THE BLACK SEA 449 



Table 183. Depth of lower limit of benthos, m, and area of sea-bed occupied by benthos, 



km 2 



Off In Off Off Off 



western northwestern southern Crimean Caucasian 

 coast part coast coast coast 



Depth 125-127 115-125 130-135 127-135 135-165 



Sea-bed area 12,500 57,600 9,500 6,800 6,000 



L. Yakubova pointed out (1935) that of the individual forms Modiola phaseo- 

 lina penetrates deepest (180 m); then came Amphiura stepanovi (165), Neph- 

 thys hombergii (162); Cerianthus vestitus and Melinna palmata do not quite 

 reach such depths. Terebellides stroemi, Syndesmya alba, Cardium simile, 

 Mytilus galloprovincialis and Phoronis go down as far as 130 m. Eugyra 

 adriatica (125 m) and Suberites domuncula live in rather shallower waters. 



Quantitative distribution of zoobenthos. As distinct from all the other seas of 

 the European part of the u.s.s.r., we possess only scarce data on the quanti- 

 tative distribution of the Black Sea bottom-living fauna. For the purpose 

 mentioned we can use only certain indications from the works of V. Wod- 

 janitzky (1941), V. Nikitin (1938), V. P. Vorobieff (1938), L. Arnoldi (1941) 

 and O. Mokievsky (1949). 



As has been mentioned in the introductory chapter, the high summer 

 temperature of the surface layer of the Black Sea brings about, especially in 

 the enclosed bays, a high intensity of biological productivity. In summer on 

 free surfaces, growths give a biomass of up to 30 or 40 kg/m 2 . A thick pile of 

 30 to 35 cm diameter may be destroyed almost completely by marine borers 

 in the three summer months (July to September). * The rock-burrowing molluscs 

 are represented in the Black Sea by four species : Petricola lithophaga, Barnea 

 Candida var. pontica, Pholas dactylus and Gastrochaena dubia (V. Nikitin, 

 1951). Uninterrupted colonies of Barnea Candida var. pontica and Pholas 

 dactilus with a population-density of up to 2,500 specimens/m 2 have been 

 discovered on the bare marl shale off the Caucasian shores. 



M. Dolgopol'skaya (1954) has given the results of her experimental research 

 on fouling in the Black Sea. The total annual weight of the fouling is up to 

 100 kg/m 2 ; the main fouling organisms are: balanus, sea-mussels, bryozoa, 

 ascidians and oysters. V. Wodjanitzky has pointed out (1941) that on mussel- 

 shell gravel at 10 to 25 m deep the benthos biomass can reach 3-7 kg/m 2 and 

 is often 1-5 to 2-0 kg/m 2 . A biomass of up to 60 g/m 2 is obtained on the sand 

 floor off the coast, and on the mussel-mud up to 250 or even 500 g/m 2 .f 

 On phaseolin ooze the biomass varies from a few grammes to 800 g/m 2 . 



* According to P. Ryabchikov (1957) three species of teredinids have been observed in 

 the Black Sea : T. navalis, T. utriculus and T. pedicillata. 



t O. Mokievsky has observed (1945) along the western coast of the Crimean peninsula, 

 on the beach sand above sea-level, abundant colonies of crustaceans (Orchestia), mol- 

 luscs {Donacilla cornea) and polychaetes {Ophelia bicornis) with a biomass of over 0-5 

 kg/m 2 . 



2f 



