Seasonal distributions of microplastics and estimation of the microplastic load ingested by wild caught fish in the East China Sea

Microplastic (MP) pollution in marine environments and organisms has received substantial international attention. However, long-term field studies of MPs are scarce. Here, we assessed the seasonal variation in MP abundance in the Zhoushan fishing ground (ZFG), one of the most abundant and productive fishing grounds worldwide, and analyzed the long-term MP accumulation in fish gastrointestinal tracts from September 2017 to June 2018. The most common MP particles in the ZFG were polyethylene terephthalate and polypropylene. After four seasons of continuous monitoring, we did not find accumulation of MPs in the fish after 10% KOH digestion. In total, 254 MP particles were removed from the gastrointestinal tracts of all fish. The average number of particles per fish was lower than that reported in previous global marine studies. There were significant differences among species. Moreover, this study provides the calculation of the weight of MPs ingested by fish and an estimate of the load of accumulated MPs in fish. According to the estimation, the load of MPs ingested by fish annually was approximately 3 kg in ZFG. These findings provide the long-term evidence of MP contamination in biota from the ZFG. The amounts of MPs ingested by fish require more detailed and improved investigation and estimation in further studies.