Silver nanoparticles alter plankton-mediated carbon cycle processes in freshwater mesocosms

Understanding the ecological impacts of nanoparticle exposure has become increasingly urgent, as these materials are now widespread in aquatic environments. However, the effects of nanoparticle exposure on plankton community-mediated carbon cycling remain poorly understood. This study investigated the effects of long-term (28-day) exposure to environmentally relevant concentrations (10 and 100 µg/L) of silver nanoparticles (AgNPs) on the plankton-mediated carbon cycling processes of freshwater ecosystems by constructing a mesocosm ecosystem. The results showed that AgNP exposure enhanced the photosynthetic activity and biomass of both phytoplankton and zooplankton, thereby promoting carbon fixation. AgNP exposure also increased the ecological niche breadth and carbon source utilization of planktonic microorganisms while disrupting lipid metabolism, which facilitated carbon decomposition and utilization. Furthermore, AgNPs promoted the transformation of organic carbon by reducing the content and chemical composition of dissolved organic carbon and increasing the sedimentation of particulate organic carbon in the plankton community. Notably, compared with the control, exposure to 10 and 100 µg/L AgNPs reduced CO₂ release at the water-air interface by 9 % and 17 %, respectively. Overall, this study provides the first evidence that long-term exposure to AgNPs can alter plankton-mediated carbon cycling processes in aquatic ecosystems, offering new insights into the ecotoxicological effects and risk assessment of nanoparticles.