24 30 



25 5 



1500 

 2000 



25 OS 



25 5 



Figs 5-7. Vertical distribution of: 1 1 1 water temperature in C';(2)dissolved 

 oxygen in mg/1 (3) total bacteria count in millions of cells/ml; and 

 (4) CO assimilation h> bacteria in darkness, in g C 1' d' 1 . All 

 daia applj to the western Pacific. 



The bacterioplankton distribution over the water column 

 in the western Pacific exhibited some temperature stratification, 

 with several bacterial population and acti\ it) maxima present 

 (Figs. 5-7). Three bacterioplankton concentration peaks were 

 quite clearly in evidence: the first one lay below the /one of 

 maximum phytoplanklon synthesis at a depth of 45 m. the 

 second above the upper boundary of the thermoeline at a depth 

 of 100 ill. and the third at 1.500 m. Elevated microfloral 

 acti\ it} was noted in the euphotic /one (10 15 ml. above the 



I nl ml nl 



mil iimi m layei 



Station 121 Station 122 Station 123 Station 124 Station 125 Station 126 



JL nl n I rn I 



Station 121 Station 122 Station 123 Station 124 Station 1 25 



■ to in layei 



in l.000-2.(HMi,n layei 



Station 121 Station 122 Station 123 Station 124 Station 125 



1 I Bacterial production 



D.0, 



Fig. 8 Bacterial production and organic-matter degradation in the western 

 Pacific. 



thermoeline. and at a temperature drop boundary. This behax ior 

 of bacterioplankton distribution and activity over the water 

 column was closely related to water dynamics and was typical 

 of the oligotrophic waters of the tropical oceans. 



The next series of studies was conducted in the South 

 China Sea. whose waters are more polluted than those of the 

 central Pacific. Analyses of total biomass. bacterioplankton 

 production, and bacterial degradation were performed at five 

 stations. The results of the measurements are presented 

 in Figs. 9-11. These show that the bacterioplankton count 

 in the euphotic layer (0-50 m) ranged from 176 to 

 61 1 x 10' cells/ml '. The highest bacterial population densities 

 were noted for Stations 1 30 and 131. situated in coastal waters: 

 the lowest values were obtained at pelagically situated 

 Station 127. The bacterioplankton count at certain levels of 

 the water column attained 611 x 10' cells ml'. The 

 average bacterioplankton count in this area equaled 

 354 x 10' cells/ml : . 



The bacterioplankton biomass varied over a broad range 

 of values from 3.16 to 11.81 (.tgCl'd 1 . Data for the 0-50-m 

 layer averaged for individual stations yielded values from 6.67 

 to 9. 1 6 jug C I ' d ' . Mean data for bacterioplankton biomass and 

 counts for the euphotic /one place the investigated portions of 

 the South China Sea in the oligotrophic category. 



Low bacterioplankton counts notwithstanding, microflora] 

 activity was relatively high. Thus, the rate of CO. assimilation 

 by bacteria in darkness ranged from 0.52 to 4.07 (ig C 1 d '. 

 averaging 1.60 p.g C 1' d ' for all the areas studied. 

 Bacterioplankton production for individual stations 

 ranged from 1 2.8 to 39.7 p.g C 1 ' d ' (Fig. 1 1 ). The value for 

 the entirety of the area investigated was 26.6 |ig C 1 ' d '. 



The rates of bacterioplankton respiration in the 0-50-m 

 layer calculated as averages for particular stations ranged 

 from 0.11 to 0.34 mg O, 1' d '. The range of bacterial 

 respiration rates for individual samples ranged from 0.07 to 

 0.58 mg O, I'd'. The maximum bacterioplankton respiration 

 rate was observed at Station 1 30. the minimum at Station 1 29. 

 The average daily oxygen uptake by bacterioplankton in the 

 area was 0.23 mg/1 ' . which w as in good agreement with values 

 calculated from experimental data on the respiration of the 

 plankton community as a whole. 



210 



