D 



J 



Fig. 



cell 



out 



violacea 



T2T 



J ff 



Time, hours 



14r 



J 



19. Consumption of natural ^"^C-labeled bacterioplankton containing 

 aggregates (B) and the same bacterioplankton with aggregates filtered 

 by a membrane filter (A) by a fine filter feeder--the sponge Toxadocea 

 (1) and a coarse filter feeder-- the oyster Crassostrea gigas 

 radioactivity of labeled bacteria in water, 10-^ desintegrations 

 ml . 



R = 

 per minute/20 



Using the ^^C-labeled bacterioplankton, the optimal concentrations of 

 bacterioplankton for the nutrition of coarse and fine filter feeders were 

 determined (Fig. 21). For the coarse filter feeders, the optimal 

 concentration of bacterioplankton is that at which the bend occurs in the 

 corresponding curves, at 1-1.5 g/m"^. These values are characteristic for 

 littoral eutrophic marine biotopes or the layers of maximum concentration 

 of plankton in highly productive upwelling zones (see Table 5). In these 

 waters, even coarse filter feeders can supply their nutritional needs by 

 eating bacterioplankton. For fine filter feeders, the optimum 

 concentration is 0.2-0.4 g/m-^. These concentrations are found in the 

 layers of maximum concentration in boreal waters in the summer, the neritic 

 waters of boreal and tropical areas, and the pelagic zone near the tropical 

 divergences. Thus, over a significant portion of the ocean, fine filter 

 feeders can fully satisfy their nutritional needs by means of 

 bacterioplankton alone. 



The bacteria are as 

 assimilation of phytopla 

 Pavlova, Sorokin, 1970; 

 daily rations of fine fi 

 veligers, Appendicularia 

 bacterioplankton amount 

 expenditures of these an 

 weight. Therefore these 

 expenditures by feeding 

 less than the optimal (P 

 Sea cladoceran Penilia a 

 which the crustacean can 

 only 50 mg/m-^, significa 

 the littoral zone. 



similated to 40-60%, close to the level of 



nkton (Sorokin, 1968; Sorokin et al . , 1970; 



Pavlova et al . , 1971; Petipa et al . , 1974). The 



Iter feeders with small body size, such as the 



, Cladocera, hydroids when feeding on 



"to 50-100% of their body weight. The daily 



imals for metabolism amount to 15-20% of their body 



animals can compensate for the metabolic 

 with bacteria at their concentration 3 to 5 times 

 avlova, Sorokin, 1970). For example, for the Black 

 virostris , the threshold concentration of food at 



compensate for its metabolic loss was found to be 

 ntly lower than the biomass of bacterioplankton in 



Special studies of the role of bacterial nutrition have been 

 undertaken for bottom filter feeders of the tropical shelf. These 



279 



