of the East Icelandic current, where, at a comparatively high temperature at the surface, the de- 

 velopment of the vernal biological processes was nevertheless delayed. It must be said that in this 

 region the temperature drops sharply with increasing depth. The thermocline is at a depth of 100 

 m. At a depth of 300 m., the temperature drops to 1°. The low temperature in deep waters de- 

 lays the maturing of Calanus as well as its surface concentrations . A still greater delay in the 

 development of plankton is observed in the cold wedge of the waters of the East Icelandic current. 

 The plankton is concentrated in deeper waters or deeper below the surface, in 50-100 m. 



so 



m 



r r J- 4- y y t f r «■ 

 50 tbo im ml 



so- 



soc n^g/n-> ^ 



X 



ao 



200 



m 



( 



400 

 500 



r 2' J" 4- s' «• r «• S" lo- 



130 ^ 



r 2- 3- 4- s- 6' r r r 



^?>l '(^ 



/• f r 4- ! • 



Figure 3. The vertical distribution of the biomass of plankton in relation to temperature 



(4th trip of E/S- "Professor Mesyatsev"). (a) In the waters of the Atlantic cur- 

 rent (station No. 263, April, 1954). (b) In the intermixed waters near the edge 

 of the East Icelandic current ^.station No . 262, March 31, 1954). (c) In the inter- 

 mixed waters at the boundary of the East Icelandic current. At the surface -- 

 Atlantic waters (station No. 274, April 7, 1954). (d) In Atlantic waters (in the 

 southern part of the Norwegian Sea) with a large admixture of the waters of the 

 East Icelandic current (station No. 266, April 2, 1954). 



The formation of spawning accumr 

 (Figure 3b). 



"Calanus in April has not yet been observed 



The instances cited above show that the occurrence of pre-spawning concentrations of Cal- 

 anus differ considerably in relation to regions and depend almost not at all on the increased temper- 

 ature of the surface layers . 



Prior to spawning, Calanus concentrates at the surface, increasing to 400-500 mg/ni3. 



Ill 



