Plastic pollution in the aquatic ecosystem: An emerging threat and its mechanisms

The smaller fragments of plastics including microplastics and nanoplastics are of particular concern since their existence throughout the food web is more persistent than larger particles. 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 predator, including humans. These are detected in Asia, Europe and North America and the studies show 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 in the ingestion of large plastic material and/or particles. However, effects of ingestion of microplastic particles on marine organisms and the toxicity mechanisms are largely unknown. There is much more limited evidence of the impacts of microplastic intake on freshwater species, both in the limited number of studies performed and the number of species examined. However, the few recent studies of freshwater suggest that physical effects are analogous to those carried out in the sea. Therefore, we reviewed the state of the science for briefly identifying knowledge gaps and investigating research needs. To date, a small number of studies have been conducted to investigate biological effects of plastics on aquatic species, and the significant transport pathways of plastics from freshwater ecosystems to marine ecosystems and vice-versa have received little attention. So potential sources and the fate of the environment continue to be investigated. Likewise, there is limited research to explain how plastics and its fragments could transfer from the freshwater to terrestrial and to marine ecosystems, and to know if they can affect human health.