Seasonal Dynamics of Pathogenic Microorganisms (Cryptosporidium, Giardia and Fecal Bacteria) in an Artificial Lake Ecosystem (Sangsa Lake, Korea)

This study was performed for the purpose of monitoring monthly levels of two pathogenicmicroorganisms, Cryptosporidium and Giardia, from November 2005 to August 2007 in Sangsa Lake. Watertemperatures, pH and DO fluctuated seasonally at the study site. Annual mean values of BOD, COD and SSwere 0.8 mg L-1, 2.3 mg L-1 and 1.9 mg L-1, respectively. Although there was distinct seasonal variation in waterchemistry and chlorophyll a concentration, the lake generally contains low concentrations of nutrients andchlorophyll a. The relative abundance of coliform bacteria was always greater than that of fecal coliform. Thefecal coliform bacteria comprised 8.5～22.1% of total coliform bacteria. Seasonal analysis of Cryptosporidium andGiardia levels in the study site showed that in winter (November through February), Cryptosporidium oocysts andGiardia cysts were most abundant (1.1～1.8 × 10 cells L-1 and 3.8～5.1 × 10 cells L-1, respectively), while insummer (July through September) the abundance was lowest (0.0～0.3 × 10 cells L-1 and 0.9～2.9 × 10 cellsL-1, respectively). Molecular identification revealed two subtypes of Cyrptosporidium parvum in Sangsa Lake.