TABLE 1.

Separation of phytoplankton and bacteria by prefiltration^a

Sample	Positionb	Sampling depth (m)	Date	Filter typec	Chl. a		Cyano		Bacteria		Carbon ratio (%)e based on:
					Concn in SW (μg liter−1)	% in filtrated	No. in SW (103 ml−1)	% in filtrated	No. in SW (105 ml−1)	% in filtrated	Chl. a data	Cyano data
Oceanic
Southern (south)	65°24′S, 140°40′E	40	18 June 1995	8AU	0.48	0.37	<0.03	—f	2.9	93	1.4	<0.01
Southern (north)	48°32′S, 146°23′E and 47°46′S, 146°41′E	4	25 June 1995	8AU	0.49	0.65	8.0	<0.4	6.0	96	4.3	<0.2
Subtropical Pacific (south)	14°52′S, 155°10′E and 12°59′S, 154°53′E	4	4 Feb. 1995	8AU	0.078	17.8	0.97	<6	5.8	91	11	<2
Subtropical Pacific (north)	15°20′N, 141°24′E and 16°27′N, 140°20′E	4	10 Feb. 1995	8AU	0.10	8.2	0.67	<10	6.6	87	5.6	<3
Equatorial Pacific	0°02′S, 150°42′E and 1°35′N, 149°34′E	4	7 Feb. 1995	8AU	0.21	0.99	35	<0.2	8.3	92	2.3	<4
Transitional north Pacific	31°20′N, 140°25′E and 32°22′N, 140°13′E	4	12 Feb. 1995	8AU	0.23	0.52	3.2	<3	5.4	94	0.90	<3
Coastal
Tokyo Bay	35°08′N, 139°46′E	1	30 July 1996	8AU	11.8	0.32	—	—	61	81	0.93	—
Otsuchi Bay	39°21′N, 141°59′E	2	2 June 1995	GF-75	7.2	0.26	23	2.7	21	67	3.0	1.1
	39°21′N, 141°59′E	5	5 June 1995	GF-75	4.1	0.26	37	2.3	20	72	1.8	1.0
	39°21′N, 141°59′E	10	17 May 1996	GF-75	4.2	4.7	—	—	33	37	86	—
	39°21′N, 141°59′E	10	20 May 1996	GF-75	3.6	2.6	—	—	29	23	15	—

^aComparisons of chlorophyll a (Chl. a) concentrations and cell abundances of cyanobacteria (Cyano) and bacteria are made between whole seawater (SW) and filtrates. 

^bSome samples were taken while the ship was steaming. In these cases, positions at the beginning and end of sampling are reported. 

^c8AU, Micropore 8AU; GF-75, Advantec GF-75. Nominal pore sizes are given in Materials and Methods. 

^dPercentage of the chlorophyll a concentration or the number of cells (cyanobacteria or bacteria) in whole seawater that passed through the prefiltration filter. 

^eRatio of carbon in phytoplankton to total organic carbon in the concentrated samples; calculations were based on a carbon-to-chlorophyll a ratio of 50 and a cyanobacterial carbon content of 200 fg cell⁻¹. Chlorophyll a concentrations and cyanobacterial abundances of concentrated oceanic samples were calculated from those in prefiltered samples by assuming that the concentration factors of chlorophyll a and cyanobacteria are the same as that of bacteria (see the text). 

^f—, not determined.