Microplastic concentrations in beach sediments along the German Baltic coast

• Microplastic concentrations were monitored at beaches along the German Baltic coast.
• Microplastics are distinguished from natural sediment based on intense colouring.
• Contaminations of at least 0–7 particles/kg and 2–11 fibres/kg sediment are found.
• Harbour, industrial, touristic activity are identified as likely sources.
• Natural sand grains are suspended by surface tension after density separation.

The contamination with microplastic particles and fibres was evaluated on beaches along the German Baltic coast. Sediments were sampled near the Warnow and Oder/Peene estuaries, on Rügen island and along the Rostock coast to derive possible entry pathways. Seasonal variations were monitored along the Rostock coast from March to July 2014. After density separation in saline solution, floating particles were found to be dominated by sand grains. Water surface tension is shown to be sufficient to explain floatation of grains with sizes less than 1.5 mm. Selecting intensely coloured particles and fibres, we find lower limits of the microplastic concentrations of 0–7 particles/kg and 2–11 fibres/kg dry sediment. The largest microplastic contaminations are measured at the Peene outlet into the Baltic Sea and in the North Sea Jade Bay. City discharges, industrial production sites, fishing activity and tourism are the most likely sources for the highest microplastic concentrations.

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