Assessment of marine debris on the Belgian Continental Shelf

•Marine debris was assessed in three marine compartments during two consecutive years.•Abundance and weight of both macrodebris and microplastic were assessed.•Plastics were the dominant type of macrodebris recorded: over 95% of recorded items.•Very high concentrations of beached macrodebris were observed.•In terms of weight, microplastics dominate the seafloor and sea surface.

A comprehensive assessment of marine litter in three environmental compartments of Belgian coastal waters was performed. Abundance, weight and composition of marine debris, including microplastics, was assessed by performing beach, sea surface and seafloor monitoring campaigns during two consecutive years. Plastic items were the dominant type of macrodebris recorded: over 95% of debris present in the three sampled marine compartments were plastic. In general, concentrations of macrodebris were quite high. Especially the number of beached debris reached very high levels: on average 6429 ± 6767 items per 100 m were recorded. Microplastic concentrations were determined to assess overall abundance in the different marine compartments of the Belgian Continental Shelf. In terms of weight, macrodebris still dominates the pollution of beaches, but in the water column and in the seafloor microplastics appear to be of higher importance: here, microplastic weight is approximately 100 times and 400 times higher, respectively, than macrodebris weight.