Behind the scenes: Who is the polluter of Slovenian coast

Plastic litter in the marine environment is receiving increasing attention. Namely, through rivers, ship traffic and recreation is anthropogenically produced litter introduced into the marine environment. Sun radiation and mechanical impact degrade plastic items into smaller pieces, i.e. secondary microplastic. Alternatively, primary microplastics from cosmetic products can enter the environment through waste water drains. The number of microplastics at beaches can vary substantially. In this study, the occurrence and the quantity of the microplastic in the Slovenian beach sediments was investigated. Samples were taken in March 2017. Microplastic particles were isolated by density separation in an aqueous solution of common salt (NaCl). The floating particles were separated and filtered over a 100-µm metal filter. Assumed microplastics were photographed and their characteristics were noted (i.e. source, form, color) and stored in glass vials with a Teflon lid. Potential contamination during the processing of the samples was controlled with a white filter in petri dish exposed to air. The reliability of the separation method was confirmed by a recovery experiment which yielded 86-90% recovery of intentionally added microplastic. Secondary microplastic were present as fragments, films, and fibers. However, the present study showed lower concentrations of microplastic at the Slovenian beaches than previously reported by Laglbauer et al. (2014, Marine Pollution Bulletin 89: 356-366). The differences in the concentrations are probably due to seasonal fluctuations of microplastic concentration. Moreover, contamination was not considered in the former study. Potential pollutants of the Slovenian coast are tourism, industry, sea- and road traffic, wastewater treatment plant, port, and agriculture. Since Laglbauer et al. (2014) excluded tourism as the contributor of the microplastic pollution the real contributors need to be identified. Polluted beaches are not attractive and may scare tourists and, thus, impair economy.