THE LAPTEV SEA 257 



northward from the Lena estuary in 71° 43' N latitude are given in 

 Table 108. 



Evidently the fauna of the upper and lower layers of water would differ 

 greatly. The diluted surface layers of the western part of the Sea spread north- 

 wards for hundreds of miles from the river estuaries and the salinity at that 

 distance is at times 15— 18— 25% . On the other hand the saline waters travel 

 southwards along the bottom troughs. 



After a long, harsh winter, when the waters are almost at freezing tempera- 

 ture, there comes a short summer, and the surface waters of the parts of the 

 Sea freed from ice are warmed partly by the river waters, partly by the sun, to 

 a few degrees (up to 4°) above zero. But the polar ice limit is not far away 

 even in the summer. 



III. FLORA AND FAUNA 

 According to the investigations of K. Derjugin (1932), M. Virketis (1932), 

 I. Kisselev (1932) and A. Popov (1932) the Laptev Sea plankton and benthos 

 have the composition given below. 



Table 109 



Flagellata 6 Conjugatae 4 



Peridineae 28 Diatomaceae 61 



Chlorophyceae 25 Cyanophyceae 24 



Total 148 



Qualitative composition of phytoplankton 



According to Usachev, the species and forms which have been found in the 

 southern part of the Sea, which is exposed to the strong influence of the Lena 

 waters, are those listed in Table 109. 



In this fairly large selection of forms Kisselev distinguishes first of all the 

 groups of brackish-fresh- water forms (23 per cent), most common within the 

 off-shore, highly diluted region : Aphanizomenon flos-aquae, the species Ana- 

 baena, Melosira italica, M. islandica, M. granulata, Asterionella gracillima 

 and some others. 



The author includes a number of species Diploneis and Navicula in the 

 group of the brackish-water forms (4 per cent). And finally to the group of 

 marine forms (5 per cent) there belong : Thalassiosira baltica, Coscinodiscus, 



R 



