Chapter 1 



I 



Domain of the Marine Microbiologist" 



Claude E. ZoBell 



11 order to set the stage for the following papers, my as- 

 signment is to make a few generalizations regarding the marine 

 environment as a habitat for microorganisms. Among tlie many 

 kinds of microorganisms considered are bacteria, actinomycetes, 

 yeasts, fungi, blue-green algae, certain diatoms, dinoflagellates, 

 microflagellates, some of the simpler protozoans, and viruses. 

 Just as there is no well defined demarcation between microorgan- 

 isms and macroorganisms, there is likewise a gradual merging 

 of marine with brackish and fresh water environments, particu- 

 larly in marshes, bays, estuaries, rivers, inland seas, and lakes. 

 Most inland waters find their wav into the sea, and infonnation 

 gained from the study of inland and coastal waters contributes to 

 an understanding of conditions in the sea. 



The sea has been described as a gigantic biochemical labora- 

 tory or chemostat in wliich a great diversity of organisms function 

 together and in competition with each other for the sparsely con- 

 centrated nutrient substances. The kinds of organisms present, 

 their abundance, characteristics, and acti\'ities are influenced by 

 each other as well as by environmental conditions. As contrasted 

 with other major habitats, the marine milieu is distinctive in its 

 vast area and volume, its low content of organic matter, relatively 

 high salinity, low temperature and high pressure at great depths. 



The marine microbiologist is concerned with the qualitative 

 and quantitative evaluation of tlie physiological activities of 

 microorganisms that influence the state of carbon, nitrogen, sulfur, 

 phosphorus, hydrogen, oxygen, and other elements in the sea 



* Contribution from the Scripps Institution of Oceanography. New Series. This 

 work was supported in part by grants from the Office of Naval Research, Task 

 No. NR 103-020, 



