Time-dependent effects of polystyrene nanoparticles in brine shrimp Artemia franciscana at physiological, biochemical and molecular levels.

Micro- (<5 mm) and nanoplastics (<1 μm) are emerging threats for marine ecosystems worldwide. Brine shrimp Artemia is recognized as a suitable model among planktonic species for studying the impact of polystyrene nanoparticles (PS NPs) through short and long-term bioassays. Our study aims to evaluate the time-dependent effects of cationic amino-modified PS-NH2 (50 nm) in A. franciscana after short- (48 h) and long-term exposure (14 days). For this purpose, nauplii were exposed to a concentration range of PS-NH2 (0.1, 1, 3 and 10 μg/mL) in natural sea water (NSW), and physiological, biochemical and molecular responses were investigated. Short-term exposure to PS-NH2 caused a decrease in nauplii growth and affected the development in a concentration-dependent manner, long-term exposure impaired the survival, but not the growth and feeding behavior. Oxidative stress was detected after short term exposure as the decrease in the activity of antioxidant enzymes, and was fully evident in the long-term as lipid peroxidation, suggesting an accumulative effect. The decrease in Cholinesterase (ChE) activity observed indicates possible neurotoxic action of PS-NH2. Also, Carboxylesterase (CbE) inhibition by PS-NH2, described for the first time in this study, anticipates potential effects in biotransformation of exogenous and endogenous compounds, being the crustacean juvenile hormone methyl farnesoate (MF) that regulates development and molting, one candidate. Furthermore, short- and long-term exposure to PS-NH2 affect the expression of genes involved in cell protection, development and molting. Overall, our results reveal that low PS-NH2 concentrations induce physiological, biochemical and molecular (changes in gene expression) alterations in Artemia, and point at their potential risk for this model organism, supporting the general concern about nanoplastics occurrences in aquatic environments and their ability to represent an ecological threat for aquatic zooplanktonic species.