Certain Quantitative Characteristics of the Pelagic 

 and Bottom Life of the Ocean* 



L. A. ZEXKEVITCH 



Institute of Ocea>wIogy, Academy of Sciences of the 

 Union of Soviet Socialist Republics, Moscow 



AT present it is impossible to give a sufficiently complete picture 

 of the composition, the vertical and horizontal distribution, the 

 ecology and the history of the pelagic fauna throughout geologic 

 time. This is especially difficult for the abyssal fauna. Therefore, 

 I have taken the liberty of enlarging the scope of my report and 

 have attempted to make generalizations about a number of 

 problems. 



Our knowledge of the systematics of the abyssal fauna is far 

 from complete. According to Vinogradova's (1959) accurate 

 estimate for Spongia, Coelcnterata, Cirripedia, Isopoda, Decapoda, 

 Pantopoda, Asteroidea, Echinoidea, Crinoidea, Holothurioidea and 

 Pogonophora, 189 species have been found in depths greater than 

 4000 m. Bruun (1956, 1957) listed 127 species (exclusive of Forami- 

 nifera and Pogonophora) in depths exceeding 6000 m. This figure 

 should now be doubled with the addition of the Foraminifera (78 spe- 

 cies), Pogonophora (17 species), Echiuroidea (5 species), and other 

 Crustacea and Echinodermata. The qualitative impoverishment 

 noticed in various groups varies with depth. The change in the 

 number of species with depth is also evident for the following 

 groups: Polychaeta, Pericarida, Pogonophora, Asteroidea and 

 Holothurioidea. Furthermore, it is of interest to note that in going 

 from midlatitudes (north and south of 40°) to the equatorial region 

 (between 40°N and 40°S), the total number of species (Table I) 



* This paper has been published previously: L. A. Zenkevitch, Certain quan- 

 titative characteristics of the deep-sea life in the ocean, Isvest. Akad. Naiik 

 S.S.S.R. Ser. Geog. 2, 10-16 (1960). (In Russian.) 



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