Bacterial species present in environmental water is highly influenced by salinity, temperature and pH. Resident bacteria in water may be carriers of antibiotic resistance genes (ARGs) located on mobile genetic elements. The aim of this study is to determine both microbial composition (microbiota) and ARGs in water samples collected from fresh water and marine sources as well as from areas with more or less human contamination. We will also compare environmental water microbiota with wastewater microbiota. The results generated will be used to estimate risk of transmission of antibiotic resistance in different water sources as well as to determine resident microbiota in sea, brackish sea water, and lake/river water in Sweden and in Europe.