well saturated with oxygen (98-102%) and contain a large amount of zooplankton (on the average 

 above 1000 mg/mS). 



330 317 307 

 Station number 



Figure 5. Description of the biomass of plankton in waters of various origins (Station No. 

 330- polar waters; station No. 317- mixed waters; station No. 307- Atlantic 

 waters. Cross-section at 74°20' northern latitude, June of 1954, E/S "Professor 

 Mesyatsev", fifth trip). 



In the area where the waters of the Norwegian current meet and mix with the waters of the 

 East Greenland current, spring was also in full swing at this time . The growing plankton had ex- 

 hausted to a considerable extent the reserves of the nutrient salts of phosphorous (11-15 mg/ni3). 

 Due to the photosynthetic action of algae, the upper water strata were saturated with oxygen (105- 

 119%). "Diatom blooming" can be observed. The plankton biomass is somewhat reduced. It is 

 possible that this resulted from the consumption of the crustaceans by herring. In the mixed waters, 

 schools of feeding herring were often encountered at a comparatively low temperature (1.6-3.5°) in 

 the month of June . We observed in 1955 especially good feeding conditions for herring in waters 

 with a temperatiire below + 2° in the area of Jan Mayen . 



Diatom development comes to an end at this time in the Atlantic waters of the eastern branch 

 of the current. Red Calanus ( Calanus finmarchicus of the in-IV-V stages) are developing. These 

 phenomena characterize the end of the biological spring season . The nutrient salts that were used 

 in the vernal development of j^ytoplankton are being restored (phosphorus 18-23 mg/ni3). There 

 is still a fair amount of plankton on the surface (560 mg/m3 on an average). Its main component is 

 red Calanus , which is the staple diet of young herring (21-28 cm.). According to the material that 

 was collected by us on the third trip of the E/S "Professor Mesyatsev" in June-July, 1953, in the 

 central regions of the Norwegian Sea, it is evident that small herring were predominant in the hauls . 

 Their stomachs were filled with the pink and red young of Calanus . Besides Calanus > the young of 



116 



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