Major water-polluting microplastics (for example, polyethylene, polypropylene and others) have lower density than water. Therefore, they are concentrated in the neustonic layer near the water-air interface altogether with dissolved or colloidal natural organic matter, hydrophobic cells and spores of bacteria. This can cause environmental and public health problems because the floating micro- and nanoparticles of plastics could be coated with biofilm of hydrophobic and often putative pathogenic bacteria. Biofilm-coated microplastics are more attractive for consumption by aquatic animals than pure microplastics, and that increases the negative impacts of microplastics. So, impacts of even small quantities of microplastics in aquatic environments must be accounted for considering their accumulation in the micro-layer of water-air interphase and its interaction with bacterioneuston. Microorganisms attached to the surface of microplastic particles could interact with them, use them as substrates for growth, to change properties and biodegrade. The study of microbial life on the surface of microplastic particles is one of the key topics to understanding their role in the environment.