9 

 The Black Sea 



I. GENERAL CHARACTERISTICS 



The Black Sea may be considered as a tributary of the Mediterranean of a 

 markedly anomalous character which penetrates deep inland. It is connected 

 with the Mediterranean Sea through the Bosporus and the Dardanelles ; it 

 is 3,000 km away from the Atlantic Ocean. Its considerable depth, its great 

 reduction in salinity by the inflow of river water, and an influx of bathy- 

 metric saline waters from the Sea of Marmora create a sharp saline stratifica- 

 tion of the Black Sea waters into an upper layer, inhabited by a rich flora and 

 fauna, and deep masses of water contaminated by hydrogen sulphide. There 

 is very little exchange of water between the two layers. The fauna of the Black 

 Sea consists of three genetically different elements. 



The sections of the Sea with the lowest salinity — inlets and river mouths 

 and the rivers themselves — are inhabited by Caspian relict fauna. Members 

 of the fresh-water fauna move into these parts of the Sea from the rivers and 

 at times become abundant there. 



The Sea, however, is inhabited by the most euryhaline forms of the Mediter- 

 ranean flora and fauna ; the number of species is about four times smaller 

 than that in the Mediterranean. The Black Sea fauna is numerically inferior 

 to that of the Sea of Azov and considerably superior to that of the Mediter- 

 ranean. 



A luxuriant development of the pelagic fauna, enormous growths of red 

 algae, phyllophora and a marked display of filter-feeders (Mytilus, Modiola 

 and others) : such are the biological characteristics of the Black Sea. It is a 

 feeding ground for many Mediterranean fish, while a number of Black Sea 

 fish leavit in summer time, moving to the Sea of A zcv to feed. 



II. HISTORY OF THE STUDY OF THE BLACK SEA 



First period 



The exploration of the Black Sea was begun by the voyages of P. Pallas 

 (1793-94) who devoted the third volume of his work Zoographia Rosso- 

 Asiatica (1811) to the genetic link between the Black and Caspian Sea fauna. 

 In 1858 the Russian ichthyologist K. Kessler worked on the shores of the 

 Black Sea ; he expressed, with remarkable precision, a correct opinion on the 

 geological part of the Black Sea (1874). Kessler arrived at the following con- 

 clusions : (J) at one time the Black, Azov and Caspian Seas formed one single 

 body of brackish water ; (2) the Caspian Sea was separated from the Black 

 Sea before the latter was connected with the Mediterranean ; (3) the migra- 

 tion of Mediterranean fauna into the Black Sea is continuing ; (4) the last 

 phase of the rise in salinity of the Black Sea caused its original fauna to move 

 into the less saline parts of the Sea and into the Sea of Azov. 



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