278 Marine Microbiology 



synthetic organisms but also applies to the non-photosynthetic 

 ones, which microscopy shows to consist chiefly of colorless 

 flagellates. The samples for these tables were taken with the 

 bottom at 30 fathoms in each case, so it may be concluded that 

 there is a variation in the total number of microorganisms in 

 the photic zone. This variation may be due to grazing, to rhythms 

 in reproduction, or both. 



HORIZONAL DISTRIBUTION 



Horizontal distribution of phytoplankton has been studied 

 along the edge of the continental shelf in waters derived from 

 the Coral Sea, and in the southern Coral Sea between Lord 

 Howe Island and Sydney. The results are given in Tables 3 and 4. 



TABLE 3 



Phytoplankton Counts of Surface Samples Taken at the Edge of 

 THE Continental Shelf from a Ship Steaming at 12 Knots 



Time 0830h 0900h 0930h 1420h 1500h 1530h 



Mean count per field 4.05 4.15 4.30 7.0 7.75 7.45 



Standard error 1.81 1.81 1.71 1.34 1.36 1.04 



TABLE 4 



Phytoplankton Counts and Total Microorganisms Occurring on 

 the Surface During a Run from Lord Howe Island to Sydney 



In Table 3, the mean count of phytoplankton per field is of 

 the order of four in the morning, and of seven in the afternoon 

 and the difference at stations twelve miles apart is negligible. 

 The difference between morning and afternoon stations is of the 

 order of that found in studies of diurnal variation, and could 

 be due entirely to this. In this case, the population studied in 

 Table 3 could be regarded as uniform, and, in fact, it consisted 

 of the same plant association, Schroederella delicatiila, Chaeto- 

 ceros secundum, Gymnodinium simplex. 



