GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 



705 



longipes) and other forms are predominant in the surface plankton ; they are 

 replaced in the south by the sea-weeds Rhizosolenia bergonii, Chaetoceras 

 lorenzianus, Climacodium biconcavum, coccolithines, and animals, Cestus 

 amphitrites, Velella, Physalia, Pteropoda and Heteropoda ; and from among 

 the Copepoda members of the genera Herocalanus, Undinula, Copilia, Sap- 

 phirina, Salpas, Halobates and many others. 



Since the convergence zone has no population which is peculiar to itself 



140° 145° 150° 155° 160° 165° 170* 



140 



145 



150 



155 



160" 



165" 



170 



Fig. 339. Distribution of phytoplankton (as percentage 

 of total number of species) in boreal waters, zone of 

 mixing and northern waters of Kuroshio. 1 Cold water 

 species ; 2 Temperate cold water species ; 3 Temperate 

 species; 4 Warm water species. August to October 

 1954 (Bogorov). 



alone in this part of the Pacific, Bogorov thinks that it does not possess the 

 importance of a subtropical zone but only of a ' blending ' zone, of the meet- 

 ing of the tropical and boreal planktons. In the boreal waters north of the 

 convergence zone peridinean sea-weeds constitute about one-third of the 

 total number of plankton species, while south of it the number of diatom 

 species is three or four times greater than that of the peridineans. In the 

 northern part boreal phytoplankton species constitute 79 per cent (I. Smirnov, 

 1956), to the south 0-5 per cent; warm-water species, however, form 93-5 per 

 cent. In general phytoplankton and zooplankton are similar in distribution. 

 Many plankton sea- weeds, among them Rhizosolenia alata and Coscinodiscus 



2y 



