TABLE 2.

Occurrence of V. cholerae in three sample fractions (water, small plankton, and large plankton) as determined by the enrichment and DFA O1 methods

Season	Enrichment method								DFA O1 method
	Site F		Site B		Sites K, S, and H		Cruise sites		Site F		Site B		Sites K, S, and H
	% Positivea	nb	% Positive	n	% Positive	n	% Positive	n	% Positive	n	% Positive	n	% Positive	n
Winter 1998	0.0	6	NDc		0.0	18	ND		0.0	6	ND		0.0	18
Spring 1998	11.1	9	ND		29.6	27	ND		22.2	9	ND		22.2	27
Summer 1998	6.7	15	ND		97.8	45	ND		13.3	15	ND		75.0	44
Autumn 1998	ND		ND		ND		ND		22.2	9	ND		7.4	27
Winter 1999	ND		ND		ND		ND		0.0	9	0.0	5	7.4	27
Spring 1999	0.0	9	22.2	9	0.0	27	ND		0.0	9	0.0	9	26.9	26
Summer 1999	27.8	18	16.7	18	11.1	54	0.0	27	16.7	18	66.7	18	20.4	54
Autumn 1999	0.0	9	22.2	9	7.4	27	18.5	27	0.0	9	77.8	9	22.2	27
Winter 2000	14.3	7	0.0	9	4.8	21	ND		14.3	7	22.2	9	0.0	21
Summer 2000	ND		ND		ND		23.7	36	ND		ND		ND
Total	11.0	73	15.6	45	27.9	219	15.2	90	11.0	91	42.0	50	24.7	271

^aPercentage of positive samples.

^bn is the number of samples collected.

^cND, not determined.