in the same concentrations as in the pools: 

 no additions, biotin (0.05ug/l00 ml), thiamin 

 (10.0 ug/lOO ml), cyanocobalimin 

 (0.015 ug/lOO ml), methionine (l mg/100 ml), 

 cystine (l mg/lOO ml), and Tween 80 

 (l mg/lOO ml). Bacterial plates were poured 

 as usual with the yeast extract -peptone agar 

 both before and after the eight -hour 

 incubation period. After ^.5 hours of 

 incubation at 25 ± 1°C in the illuminated 

 rater bath, 5,222,500 counts/minute of NaHC^Oo 

 tfere added to each bottle. 



rhe results of this experiment, using both 

 Light and dark bottles, are presented in 

 rable 18. 



Little can be concluded from this experiment. 

 Che most stimulatory addition for C^-^02 

 fixation in the light was 0.15 mug/ml of 

 :yanocobalamin (vitamin B]^) which increased 

 :1^02 uptake by a factor of 1.3 compared to 

 the untreated control in the light. The only 

 3ther significant difference from the untreated 

 :ontrol was where 10 ug/ml of the sulfur- 

 :ontaining amino acid, cystine, was added, 

 rtiich depressed the Cl 1 ^ fixation by 4-9 c /o in 

 :he light. 



Phe addition of 10 ug/ml Tween 80 doubled the 

 lark fixation. Methionine inhibited the dark 

 lptake of C 1 * by 58%. 



l?he bacterial numbers were not influenced by 

 the organic growth factors to any appreciable 

 axtent, but the addition of Tween 80 increased 

 the bacterial population by a factor of 2.5 

 is compared with the untreated control in the 

 Light. Most of these supplements stimulated 

 aacterial development in the light as com- 

 pared to the untreated control. The bacterial 

 levelopment in the dark was greatest in the 

 antreated control and in the presence of 

 [Veen 80. 



DISCUSSION AND CONCLUSIONS 



In the series of experiments presented, an 

 attempt was made to determine whether certain 

 Drganic substances (NO3, P]0^, and trace 

 slements) and certain organic pools (vitamin, 

 amino acids, purines and pyrimidines, Tween 80, 

 yeast extract, soil extract, etc.) would 



"trigger" increases in the C-^Og assimilation 

 processes of the phytoplankton or in the 

 bacterial populations in tropical Pacific sea 

 water. These experiments were carried out 

 immediately after water samples were collected. 



Vitamin pools in the concentrations employed 

 did not stimulate C 1 ^ fixation by the 

 phytoplankton samples from the tropical Pacific 

 Ocean. In most cases the Cl^02 uptake was 

 considerably inhibited by the vitamin pools in 

 the light (Tables 15-17). It is interesting 

 to note in Table 17 where the vitamin pools were 

 tested separately for their effect on the uptake 

 of Cl^ by the phytoplankton, that vitamin pool 

 1 was slightly stimulatory compared to the 

 untreated control, vitamin pool 2 exerted little 

 influence, and vitamin pool 3 was inhibitory. 

 One of the constituents of vitamin pool 3 is 

 menadione. Dam (19^) has demonstrated that 

 this vitamin is inhibitory to photosynthesis 

 in Chlorella due to direct toxic action on the 

 cells. This fact coupled with the observation 

 that various individual vitamins such as thiamin 

 and cyanocobalamin actually stimulated CIW2 

 fixation by the phytoplankton (Table 18) to a 

 small extent, suggests that the vitamins as a 

 group are not inhibitory to C^-^C^ fixation in 

 the light but that various inhibitory constitu- 

 ents of the vitamin pools may mask the effects 

 of other members of the pools. Vitamin pools 

 were not inhibitory to bacterial development 

 in any case. However, where the individual 

 vitamin pools were added to separate bottles 

 (Table 17), there was almost no stimulation 

 from any of the pools as compared to the 

 untreated control. In other experiments there 

 was some indirect information suggesting that 

 vitamins were stimulatory to bacterial 

 development (Tables 15 and 16) . Generally, the 

 vitamin pools were not as stimulatory as the 

 other organic pools tested (amino acids, 

 purines and pyrimidines) . 



The purine and pyrimidine pool enhanced the 

 development of marine bacteria and increased 

 the Cl^0 2 uptake of the phytoplankton (Tables 15- 

 17) . Purines and pyrimidines in natural waters 

 have received little attention from previous 

 investigators, but some evidence exists 

 suggesting the limited distribution of the 

 pyrimidine, uracil, and an unidentified purine 

 in pelagic sea water (Vallentyne, 1957; 



- 96 



