PHYTOPLANKTON OF SOUTH GEORGIA 29 



Gymnodinium sp. Pyrophacus horologicum 



Phalacroma minutum Ceratium candelabrum 



P. riidgei C. bucephohim 



Dinophysis schuettii C. gibberitm sinistnim 



Amphisolefiia globifera C. limidus 



Goniodoma polyedricum Podolampas bipes 



Peridinium oceaniciim Richelia iiitracellulaiis 

 P. globulus 



THE PHYTOPLANKTON OF THE 

 SOUTH GEORGIA AREA 



The phytoplankton of the area immediately surrounding South Georgia is in general 

 very rich and varied, but the elucidation of the factors governing its quality and quantity 

 is a matter of great difficulty, for a variety of reasons. Foremost among these is the im- 

 practicability of carrying out a series of observations over the whole area continuously 

 throughout the year, so that in considering the seasonal variation in production one is 

 forced to rely on inference from a number of surveys often taken in different seasons. 

 As the conditions fluctuate considerably from season to season, and the phytoplankton 

 crop with them, it will be seen that such inferences must be made with caution. Another 

 factor introducing complicating features is the difli'erent origins of the types of surface 

 water found off' the island, and the considerable mixing which may take place between 

 them. 



Plankton surveys worked in January-February 1930 and in November 1930, together 

 with some material collected later during the season 1 930-1, are described here, and 

 their probable significance discussed in the light of that already made known by Hardy. 

 The positions of the stations made on these surveys are shown in Fig. 4. 



THE PLANKTON SURVEY OF JANUARY-FEBRUARY 1930 



On this survey phytoplankton samples were collected at fifty-seven stations arranged 

 on seven lines radiating out from various points on the island. They were taken between 

 January 20 and February 11, or roughly one month later in the year than the bulk of 

 the material examined by Hardy. The analyses of these samples are contained in 

 Tables H-VHI (Appendix H) in which the stations are arranged in order as they occur 

 proceeding outwards from the island on each line. For the sake of convenience each line 

 has been named after the salient point on shore from which the spacing of the stations 

 was calculated beforehand, but for obvious reasons it was not always possible, or even 

 desirable, to work the stations strictly in this sequence. The tables have been constructed 

 to show the surface hydrology, and the estimated numbers of the several phytoplankton 

 species, together with the totals for the major categories of organisms at each station. 

 In addition, histograms (Figs. 5-1 1) have been constructed showing the total phyto- 

 plankton, and the percentages of the leading forms in the catch at each station. Owing 



