Investigation of Microplastics in Surface Water and Estuarine Mullet Mugil cephalus from 23 Estuary Areas, South China

Microplastics, which are defined as small plastic particles smaller than 5 mm, have been found in various aquatic environments all over the world. In this study, we investigated the level of microplastics in the surface water and estuarine mullet Mugil cephalus from 23 estuary areas in the south of China. M. cephalus, due to its wide distribution and high tolerance, was selected as a candidate fish species for monitoring the ingestion of marine microplastics. The size, color, and type of all microplastics were recorded from the water and fish samples by stereomicroscope. The average abundance of microplastics was 18,261 items/m3 in the surface water, and 7.2 items/individual in fish. These alarming numbers revealed significant pollution due to microplastics in the environment. Fragments and minute-sized particles were the most common features found in both the water and the fish samples. Some impurities in the water sample were easily confused with microplastics, but regular forms on the surface of the impurity could be distinguished by using scanning electron microscopy (SEM). The shape, color, and size of the microplastics in the fish and water samples were similar, which suggested that the microplastics in the water might enter the organisms’ body, thereby affecting the health of aquatic species and even humans. Based on these findings, it is highly recommended that the monitoring and managing of pollution due to microplastics be addressed in the estuaries.