One-Year Monitoring of Microplastics in Mussels (Mytilus edulis) From an Industrialized Bay of South Korea

Abstract

Microplastics are prevalent in the marine environment, but little information is available about microplastic contamination from a longterm perspective. Long-term monitoring can reveal contamination trend and reflect environmental changes over time. The present study conducted a long-term monitoring using mussels (Mytils edulis) as a bioindicator to understand the monthly variations of microplastic contamination from an island in Masan Bay, South Korea. Mussel is suitable species for a long-term monitoring of microplastic contamination due to its abundance, widespread distribution and sessility which results in high accessibility. In addition, its capacity of filtering seawater leads to accumulation of microplastics. Mussels were collected monthly from February 2018 to January 2019. After a series of sample treatment process, all plastic-like particles were analyzed using micro-Fourier transform infrared microscope. The detection frequency of microplastics in mussels was 100%, confirming that microplastic contamination was widespread throughout the year. The annual mean concentration was 0.38 ± 0.16 n/g and 1.29 ± 0.61 n/individual. The microplastic concentration showed a decline trend from March to August, and increased through fall and winter. The monthly change of microplastics in mussel tissues was not large, but was slightly related to condition index of the mussels. Polyacrylate copolymer, polypropylene and polyethylene were found as dominant polymers, accounting for 21.4% to 72.2% of the total microplastics. The high abundance of polyacrylate copolymers could be due to frequent ship activities inside the bay as it is mainly used for ship paint resin. Fragments smaller than 300 μm were dominant (65-89%). The overall contamination characteristics of microplastic (shape, size, polymer type, and color) was consistent throughout the year. The results of this study provide information about monthly change in microplastic concentration in mussel, which would be useful in planning biomonitoring study of microplastics using bivalves.