Environmental assessment of bacterial faecal pollution markers in overlying waters from an earthen fish pond

Anotace: This study was carried out to examine the sanitary quality of overlying waters in an earthen pond containing African catfish (Clarias gariepinus) in both wet and dry seasons. Water samples were collected twice weekly at different times of the day (i.e., morning and afternoon) from the earthen pond in Akure, Nigeria in August, September 2016, and February, March 2017 (n=48). Levels of faecal indicator bacteria were determined using membrane filtration method and physicochemical properties (such as temperature, pH, salinity etc.) of the overlying water samples were determined using standard methods. The results revealed that the concentration of E. coli in the overlying waters ranged from 0.78 to 1.40 Log10 CFU 100 ml-1 in morning samples and 0.85 to 1.38 Log10 CFU 100 ml-1 in afternoon samples while the concentration of faecal coliforms in the overlying waters ranged from 1.30 to 1.86 Log10 CFU 100 ml-1 in morning samples and 1.26 to 1.88 Log10 CFU 100 ml-1 in afternoon samples. Faecal coliforms showed the highest prevalence in both seasons compared to E. coli and intestinal enterococci and their levels were greater in the wet periods than the dry periods. The findings from this study suggest that the sources of faecal contamination of the overlying waters in the earthen pond originate mainly from non-human sources and the adoption of microbial source tracking techniques would further elucidate the appropriate management and mitigation strategies to control faecal contamination of the overlying waters in the earthen pond especially for human health protection.