Assessment of the Microbiological Quality of Caspian Seawater and the Role of Physicochemical Factors on Microbial Load

Introduction: Analyzing the health risk associated with the microbial contamination of seawater is necessary to ensure that there is not any threat to human or environment. The aim of this study was to evaluate the microbiological quality of Caspian sea water using indicator bacteria. Some Physicochemical parameters were studied to assed their association with the contamination level of Caspian sea water due to the important role in the growth organisms in the seawater. Materials and Methods: In this study, 100 samples were collected from the northeastern zone of the Caspian sea, Iran, from November 2017 to December 2018. Total coliform, Fecal coliform, E.coli, Fecal Streptococcus and Clostridium perfringens were the indicator bacteria and temperature, pH, electrical conductivity, chloride and turbidity were water physicochemical factors according to standard methods. Results: The finding showed that the mean of Total coliform, Fecal coliform, E.coli, Fecal Streptococcus, and Clostridium perfringens were 614.72 ± 516.13, 62.11 ± 235.30, 49.69 ± 188.24, 348.02 ± 490.01 and 3.04 ± 5.76 MPN/100 ml, respectively. Furthermore, the mean and SD of temperature, pH, electrical conductivity, chloride, and turbidity were 13.84 oC ± 5.62, 8.27 ± 0.45, 17.96 ± 6.56 µs/cm, 5776.95 ± 1996.38 mg/l and 27.48 ± 15.82 NTU, respectively. Statistical analysis showed that microbial qualities were affected significantly by physicochemical factors, but the roles of water temperature were more than others. Conclusion: The microbiological results revealed that there was a remarkable level of contamination in some areas of Caspian sea. The results suggested that Clostridium perfringens provide better health risk prediction than other analyzed indicator bacteria, particularly in the warm season.