608 Marine Microbiology 



than 50 cells per ml, while the populations found in indixidual 

 zooplankters were frequently several to many orders of magni- 

 tude greater. Even more striking is the comparison of chitino- 

 clastic bacteria, in which only four of 1241 colonies examined 

 from water samples showed evidence of degrading chitin, while 

 in zooplankters chitinoclasts frequently were extremely populous. 

 In the zooplankters examined, the microbes seem to be intimately, 

 possibly internally associated. No attempts were made in this 

 study to establish any commensal or symbiotic relationships be- 

 tween the pelagic zooplankters and the microflora, nor are the 

 data sufficient to establish any taxonomic relationships between 

 the marine animals and the chitinoclastic microorganisms. 



These data suggest the hypothesis that the primary loci of 

 the microbial agents responsible for cycling animal matter in the 

 sea are intimately associated with individual plankters. Jones ( 15) 

 shows similar data with Radiolarians. Bacteria are much more ef- 

 fective physiologically in localized culture than as scattered in- 

 dividuals, and it would seem that a relatively high degree of 

 efficiency in the cycling of nutrients would be maintained. "Dead" 

 organic matter, which results from the death of an organism, or 

 of ecdysis, or excreta, is already amply inoculated with the 

 microbial agents of decay, and probably decay occurs near the 

 original locus of the host. In the case of phytoplankton, the rela- 

 tionship between microbes and host would appear to be primarily 

 sorptive in nature. The concepts of zones or layers of active de- 

 composition would, under this hypothesis, be limited roughly to 

 the degree of zonation of the plankton. 



ACKNOWLEDGMENTS 



Grateful acknowledgment is due to Dr. Claude E. ZoBell for 

 his interest and encouragement as mentor throughout the conduct 

 of this work and the preparation of the manuscript; to Drs. Galen 

 E. Jones, William Berg, and William L. Belser for their critical 

 evaluation of the manuscript; to Drs. Leo Berner and Edward 

 Brinton for their aid in identifying the zooplankters, and for the 

 invaluable assistance of the crews of the Scripps research vessels 

 Orca, Paolina T., and T441. 



