Temporal and spatial variations of pelagic microbial water quality in a coastal river-wetland area in a temperate climate zone

The introduction of anthropogenic pollutant loads into wetlands rapidly deteriorates water quality. This study was conducted in the Miliç River, a region with intense agricultural activities and coastal wetland characteristics. The Miliç wetland (fluvial wetland) is a receiving environment where the Terme Plain's drainage waters and the scattered settlements' waters are collected before they are poured into the Black Sea. In the study, monthly surface water samples were taken from four different sampling points of the Miliç River in the temperate climate zone, and total coliform, Escherichia coli, and Clostridium perfringens contamination from fecal indicators were investigated. Microbiological analyses were performed using standard methods with membrane filtration. The average colony count of the water samples at different stations in the Miliç River was determined as 2022 CFU/100 mL, 455 CFU/100 mL, and 34 CFU/100 mL for total coliform, E. coli, and C. perfringens, respectively. The highest fecal pollution was recorded during the rainy seasons (winter>autumn>spring>summer). In the correlation between stations and seasons, the highest correlation was determined for E. coli in winter (r= 0.985, p<0.05) and for C. perfringens in autumn (r=0.958, p<0.05). Analysis results show that there is fecal pollution in Miliç coastal wetlands. According to the bacteriological parameters in the Surface Water Quality Regulation, wetland water ranks II in total coliform bacteria count. The class is of water quality (slightly contaminated water). Regarding this parameter, the ecological status of the river-wetland is in the “good” water class. In terms of microbiological water quality, the Miliç River has values that are not very polluted but under the pressure of pollution. In order not to increase the level of fecal contamination, direct mixing of domestic waste/ wastewater, animal manures, industrial wastewater/rainwater channels, and drainage channels from settlements and agricultural areas in the wetland basin should be prevented, and the public should be made aware of the necessary precautions to be taken.