Microbial water quality of the Georgian coastal zone of the Black Sea

► Most microbial quality indicators in the Black Sea coastal zone vary by season. ► Low salinity and high temperatures may encourage non-native bacteria in estuaries. ► Temperature greatly impacts the occurrence and abundance of native Vibrio species. ► Marine somatic coliphage abundance is proportional to fecal pollution indices. ► Microbial water quality in the Georgian Black Sea improved from 2000 to 2008.