Towards a North Pacific Ocean Long-term Monitoring Program for Plastic Pollution: a Review of Global Occurrence of Microplastics in the Sea and Deep-sea Sediments

Abstract

Increasing production and inadequate management of plastic waste have resulted in the accumulation of plastic debris in the global biogeochemical cycles. In natural environments, these plastics become micronized by various physicochemical reactions, leading to the formation of microplastics. This review provides a concise literature account of the current state of MP contamination in sea sediments worldwide. We report on the capacity of the adopted sampling, pretreatment, and identification methods and provide recommendations for sustainable long-term deep-sea sediment monitoring programs. Our systematic review showed that for MP contamination in marine sediments, the number density of MPs with a minimum particle size of 0.1 mm ranges from 10 to 1, 000 items/kg-dry weight. On the other hand, the number density of MPs with a minimum particle size of 0.01 mm ranges from 100 to 10, 000 items/kg-dry weight. In all 31 papers analyzed, the percentage of fragments and fibers was over 50%. Polyethylene, used in containers and packaging, and polyester, a fiber used in clothing, were the most common polymer components. Analysis of sediment cores can reveal the history of MPs contamination. In addition, the deep-sea sediments have been identified as the endpoints of MPs that occur in the environment.