relationship in maintaining- and renewing the nitrates for photo- 

 synthetic plants do the activities of these bacteria in the sea 

 bear to the oontrioutions of nitrates and nitrites that the sea 

 receives from its tributary rivers? This question is of direct 

 practical ifflportance if we are to understand the regional variations 

 in the abundance and season of multiplication of floating plants 

 along our coastlines. 



Yeasts and other fermenting organisms have been found in the 

 sea water, although they do not a':pear to destroy su.ears and fats 

 there according to the customary chemical schemes. their existence 

 and enzymic activity there is indicated bv the fact that carbo- 

 hydrates, and fats, like prot-ins, disappear in the sea (just as on 

 land) after the death of the animal or plant. But how do they actual- 

 ly work in different parts or levels of the sea? How do they play 

 their part in m.aintaining the circulation of carbon, the draft on 

 which, by plant growth, must be as constantly replaced, either by 

 the absorption of carbon dioxide from the atmosphere, or by reduction 

 in the sea of organic compounds of carbon to their end states, CO3 

 and water? What part, if any, do bacteria play in the break-down of 

 oil? 



It is because of the generally accepted belief that animal life 

 in the modern ocean depends on the presence of photosynthetic plants 

 for its ultimate food supply, that we have so far stressed the 

 general problems of the role that bacteria may play in keeping the 

 sea water fertile for these plants by maintaining the stock of dis- 

 solved nitrates and nitrites, or by replenishing the water with these 

 substances when they have been locally exhausted. 



But in attempting to interpret the life cycle in the sea, 

 bacteriologists must also take into account another possibility, 

 namely, that the sea may harbor enough bacteria of the sorts that 

 can change carbon dioxide to organic carbon without sunlight, to 

 form an important food for animals and so to short-circuit the line 

 from animal to plant and back to animal. The nitrifying bacteria 

 just discussed fall in this autotrophic cateffory, being'able to ob- 

 tain all their vital requirements from inorganic chemical compounds. 

 And there are other groups of bacteria similarly chemosynthetic ; 

 for example, the methane, hydrogen, carbon monoxide, and sulphur 

 bacteria. Beyond che fact that the nitrifiers and perhaps some of 

 the others do exist in the sea, we have as yet no em.piric knowledge 

 as to how important they are as direct links in the food chain in 

 the sea, or, in fact, what vital rOle they olay there. This ae-ain, 

 is a quantitative as much as a qualitative problem becaiase the' 

 numerical abundance and regional distrioution of such bacteria, more 

 than their chemical potentialities, would ^lovern their importance as 

 direct sources of food for animals, and hence determine the degree to 

 which they free the latter from dependence on the activities of 

 photosynthetic plants. It is with regard to the inhabitants of the 

 abyss where no ordinary plants can exist that this question is the 

 most intriguinQ-, 



We also need to know what part bacteria play in breaklnsr down 

 the refractory organic substances that would accumulate on the bottom 

 of the sea if there were not seme mechanism to disintei^rate them and 

 to bring them into solution in the water. Specifically, what bacter- 

 ia in the sea, if any, are responsible for the mass destruction ox 

 the agar from the stalks and fronds of ssa weeds that is constantly 



