Microplastics in Harbour Seawaters: A Case Study in the Port of Gdynia, Baltic Sea

An important source of microplastics (MPs) in the Baltic Sea waters is plastic waste, which is fragmented in the natural environment. The pilot research on the identification of microplastics in the surface waters of the Port of Gdynia is presented. In this paper, microplastics of particle sizes 0.3–5 mm in harbour seawaters were investigated. Microplastics were collected from five harbour basins using an unmanned mobile research unit, HydroDron-1. Sampling of microplastics on the surface port water was conducted over four seasons. The collected plastic particles were separated by chemical oxidation and flotation in the NaCl solution (density 1.2 g/cm 3 ). Polymer identification was carried out by visual and microscopic observations, as well as using the Total Reflection Fourier Transform Infrared spectroscopy. Based on tows conducted in five basins of the Port of Gdynia, in total, the concentration of microplastics identified ranged from 0.082 mg/m 3 to 0.524 mg/m 3 , depending on the investigated basin. Four groups of microplastic shapes (fragments, films, fibres and spheres) were detected in all the investigated harbour basins. Fragments and fibres were prevalent when categorised by particle shape, whereas when categorised by colour, transparent, white and black particles were dominant. The predominant type of the identified polymers was polyolefins (PE, PP, PS) and their derivatives.