600 



Marine Microbiology 



AEROBIC HETEROTROPHS IN PELAGIC WATERS 



/ 

 / 



/ 



y 



/ 



Average number of bacteria / ml 



Fig. 3. Aerobic heterotrophs in pelagic waters. 



,1- 



depths. 1,241 colonies were examined on chitin-yeast extract-sea 

 water agar, and of these, four showed evidence of de-grading 

 chitin, or 0.32 per cent. All chitin plates were incubated for at 

 least 30 days. 



The average number of colonies that appeared on chitin agar 

 plates seemed to be generally less than on the corresponding 

 2216e plates, but showed the same relative trends of population 

 size. 



In the evaluation of culturing conditions for chitinoclasts, 

 mentioned above, samples of surface sea water from just beyond 

 the surf zone, at the end of Scripps Institution Pier, La Jolla, 

 California, were plated. On the same media as used in the pelagic 

 studies, 18.9 per cent of the colonies on chitin-yeast extract sea 

 water agar showed clearing zones around the colonies, compared 

 to the 0.32 per cent in pelagic waters. 



Chitinoclasts in Pelagic Zooplankton 



Since so few chitinclasts were found in the water samples 

 from hydrographic casts, efforts were made to examine zooplank- 

 ters. The procedures described above were devised to determine 



