RESULTS 



nlk r 



In the first experiment, the C O2 assimila- 

 tion and bacterial numbers in surface sea 

 water from a poorly productive area (30*01' N 

 latitude, ll6%9' W longitude) west of Baja 

 California were determined in both light and 

 dark bottles. The samples were incubated for 

 seven hours in the illuminated water bath at 

 l8 + 1*C. The results are shown in Table 13 . 



The C-^Og assimilation in the light was 1.6 

 times that in the dark and the bacterial in- 

 crease was almost four times that in the dark. 

 In this experiment the photosynthesetic activ- 

 ity of the phytoplankton apparently stimulat- 

 ed the bacterial population, presumably be- 

 cause of the metabolic by-products of the marine 

 algae. The importance of the dark-bottle con- 

 trols was emphasized by the 63°/» dark fixation 

 in this experiment. In the rest of the experi- 

 ments dark-bottle controls were utilized wherev- 

 er possible. 



In the next experiment the effect of inorganic 

 nutrients on C^Oo fixation and bacterial 

 populations was determined in poorly productive 

 water just north of the Alijos Rocks west of 

 Baja California (26*50* N latitude, 116*13' W 

 longitude; Station BT - - 7) . NO3, POI4., and 

 PI metals were added to one pair of bottles . 

 Pairs of these inorganic additives were added 

 to other sets of bottles containing the sea- 

 water sample . Soil extract was added in an- 

 other set of bottles to the NOo, POj^, and PI 

 metals as a final treatment. Light- and dark- 

 bottle controls containing no additions to the 

 sea-water sample were incubated at 20 to 2^*C 

 for a total of six hours with the treated 

 samples. After four hours 5,222,500 counts/ 

 minute of NaHC 1 0o were added to each bottle 

 from sterile ampules. The results of thi6 

 experiment appear in Table Ik. 



Little or no effect on C 1 0g assimilation 

 due to the addition of the inorganic elements 

 was observed in this water mass. However, 

 the populations were permitted to adjust to 

 the conditions in each set of bottles for only 

 four hours before adding the NaHC-^Oj, so that 

 the period allowed for the uptake of C 1 ^ may 

 not have been long enough to accentuate the 

 differences in fixation in the different treat- 

 ments, particularly in a poorly productive area 

 such as that under study. 



The results in Table lk regarding the 

 bacteria are not particularly informative. 

 PI metals and POi,. appear to be the most 

 stimulatory to bacterial development in this 

 water, but there is no way to determine from 

 these results whether the increase in bacteri- 

 al populations is due to by-products from the 

 phytoplankton or to direct stimulation from 

 the inorganic substances. In thi6 case, the 

 large number of bacteria in the dark compared 

 with the light supports the results of 

 Steemann Nielsen ( 1955a and b). 



The organic pools were compared with the in- 

 organic additions in the following experiment. 

 A surface sea-water sample from a poorly pro- 

 ductive area south of Alijos Rocks off Baja 

 California (21°3V N latitude, 110* 1*9 ' W 

 longitude; BT - 1 - 5) was treated in duplicate 

 with the following nutrient additions: vitamin 

 pool 1, 2, and 3> purine and pyrimidine pool; 

 KNO3; KgHPO^; and PI metals. The surface sea- 

 water temperature was 28.1+°C. A combination 

 of all of the nutrient additions mentioned 

 above was added to one set of bottles, and 

 all of the vitamin pools, the purines and 

 pyrimidines, and the inorganic additions were 

 subsequently removed from the combined pool, 

 one at a time, in different experimental 

 samples. Finally, another treatment contained 

 KN0., KgHPOi,. and 0.025 ml of Hoagland-Arnon's 

 (1950) trace-element solution. Twelve of the 

 bottles were selected at random and tested 

 for the initial bacterial numbers in the 

 bottles. To each bottle 5,222,500 counts/min- 

 ute of NaHC 1 ^^ were added after four hours 

 of incubation at 30 _ 1*C and the bottles in- 

 cubated for an additional three hours. The 

 bottles were harvested in the usual way and 

 the bacterial counts determined. The results 

 are presented in Table 15. 



The vitamin pools exerted an inhibitory effect 

 on the C 2 assimilation of the phytoplankton 

 in the light. Where the vitamin pools were 

 deleted from the bottles and the purine and 

 pyrimidine pool and the inorganic additions 

 (KNO3, KgHPO^ and PI metals) were added to the 

 water sample, the C 1 ^ fixation was 1.5 times 

 a6 great as the untreated control during the 

 seven hours incubation. Wherever the vitamins 

 were present C-^Og uptake was depressed. 



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