FOREWORD 



It has long been recognized that the sea contains an extensive microbiological 

 population. The microorganisms comprising this population are frequently 

 separated, on the basis of their specific habitats, into planktonic, nectonic, 

 benthonic, and peri phytic forms. The corresponding bacterial populations — 

 and this book deals largely ivith marine bacteria, the diatoms and the protozoa 

 not falling mthin its scope — vary greatly in nature and in relative abu7i- 

 dance, depending upon the geographical, climatic, and other conditions, as 

 well as upon the depth of the water, distance from shore, nature of sea bottom, 

 abundance of plankton, water movement, and a number of other factors. 



Bacteria take part in a number of processes in the sea, including the de- 

 composition of complex plant and animal residues, and the liberation of car- 

 bon, nitrogen, phosphorus, and certain other essential elements in available 

 forms. Since the concentration in sea water of nutrients necessary for the 

 continuation of marine plant and animal life is very limited, such life would 

 soon come to a standstill were it not for the bacteria that keep these nutrients in 

 continuous circulation. Other processes in the sea for which bacteria are re- 

 sponsible are the oxidation of ammonia to ^titrate, denitrification, the oxida- 

 tion of sulfur, the reduction of sulfate, and many others. Bacteria have thus 

 come to be recognized as playing an essential role in the organic production 

 of the sea. However, certain marine processes, in which bacteria appear to 

 take an active part, still remain unsolved. It is sufficient to mention, for ex- 

 ample, the significance of the processes of nitrogen fixation and denitrification 

 in the nitrogen metabolism of the sea, the part played by bacterial cells as food 

 for protozoa and other invertebrates, the symbiotic relationships of bacteria 

 with other forms of life, and the role of bacterial slime in the formation and 

 nature of the ocean floor. 



Marine bacteriology has become as much an essential branch of oceaftog- 

 raphy as have marine zoology, tnarine geology, and physical and chemical 

 oceanography. The marine bacteriologist has much in common, however, with 

 the soil bacteriologist. Both deal with mixed populations of microorganisms 

 rather than with pure cultures; both study the effect of these organisms upon 

 the activities of others. But the marine bacteriologist uses special equipment 

 for obtaining his samples; he deals with a much greater vertical range of depth 

 of natural substrate and with totally different types of interaction between the 

 bacteria and the higher forms of plant and animal life. The physicochemical 

 nature of the soil environment is markedly different from that of the aquatic 

 enviromnent, thus resulting in a different type of microbiological population. 

 Because of this, the marine bacteriologist is not concerfied to the same extent 

 with the numerous fungi and actinomycetes that play such important parts in 

 soil processes. In dealing with a somewhat more homogeneous medium, he 

 encounters less variation in the nature of chemical reactions carried on by the 

 bacteria. 



Although much work has been done and considerable information has been 

 accumulated on the nature and activities of the marine bacteria, the results 



