The occurrence, fate, and effects of microplastics in the marine environment

The annual global plastic production was estimated to be 322 million tonnes worldwide in 2015. Most plastic, including microplastic that enters the sea, originates from land-based sources, such as sewage and storm water, or ocean-based sources, including discarded and lost fishing items. Microplastics have been defined as plastic particles with size < 5 mm in diameter, which can be divided into primary microplastics and secondary microplastics. Primary microplastics are most commonly found in industrial, domestic cleaning products and synthetic textiles, while secondary microplastics are usually fragmented from larger plastic debris via weathering, ultraviolet degradation, or biodegradation. Microplastics have been found in the open-sea sediments, deep-sea sediments, and beach sediments worldwide. Microplastics have been found in Europe, Asia, America, India, and even polar regions, and East Asia has been identified as a potential hot spot. Due to their biodegradation-resistant properties, microplastics can persist and accumulate in the marine environment. Thus, it can cause physical and chemical effects on various marine organisms after ingestion. Microplastics can be a vector for the absorption of hydrophobic organic pollutants and heavy metals and potentially transfer of these compounds through the food web. This review summarizes and provides updated data on the sources and occurrence of microplastics in the marine environment, as well as the fate and effects on marine organisms. Finally, recommendations such as legislation reinforcement, raising awareness through education, and a microplastic remediation approach by applying microbes were suggested to control the sources of plastic entering the marine environment. Copyright © 2018 Elsevier Inc. All rights reserved.