Review on Microplastic Pollution in Marine Ecosystems: Sources, Distribution, Ecological Impacts, and Future Directions

Microplastic contamination is a significant global environmental issue affecting aquatic ecosystems. Due to their small size (< 5 mm), microplastics are readily ingested by marine organisms. Consequently, they enter the food web and transfer through trophic levels, ultimately leading to human consumption of microplastics, which may result in health concerns. This review synthesizes current knowledge on the sources, distribution, and impacts of microplastics in marine environments. Various sources contribute to the presence of microplastics, including the breakdown of large plastic waste, industrial activities, and everyday products. These tiny particles are found in all marine ecosystems, from the ocean’s surface to the seafloor. Many organisms can consume these microplastics, which may result in physical damage and introduce harmful substances into the food chain. The physical and chemical properties of microplastics play a crucial role in determining their environmental impact, with smaller particles being more likely to be ingested and potentially crossing biological barriers. Despite the growing body of research, several knowledge gaps remain, including the long-term ecological consequences, the effects of nano-plastics, trophic transfer, synergistic effects with other pollutants, and the need for standardized methodologies. Important findings from existing research highlight the widespread distribution of microplastics, their ingestion by marine biota, physical and chemical impacts, potential human health risks, sources, and sinks, impacts on biogeochemical cycles, interactions with climate change, ecological impacts, methodological advancements, and policy responses. This review aims to inform future research directions and support evidence-based policy decisions to address the growing challenge of microplastic pollution in marine ecosystems.