THE BLACK SEA 427 



In our general estimation of the biomass and productivity of the Black 

 Sea plankton we have to accept that these data are high and of the same order 

 as those of the Caspian Sea, which is completely confirmed by V. Wodjanit- 

 zky's (1941) opinion on the high biological productivity of the Black Sea. 



Pelagic community. Some regions of the Sea, remote from the shores and 

 mainly within the convergence zones, are inhabited by an original pelagic 

 biocoenosis described by B. Iljin (1933) and somewhat resembling the Sar- 

 gasso Sea fauna, since it consists of large gatherings of floating plants, but, 

 in contrast to the Sargasso Sea, these are dying eel-grass leaves brought 

 out by currents from the shores. As has been described by Iljin, among the 

 mass of floating material live many animal-forms, which have specially 

 adapted themselves to this environment. Among them the more common 

 ones are : pipefish (Syngnathus schmidti) ; stickleback (Gasterosteus aculeatus) ; 

 the isopod (Idothea algirica), and large crab megalops (probably Liocar- 

 cinus holsatus and Portunus arcuatus) ; and at times in large numbers grey 

 mullet larvae, young fry, and the young of the year; anchovy {Engraulis 

 encrasicholus), sprat {Spratella sprattus phalerica); pipefish (Syngnathus 

 schmidti) and the predators feeding on it; mackerel (Scomber scombrus); 

 Sarda (Pelamys sarda); Tuna (Thymus thymus), and dolphin (Delphinus 

 delphis). All these forms have typical characteristics of pelagic organisms ; it is, 

 however, unknown whether stickleback can spawn away from the shores, 

 while grey mullet forms part of this biocoenosis only when young. Among the 

 birds the stormy petrel is always present. 



S. Maljatzky has established (1940) the existence of several areas of abun- 

 dant gatherings of living organisms in the northern part of the eastern half of 

 the Sea ; he thinks that these areas are connected with the areas of increased 

 vertical circulation. 



Not only an increase in the amount of zooplankton but a huge shoaling 

 of pelagic fish — anchovy, sarda and also dolphins — is observed in these areas. 

 This is also the spawning ground of both these fish (Fig. 207). The fact that 

 the spawning grounds of anchovy and sarda are always separate may be 

 due, Maljatzky thinks, to a mass devouring of anchovy by sarda. 



Benthos and Nekton 



The qualitative composition of phytobenthos. The qualitative composition of 

 Black Sea macrophytes was investigated by N. Voronichin (1908) and 

 E. S. Zinova (1936); N. Morozova-Wodjanitzkaja (1927-41) has done much 

 comprehensive research on its ecology and chiefly on its quantitative distri- 

 bution. 



At present there are 236 known species of green, brown and red algae. With 

 the passage from the Mediterranean Sea to the Black Sea the macroflora is 

 much less impoverished than the animal forms ; only with the passage into 

 the saline waters of the Sea of Azov does the number of species of the bottom- 

 living algae drop markedly, as is shown in Table 174. 



Apart from the algae two species of flowering plants — Zostera marina and 



