Real-time assessment of the impacts of polystyrene and silver nanoparticles on hatching process and early-stage development of <i>Artemia</i> using a microfluidic platform

Abstract The development of real-time in-situ monitoring techniques is key to advancing a mechanistic understanding of the impacts of marine pollution, which is challenging to acquire through traditional end-point toxicity testing. We investigated the impacts of different nanopollutants on the hatching process and early-stage development of marine organisms, a vulnerable life stage, by observing oxygen consumption in real-time and morphological changes at regular intervals using a microfluidic platform. Here, two common and distinct nanoparticle (NP) types - polystyrene (PS) nanoplastic and silver (Ag) nanometal, were examined to assess and compare impacts on the hatching process and nauplius stage (first larval stage) of Artemia , a widely used zooplankton model in ecotoxicological studies. The study was conducted over a wide range of doses that are relevant to different environmental conditions, ranging from 0-1 mg/L, over a period of 24 hours. The hatching process of Artemia is comprised of four distinct stages which can be differentiated by metabolism and morphology: hydration, differentiation, emergence, and hatching. During hatching, NP exposure altered the time needed for the resumption of dormant Artemia cysts (hydration duration) at the lowest dose, dramatically prolonged the differentiation stage, and slowed embryo emergence from the cysts. The remaining time for the hatching stage during the experimental timeframe was also shortened. Overall, the presence of NPs led to increased oxygen consumption in multiple stages of the hatching process. Hatchability increased significantly with NP concentration although mortality showed an inverse pattern. This may be attributed to the increased aggregation of NPs in saltwater with increasing concentration which limits bioavailability during hatching but may be more readily consumed post-hatch. Ag NPs had a greater effect on hatching and mortality in comparison to PS NPs. A significant impact of NPs on swimming speed was observed, with a decrease observed in the presence of PS NPs and an increase observed in the presence of Ag NPs. Graphical abstract Highlights Utilization of oxygen sensor integrated microfluidic chip and microscopy for ecotoxicological study. Bioaccumulation of NPs affected hatching stages and respiration leading to inhibition of hatchability, with greater toxicity of silver NPs. NPs caused significant mortality and alteration in swimming performance.