size into ecological risk assessment.