TABLE 2.
Physical and chemical characteristics, numbers of cyanobacterial cells, and microcystin concentrations in Lake Mikata
| Sampling date | Temp (°C) | NO3-N concn (mg liter−1) | PO4-P concn (mg liter−1) | No. (%) of cells (cells ml−1) ofa:
|
Total cyanobacterium concn (cells ml−1)b | Microcystin concn (ng liter−1) | ||
|---|---|---|---|---|---|---|---|---|
| M. aeruginosa | Anabaena sp. | Planktothrix sp. | ||||||
| 13 April | 13.1 | 0.3636 | 0.0078 | 1.6 × 101 (0.3) | ND | 5.2 × 103 (99) | 5.2 × 103 | 0.15 |
| 9 May | 19.7 | 0.0032 | 0.0021 | 2.7 × 102 (0.4) | ND | 6.3 × 104 (99) | 6.3 × 104 | 3.25 |
| 6 June | 24.3 | 0.0016 | 0.0022 | 2.2 × 102 (0.05) | 2.7 × 105 (56) | 2.1 × 105 (43) | 4.8 × 105 | 1.34 |
| 4 July | 26.1 | 0.0025 | 0.0031 | 2.4 × 102 (0.07) | 1.5 × 105 (42) | 2.0 × 105 (57) | 3.5 × 105 | 0.75 |
| 1 August | 27.9 | 0.0507 | 0.0029 | 3.7 × 102 (0.2) | 2.1 × 104 (8) | 2.3 × 105 (91) | 2.5 × 105 | 3.34 |
| 5 September | 27.3 | 0.0020 | 0.0019 | 6.3 × 103 (2) | 2.6 × 105 (65) | 1.3 × 105 (33) | 4.0 × 105 | 5.03 |
| 3 October | 23.7 | 0.0232 | 0.0017 | 6.6 × 102 (1) | 4.7 × 102 (0.7) | 6.2 × 104 (98) | 6.3 × 104 | 1.86 |
| 8 November | 16.0 | 0.0030 | 0.0012 | 3.2 × 101 (0.3) | 1.0 × 104 (99) | ND | 1.0 × 104 | 0.44 |
| 4 December | 9.9 | 0.1602 | 0.0052 | ND | ND | 4.7 × 104 (100) | 4.7 × 104 | ND |
a
Percentages were determined as follows: number of cells of taxon/total number of cyanobacterial cells detected by microscopy × 100. ND, not detected.
b
The total cyanobacterium concentration is the sum of the M. aeruginosa, Anabaena, and Planktothrix concentrations.