The accumulation of plastic substances in the aquatic ecosystem is a threat that should not be underestimated. Smaller plastic pieces, such as microplastics and nanoplastics, are of particular concern since their presence in the food web is persistent. Microplastics enter in the food chain and its very bottom, when aquatic organisms eat or ingest contaminated food materials, and keep being transferred in the next food web such as predators including humans. It is evident that aquatic organisms frequently ingest microplastics across a variety of feeding guilds. Marine organisms may cause shock, inner or outer injuries, ulcerating sores, blocking digestive tracts, fake feelings, degraded feeding capabilities, fatigue, weakness, limited predator prevention, or death due to the ingestion of large plastic material and/or particles. However, effects of microplastic particles on marine organisms and the toxicity mechanisms are largely unknown. There is much more limited evidence of the impacts of microplastics intake on freshwater species, both in the limited number of studies performed and the number of species examined. However, a few recent freshwater investigations imply that the physical impacts are similar to those observed in the sea. As a result, we conducted a brief evaluation of the state of the science in order to identify knowledge gaps and research requirements to examine the impacts of microplastics on aquatic ecosystem. To yet, just a few researches have looked at the biological consequences of plastics on aquatic organisms, and the important transport pathways of plastics from freshwater to marine environments and vice-versa.