Some Relationships of Phytoplankton to Enviroiiment 277 



at the surface, but more usually at 25 m and frequently at 50 

 m. In the open sea, in the Coral and North Tasnian Seas, the 

 highest concentration occurs between 50 and 100 m, frequently 

 extending through this depth range, and occasionally at 150 m, 

 at which depth phytoplankton is frequently quite plentiful. In 

 the Southern Tasman, however, phytoplankton is more concen- 

 trated in 25 to 50 m of water, and the maximum has been found 

 at the surface, at some stations, (see cruise data Gascoyne 2/60 

 and 1/61 C.S.I.R.O. Station Lists). 



Both vertical distribution and total numbers of phytoplank- 

 ters may vary diunially (Tables 1 and 2), with a maximum in 

 the daytime, not necessarily at the same hour, and a minimum at 

 night. Table 1 shows that this variation is not resti'icted to photo- 



TABLE 1 



Fluorescent and Total Counts of Phytoplankton Collected at Depths 

 OF 1, 25 and 50 M IN 60 m of Water to Study Diurnal Variation 



Coefficient of variation approximately 36 per cent. 



TABLE 2 



Fluorescence Counts of Phytoplankton from Surface 

 Samples Taken from a Ship at Anchor 



