Combined effects of triclosan and nanoplastics on reproduction performance, population dynamics, and transcriptome regulation of rotifer (Brachionus plicatilis)

Since nanoplastics (NPs) possess the property of carrying aquatic pollutants, more studies have increasingly focused on their combined toxicity to aquatic organisms. In this study, the individual and combined effects of triclosan (TCS) concentration (0, 25, and 200 μg/L) and NPs size (none, 50, 100, and 500 nm) on the reproduction, population dynamics, biochemical responses, and transcriptomic profiles of rotifers were investigated. Results showed that high-dose TCS or 50 nm NPs significantly impaired the reproduction and population growth of rotifers, as evidenced by reduced offspring number, delayed the first breeding time, and decreased population density (p < 0.05). Notably, these detrimental effects were attenuated under the co-exposure of high-dose TCS and 50 nm NPs. Moreover, high-dose TCS and 50 nm NPs independently induced oxidative stress of rotifers (elevated levels of ROS and MDA, along with increased activities of SOD, CAT, and GST), while the oxidative stress was alleviated under the co-exposure of high-dose TCS and 50 nm NPs. Furthermore, transcriptomic analysis revealed that high-dose TCS significantly altered the expression of key genes involved in fat and carbohydrate digestion and absorption pathways, while 50 nm NPs primarily affected genes related to adherens and tight junction pathways. Importantly, under the co-exposure of high-dose TCS and 50 nm NPs, the fat digestion and absorption pathway in rotifers remained unaffected, and the effects on carbohydrate digestion and absorption, as well as adherens and tight junction pathways, were attenuated. In conclusion, the co-exposure to TCS and NPs exhibited an antagonistic interaction, attenuating the toxic effects on rotifers compared with single TCS or NPs exposure.