556 Marine Microbiology 



the deep-water stations of the Sea of Okhotsk and the north-west 

 part of the Indian Ocean. Except for the Sea of Crete they are 

 not inferior to the central part of the Pacific Ocean and are only 

 a little inferior (excluding the stations of the Otranto Sti-ait) to 

 the subtropics and the tropics of the Indian Ocean and the 

 Black Sea. 



Taking into consideration that the quantitative development 

 of heterotrophs is determined by the presence of the forms of 

 organic matter assimilated by this group, the main som^ce of 

 which is phytoplankton (1, 2, 8, 10), it can be inferred that the 

 Mediterranean Sea is not poor in this form of life. 



SUMMARY 



Regions of the Mediterranean Sea studied by us differ from 

 one another with respect to the quantitative development of 

 saprophytic bacteria. The richest parts are straits: first, the 

 Otranto Strait and then, the Strait of Tunis. In decreasing order 

 of the number of bacteria present are: the Levant Sea, the Tyr- 

 rhenian Sea, the central part of the Mediterranean Sea, the Ionian 

 Sea and the Sea of Crete. As in other marine basins which have 

 been investigated, microzonation is observed in the distribution 

 of heterotrophs, and no relation has been found between their 

 quantitative disti-ibution at different depths and the vertical dis- 

 tribution of temperature and salinity. The character of distribu- 

 tion of maxima and minima in bacterial numbers at different 

 depths is similar in different stations, and suggests a general 

 stratification of the whole mass in the Mediterranean Sea. As 

 regards the quantity of heterotrophs, the parts of the Meriterran- 

 eon basin studied by us usually exceed considerably the Arctic 

 and the Antarctic regions of the world ocean. With the exception 

 of the Otranto Strait, they are only a little less numerous than in 

 the subtropics and tropics of the Indian Ocean and the Black 

 Sea. The riverflow into the Mediterranean is relatively small so 

 that the main source of organic matter for bacteria is apparently 

 phytoplankton. Thus, taking into consideration the considerable 

 development of saprophytic bacteria, it may be inferred that 

 the Meditenanean Sea is not very poor in plant life. This is in 

 accordance with the data of Bernard ( 3 ) who has found that the 

 southern parts of tlie Mediterranean Sea (from Algeria to Libya) 



