The production and disposal of plastic products into the ocean increases every year. Several scientists study the effects of large plastic contaminants on marine ecosystems, but often neglect to research the damage caused by plastic nanoparticles. This study aims to reveal the impact of plastic nanoparticles on Daphnia Magna, and its survival, behavioral patterns, as well as brain structure. The Daphnia being used were kept in controlled aquaria environments with 3 Daphnias per aquaria. Plastic nanoparticles in sizes of 180nm and 53nm were then administered to select groups of Daphnias, and deaths were recorded on an hourly basis. The study determined that polystyrene particles were found within the brains of all fish who were fed with plastic nanoparticles. The brains of these same fishes also showed reduced water content, and even changes to the cerebral lobes to those exposed to 53 nm particles. One other health concern present in groups exposed to polystyrene particles is weight loss. Groups exposed to 53 nm particles were also more likely to swim longer distances to obtain food, making them more susceptible to predation. Fish that were given 180nm plastic particles varied from the 53nm group, in that they showed signs of hyperactivity. The results of this experiment imply that prolonged exposure to plastic nanoparticles do indeed have an effect on the biological structure of Daphnia Magna. The effects observed can hinder Daphnia Magna’s survival rate and alter the balance of predator and prey situations. It can also be implied that the effects of consumption of plastic contaminants are not limited to Daphnia Magna but also to those who consume them. Traces of polystyrene were found within all of the fishes exposed, meaning that those who consume these fish are also exposed the plastic nanoparticles. Further research would be necessary to study the effect of plastic nanoparticles on on other prey and food chain members.