Abstract
A study on bacterial abundance (acridine orange staining), activity (5-cyano-2, 3-ditolyl tetrazolium chloride staining) and viability (fluorescein diacetate staining) was conducted in Lake Timsah, Egypt from September to December 2010. Reduction in temperature (29 degrees C in September to 20 degrees C +/- 1 degrees C in December 2010) led to a 50% simultaneous reduction in counts of viable cells, 58% for active cells and relatively weak reduction (16%) in bacterial abundance. Bacterial abundances (2.8, 3 & 2 x 10(3) cell.ml(-1)) were higher than counts of active cells (1.1, 0.9 & 0.5 x 10(3) cell.ml(-1)) and viable cells (1.3, 1.2 & 0.65 x 10(3) cell.ml(-1)) for the three water depths 0.5, 3 & 7 m, respectively). Counts of the three bacterial groups were significantly different (p<0.05) at the three water depths studied. Abundances of viable and active bacteria in the three water depths studied correlated significantly where R(2) values were 0.996, 0.997 & 0.95 for 0.5, 3 & 7 m, respectively. Abundances of free living cells (2, 2 & 1.2 x 10(3) cell.ml(-1)) were higher than those of attached cells (0.6, 0.9 & 0.7 x 10(3) cell.ml(-1) while variable correlations were observed between abundance of attached cells (0.09, -0.6 & -0.2 x 10(3) cell.ml(-1) for CTC+ cells) and aggregates (0.5, 0.8 & 0.4 x 10(3) cell.ml(-1)) for same three water depths) which indicated adequate availability of nutrients in the lake during the period of study.