Microbial water quality in freshwater lakes with different land use

Aims The relationship between land use (undeveloped, cattle grazing, urban), faecal indicator bacteria (FIB) levels and microbial source tracking (MST) marker detection was investigated in lakes created following phosphate mining. Methods and Results Faecal coliforms and enterococci were cultured, and MST markers were detected by PCR [Methanobrevibacter smithii, human polyomaviruses (HPyVs), ruminant, human (HF183) and general Bacteroidales]. FIB levels varied significantly by sampling date and were correlated with antecedent rainfall. FIB levels varied with land use category only in the case of faecal coliform levels in sediments of urban lakes, which were significantly greater than those in undeveloped or cattle-impacted lakes. Ruminant Bacteroidales were detected consistently in cattle-impacted lakes (57%) and rarely in other lakes. HPyVs was the only human source marker detected. Conclusions Rainfall was more strongly associated with FIB levels than land use category. The detection frequency of only the ruminant MST marker was associated with land use. Significance and Impact of Study Microbial source tracking (MST) can fine-tune the assessment of human health risk from recreational use of inland waters, particularly when similar FIB levels but different surrounding land use and probable impacts exist.