608 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



area and, apparently, in the southeasternmost part of the Sea. Zostera is 

 easily detached from the bottom by the swell and, since it floats, it gets 

 scattered throughout the Sea, often forming heaps of wrack in places distant 

 from that of its original growth. The main accumulations of the second form 

 —Polysiphonia sertularioides —ате recorded in the southeastern parts of the 

 Sea. 



Charial algae (Chara intermedia, Ch. polyacantha, Ch. aspera and Ch. 

 crinita) grow in huge amounts on the shallow (0-2 to 2 m) hydrogen sulphide 

 silt soils of the eastern coast, mostly in inlets and behind the islands, etc. 

 Macrophyte sea-weeds in the Caspian Sea do not sink deeper than 25 m 

 owing to the poor transparency of its waters. The biomass distribution of algae 

 is very patchy, rising at times almost to 30 kg/m 3 with the growths of charial 

 algae and sometimes dropping to insignificant amounts ; it is adapted mainly 

 to within 2 m of the surface. Zostera nana biomass reaches 1 kg/m 3 at some 

 places, but is commonly about 200 to 300 g/m 3 (wet weight). Total raw re- 

 sources of this commercial plant constitute about 700,000 tons of wet weight 

 in the Caspian Sea. Its yield in the area of the Apsheron peninsula alone is 

 about 1-5 to 2 thousand tons. Red algae are especially abundant along the 

 western coast of the Caspian Sea. OffSvinoi Island they have a biomass of up 

 to 3-6 kg/m 3 , consisting mostly of Laurencia paniculata. In other areas the 

 red algae Ceramium diaphanum and Polysiphonia sertularioides predominate. 

 Among the green algae Enteromorpha ampressa and Cladophora spp. are 

 preponderant with their biomass of a few kilogrammes. Charial algae give 

 2 to 3 kg/m 2 biomass in some areas. Brown algae do not form any consider- 

 able biomass in the Caspian Sea. The total biomass of Caspian macrophytes 

 is of the order of 3 million tons of wet weight, with an average PjB ratio 

 about unity. A chart of the macrophyte biomass of the eastern shores of the 

 Caspian Sea is given in Fig. 286. 



The maximum macrophyte biomass is found in the Caspian Sea near soft- 

 soil shores, the minimum near rocky floors. This has led Kireeva and Shcha- 

 pova to assume that the Caspian is more of a lake than a sea by the distribution 

 of its phytobenthos biomass. 



Qualitative composition of bottom-living fauna. As has been mentioned above, 

 the Caspian Sea fauna is considerably inferior in its variety to that of the open 

 sea, both in the total number of its species and in the relationship between its 

 separate component groups. Table 256 contains some plankton-benthos and 

 plankton groups. 



The difference between the composition of the marine and Caspian Sea 

 fauna is shown in Table 257. 



It is evident from this table that in full-salinity seas Porifera, Coelenterata, 

 Polychaeta and Bryozoa form groups as varied as those of the molluscs, 

 crustaceans and fish, while in the low-salinity waters of the Black, Caspian 

 and Baltic Seas the last three groups constitute only 50 to 65 per cent of the 

 groups mentioned. Moreover one of the greatest characteristics of the 

 Caspian Sea — the poverty of its qualitative composition — is shown graphic- 

 ally in Tables 257 and 258. 



