From macro to micro, from patchy to uniform: Analyzing plastic contamination along and across a sandy tide-less coast.

In search of an effective method to evaluate plastic contamination, macrolitter (>25 mm), mesolitter (5-25 mm), large microlitter (2-5 mm), large and small microplastics (2-5 mm and 0.5-2 mm) abundances in surface beach sands were simultaneously determined by two methods in four beach zones at six locations along the 100-km-long marine coast of the Curonian Spit National Park and the neighboring cities. Mean (median) content of plastic items per m is 0.85 (0.33) for macro-, 1.48 (0.40) for meso-, 3.35 (0.68) for large microlitter, and 3235 (1800) for microplastics (0.5-5 mm). The distribution of litter and microplastics (0.5-5 mm) is highly variable along and across the beach. The abundance of small-microplastics (0.5-2 mm) at the beach face is similar for all the locations and replicates. Swash-zone mixing, water percolation, importance of sediment pore size (rather than grain size), natural sorting of plastic particles at the beach face are considered.