TABLE 4.

Protozoan parasites in surface waters in Amsterdam

Sitea	Type of quantity	Cryptosporidium			Giardia
		No. of positive samples/total samples	Total count (no. of oocysts/ 10 liters)	Viable count (no. of oocysts/ 10 liters)	No. of positive samples/total samples	Total count (no. of cysts/10 liters)	Viable count (no. of cysts/10 liters)
Nonrecreational sites
IJmeer		2/8			7/8
	Mean		0.4	0.2		35	30
	Median		0	0		34	16
	Range		0-2	0-1		0-105	0-84
Amstel		5/8			8/8
	Mean		2.4	1.2		68	53
	Median		1	0		60	44
	Range		0-9	0-5		8-157	7.2-157
Herengracht		5/8			8/8
	Mean		2.2	1		45	37
	Median		1	0		27	48
	Range		0-10	0-7		1-118	0-94
Prinsengracht		6/8			8/8
	Mean		5.7	4.4		70	55
	Median		2.6	0.5		69	55
	Range		0-29	0-29		2-167	2-134
Recreational sites
Amsterdamse Bos		4/11			0/11
	Mean		0.5	0		0	0
	Median		0	0		0	0
	Range		0-2	0		0	0
Gaasperplas		2/11			3/11
	Mean		0.6	0.6		0.4	0
	Median		0	0		0	0
	Range		0-4	0-4		0-2	0
Nieuwe Diep		1/11			6/11
	Mean		0.1	0		2.5	1.2
	Median		0	0		1	0
	Range		0-1	0		0-11	0-5
Sloterplas		5/11			6/11
	Mean		1.4	0.3		1.1	0.3
	Median		0	0		1	0
	Range		0-12	0-1		0-4	0-4
Nieuwe Meer		2/11			5/11
	Mean		0.3	0.2		2.2	1.2
	Median		0	0		0	0
	Range		0-2	0-1		0-8	0-8

^aNonrecreational sites were sampled eight times from June 2003 to June 2004; recreational sites were sampled 11 times from September 2004 to September 2005.