living matter, not of bacterioplankton as such. The decrease of biomass 

 and activity of microflora in the deeper waters of the pelagic zone of 

 the ocean, indicated by the ATP method, direct counting and assimilation 

 of labeled COo, coincides with the results of the plate counts of 

 heterotrophs (ZoBell, 1946) and measurement of the rate of consumption 

 of ^^C-labeled organic matter by bacterioplankton in samples of deep 

 water (Sorokin, 1970b; Takahashi , Ichimura, 1971). 



One significant peculiarity of marine bacterioplankton is the 

 clustering of a significant fraction (20-30%) of the microbial cells 

 into aggregates (Jones, Jannasch, 1959; Sorokin, 1970a; Seki, 1971). 

 The formation of aggregates measuring more than 5 um in diameter is not 

 a result of the absorption of bacterial cells on the surface of 

 suspended particles, but rather a result of the growth of films or 

 floccules of microcolonies. Their growth is independent of the presence 

 of suspended particles in the water and continues to occur after 

 aggregates already formed are filtered out (Sorokin, 1971a). The 

 formation of organic aggregates under the influence of air bubbles 

 described by Riley (1963b) does not occur in sterile water (Barber, 

 1966) and, consequently, is a result of bacterial activity. The 

 aggregation of bacterioplankton is of important ecologic significance, 

 since it assures that a significant fraction of the bacterioplankton 

 will be accessible to coarse filter feeders such as the calanoids, which 

 dominate in the populations of the pelagic mesozooplankton. 



2 . 3 Microflora of the Bottom Sediments 



The population density of bacteria in the upper layer of the bottom 

 sediment varies as a function of the level of productivity of the region 

 and of depth (Table 5). In the richest sediments of the shelf, the 

 microflora composes as much as 4-6% of the organic matter in the 

 sediment. The maximum values of total population, defined by the method 

 of direct microscopy, is 1-9 -lO^ cl/ml of wet sediment, which was found 

 in shallow eutrophic regions: the lagoons of atolls, the littoral zones 

 of inland seas (Butkevich, 1938; Salmanov, 1968; Novozhilova et al . , 

 1970; Sorokin, 1970c, 1971b, 1973d). The production of bacteria in the 

 sediments of such regions amount to 0.2-1 g/1 of wet sediment, the P/B 

 coefficient is 0.2-0.4. These data indicate the great intensity of the 

 productive activity of microflora in the sediments of the shelf zone, 

 assuring their high food value for the benthic invertebrates. It is not 

 by chance that in this zone, a significant fraction of the benthos 

 consists of silt swallowers. 



In deep-water regions of the inland seas and on the continental 

 slopes of the temperate and tropical regions of the ocean, the total 

 number of bacteria in the surface layer of the soil is 0.2-1. 10*10^ 

 cl/ml, their biomass is 0.1-0.4 g/1, their production--5-50 mg/1 per day 

 (Sorokin, 1964, 1970, 1971c; Anderson, Meadows, 1969; Seki, ZoBell, 

 1967; Salmanov, 1968; Ernst, 1970). In the bottom sediment in deep- 

 water areas of the ocean--the radiolarian and pellitic silts and deep- 

 water clays--the total number of bacteria decreases to 10-50 '10° per ml, 

 the biomass--to 3-30 mg/1, production--to 0.1-1 mg/1 per day. The P/B 

 coefficient is quite low--0. 01-0.1. 



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