Microplastic occurrence and composition were investigated along the Polish coast (southern Baltic Sea) on 12 beaches differing in terms of intensity of their touristic exploitation, urbanisation and sediment characteristics. Their mean concentrations varied between 76 and 295 items per kg dry sediment. Fibres and plastic fragments were the dominant microplastic types. Overall, no relationship was found between their concentrations and sediment characteristics. Fine sediments were not identified as microplastic pollution traps. The highest microplastic concentrations were recorded at some urban beaches indicating that population density and the level of coastal infrastructure development are important factors affecting microplastic pollution level on beaches. On the other hand, microplastic concentrations in national parks did not differ substantially from the other beaches. Our results suggest that sediment accumulation processes may exceed microplastic accumulation, and overcome the effect of tourism and/or urbanisation, highlighting the role of the beach hydrodynamic status in structuring beach microplastic pollution.

The aim of the present study was to determine the effect of a long-term (113 days) exposure to microplastics on the development and induction of endocrine, geno- and cytotoxic responses in early life stages of sea trout Salmo trutta. Microplastic particles (3000 μm) of three most commonly mass-produced polymers (polystyrene - PS, polyethylene terephthalate - PET and polyethylene - PE) were applied in environmentally realistic concentrations (0.1% of sediment dry weight) in a laboratory experiment imitating the natural environment, typical for sea trout spawning grounds. The exposure of the sea trout, from fertilized eggs to mobile yolk-sac larvae, to microplastics did not affect the hatching success (the survival of embryos), hatching rate and the incubation period. Microplastics of any tested polymer type also had no adverse effect on the larvae survival, growth rate and the rate of yolk sack absorption. Similarly, no changes in frequencies of detected cytotoxicity endpoints compared to the control group were recorded. Exposure to polymer particles induced however the formation of genotoxicity endpoints (nuclear buds, micronuclei and blebbed nuclei cells). The level of total genotoxicity (ΣGentox) in fish larvae erythrocytes increased significantly in the following sequence: PS > PET > PE. No significant changes in the whole body corticosterone, dehydrocorticosterone and cortisone concentrations due to exposure to microplastics were recorded, while cortisol was detected in larvae exposed to PS. Our results show that long-term, non-ingestion related exposure to microplastics does not affect development of S. trutta early life stages but may lead to genotoxic responses. PS seems to be the most hazardous among all polymers studied. This is the first study demonstrating non-ingestion related toxicity of microplastics to the early life stages of fish.