496 Marine Microbiology 



for the peculiar vertical distribution of ammonia, nitrates, nitrites, 

 hydrogen sulphide, thiocompounds and phosphates in the sea. 

 Due to the use of the comparative quantitative method it became 

 clear that the bottom of the Black Sea is a giant biochemical 

 laboratory, determimng the present day hydrochemical regime 

 of that sea. It must be mentioned that these investigations proved 

 the erroneous nature of some of the conclusions of hydrochemists, 

 as, for instance, the origin of hydrogen sulphide, the fate of the 

 dead organic matter in the Black Sea and the reasons for the 

 presence of thiocompounds in its hydrogen sulphide zone. 



We must not, however, over-estimate the present quantita- 

 tive methods for estimating the physiological groups of micro- 

 organisms. Like other quantitative methods of culturing, they, 

 in relation to the microorganisms living in natural environments, 

 are inaccurate, strongly underestimating the real values. In their 

 present state these methods are useful not for an absolute esti- 

 mate but for a relative estimate of the intensity of microbiologi- 

 cal transfonnations of matter, and only when the gradients are 

 sufficiently steep. We can state that on the bottom of the Black 

 Sea at its greatest depths there is considerably more organic 

 matter easily assimilable by microorganisms than on the bottom 

 of the deep region of the Sea of Okhotsk, since the differences 

 in the numbers of the corresponding physiological groups are of 

 the order of 1000. Smaller differences in the results of examining 

 water and bottom samples can lead to incorrect conclusions due 

 to the considerable experimental error of the methods used for 

 the quantitative study of the physiological groups of microor- 

 ganisms. 



The improvement of the old and the working out of new 

 methods for the quantitative study of the biochemical activity 

 of microorganisms under the natural conditions of their environ- 

 ments is a most important task of microbiology. Progress in this 

 field will allow hydrochemistry to explain many phenomena in 

 the distribution of biogenic substances in the waters of seas 

 and oceans. This also applies equally to the chemistry of the bot- 

 tom deposits of marine habitats, which so far have gained very 

 little from the data of marine microbiology to clarify the processes 

 of diagenesis of various compounds on the bottoms of the seas 



