- 6 



that the dinoflagellate Gymnodinium succeeded the 

 diatom growth or appeared quite late in the experi- 

 ment. This is reminiscent of the way in which dino- 

 flagellates succeed diatoms during the summer in 

 temperate waters. Presumably diatoms or their 

 decomposition products supply some nutritional fac- 

 tor to dinoflagellates. Bacterial turbidity apparently 

 prevented most phytoplankton from growing in the 

 two treatments containing purines, pyrimidines, or 

 amino acids. 



In this experiment two of the three dominant diatoms 

 (Nitzschia and Chaetoceros) and one of the two domi- 

 nant dinoflagellates (Gymnodinium) grew. These 

 three organisms have been carried through several 

 subcultures In the complete medium made up with the 

 original sea water and have now been inoculated into 

 various enriched sea water media in routine use at 

 Scripps. All three algae were successfully brought 

 back from SCOT Expedition and are growing in our 

 culture room. 



TABLE 1 



Growth of pelagic phytoplankton after the addition of nutrients to water 

 samples collected at 10 m depth at SCOT Station 49 ("Dome") 



Days 



Growth : 



Organisms observed microscopically : 



= no growth 



± = questionable growth 



increasing + marks = increasing amounts growth 



T = bacterial turbidity 



(If no symbol, none were seen) 



Ni = Nitzschia 



Ch = Chaetoceros 



G = Gymnodinium 



F = unidentified small flagellates 



