TABLE 2.

Cell counts of cyanobacteria and microcystin concentrations in natural samples from lakes which were used for isolation of Microcystis colonies

Lake	Sampling date	Source	No. of cells (cells/liter) ofa:			Toxin concn
			Microcystis sp.	Anabaena sp.	Aphanizomenon sp.	Microcystin concn (μg/liter)	Amt of microcystin per Microcystis cell (fg/cell)
‘t Joppe	27 June	Water column	8.1 × 103	2.4 × 104	4.5 × 102	0.22 (0.18)	27
	29 August	Water column	5.5 × 104	5.3 × 102	0	2.64 (0.03)	48
		Scum	5.6 × 106	ND	ND	420 (22.9)	75
	28 September	Water column	7.8 × 104	1.4 × 103	88	0	0
		Scum	6.1 × 107	ND	ND	3,308 (244)	55
Zeegerplas	20 June	Water column	5.4 × 104	1.8 × 105	0	0	0
	20 August	Water column	2.8 × 105	1.0 × 105	0	0.60 (0.09)	2

^aND, not detected.