Microplastics in the World Oceans and Strategies for Their Control

Marine ecosystems are the final sinks for plastic debris and microplastics (MPs) arising from inland sources. Despite the findings from research studies, the overall MPs in all oceans are not completely illustrated. This review summarizes MPs' data (2015-2023) from 2068 locations in all five oceans, including bays/gulfs, seas, mid-oceans, and 202 marine fish species. Varying concentrations were recorded in the surface waters and mainly the gastrointestinal tract of the fishes, with sizes mostly from 0.1 to 5 mm. Polyethylene (PE; 30.3%), polypropylene (PP; 18.7%), and PE terephthalate (PET; 11.8%) were the major polymers, whereas fragments (41%) and fibers (38%) were the dominant shapes in water. Fishes were mainly documented with PE (36%), PP (17.6%), and polyamide (PA; 8%), which were in the form of fibers (55.5%) and fragments (30%). These MPs are considered to be a threat to the biota and must be controlled at the source. Strategies such as wetlands to reduce the flow of storm waters, the addition of clumping agents/algae in wastewater treatment plants to trap MPs, and the replacement of plastic goods with biodegradable or sustainable products are discussed in this review that can significantly reduce the accumulation of inland MPs in the seawaters. Relatively, challenges in the path of plastic waste and MPs' management are analyzed to direct future research and policies. This review may help illustrate their migratory and distribution patterns from the coastal areas to the mid-ocean. It will further provide a consistent data set for marine plastic waste management.