328 <• " OsriiM 111» und Ovi-; I'm i.skn. 



ficasid i;rc'ally in llic roiirsc of Ihe sunimer owiiii^ to llie inilow 

 ol" IVc'sli wmUt IVom tlu' iiK'lliiig siiow of Ihc kmd, so llial on llic siir- 

 lacr il was l)roiii;lil down to (IC) IS", on al llic ciul ol" .luly, at llic 

 same lime lliat the leinperatuie rose to ."iti" — 4i)C, tlie ellccl ol' 

 Nviiicli was lliat the marine organisms were for a great part killed, 

 and only the resling-spores of diatoms were living. The samples from 

 this period really contained in the main freshwater organisms, which 

 had hecn carried ont hy Ihc freshwater from land, for example, 

 Coehislnini microporuni , (ioniphosphacria lacuslris, Anabaena sp., 

 Spiroldeiiid sp., Staiirasiruiu sp.. Hyalotheca sp., and many freshwater 

 diatoms. In August — Seplemher the salinity again rose and the 

 temperature sank (ca. 27 — 28"mm) and ca. 0°), and at the same time 

 the freshwater forms disappeared and marine species ruled again. 

 The samples from Octoher 19(H) permit us to conclude, that the sali- 

 nity continues to rise, most prohably owing to the formation of ice, 

 and the temperature to fall, just as they presumably show the de- 

 mise of the plankton (see abovei. 



The planton of Danmarks Havn is thus an arctic 

 coast- j)lank ton with a flowering period of short dura- 

 lion in late summer. It is somewhat poor in species and con- 

 sists mainly' of neritic diatoms, which have a wide distribution in 

 northeiii seas, also outside the arctic region. Truly arctic are pro- 

 bably only the following species, none of which were very abundant 

 in the samples: Bacterosira fragilis, Eucampia groenlandica, Chaeto- 

 ceras gracile, Biddiilphia arctica, Navicnla septentrionalis, N. Vanhöffenü. 

 Peridininni islandiciiin, P. breuipes, P. catenatiim, Gonijaiilax triacantha, 

 Tintinnopsis karajacensis, T. pellucida and Tintiiinns vitreus. 



II. Plankton of the drift-ice and coastal waters, 

 a. August 1906. (Table Ilj. 



The samples (11) belonging here were collected during the period 

 from July 31sl to August KUh in the ice-filled waters; they fall natur- 

 ally into two groups: 



The outermost group (5 samples) are from water with a temper- 

 ature of —0-7° to — 1-9°C. and a salinity of :31-2— 32-8^oo and they 

 were taken between ca. 6^ — ll'' W. L. (ca. 120 — 180 miles from the 

 coast). The plankton is very uniform in all the samples; it consists 

 mainly of diatoms and tintinnids; the most frequent species are 

 Chaetoceras coiwohitiiin, Rhizosolenia hebetata f. semispina, Rh. obtusa, 

 Cyttarocijlis denticulata typica and robusta, Peridiniiim siibinerme, 

 P. curuipes and P. pelliicidum. Characteristic, though occurring in 

 smaller quantities, were Coccolithophora pelagica (dead), Pontosphaera 

 borealis. Dinophysis arctica, Peridiniiim roseum, Dinobryon pelliicidum 



