Microplastics in the Marine Environment: Sources, Distribution, Biological Effects and Socio-Economic Impacts

Microplastic pollution is among the global environmental concerns of the 21st century due to its transboundary distribution and persistence in marine ecosystems. Increasing amounts have been recorded in the sedimentary cycle of marine environments, making microplastics potential indicators of the Anthropocene. However, efforts to mitigate plastic pollution are impaired by increasing annual production rates (> 340 million tonnes worldwide); by plastic material versatility, low cost and durability; by unregulated global trades; and by inefficient recycling and disposal practices worldwide. Preventing plastics and microplastics from entering the oceans must start with reducing plastic input at sources as well as improving waste management in a circular economy approach, as a long-term solution. The widespread distribution of microplastics in the marine environment has raised several questions over recent decades regarding their sources, amounts, toxicity, fate and effects on marine food webs and ecosystems. Recently, rivers and estuaries have been acknowledged as the main sources of microplastics from land to the open ocean. Due to their size, microplastics are ingested by organisms in the entire food chain; they are also potentially transferred along successive trophic levels and eventually can reach top predators. Microplastics can potentially transfer adsorbed and/or absorbed trace metals, organic pollutants, and additives throughout food webs, with unknown implic...