Chapter 28 



Some Relationships of Phytoplankton 

 to Environment 



E. J. Ferguson Wood 



An my laboratory, attention is directed at the moment to tlie 

 study of phytoplankton in situ, advantage being taken of the 

 furnishing by the Royal Australian Navy of two frigates fitted 

 out as oceanographic research ships. Using these ships, it is 

 possible to collect samples for immediate examination, and at 

 the same time to obtain chemical and physical data as required. 

 This paper gives some results of work to date, and is not 

 intended to present a coordinated picture of phytoplankton 

 ecology. 



THE RELATION OF PHYTOPLANKTON TO 

 TURBIDITY IN THE OPEN OCEAN 



A striking feature of a study of fresh phytoplankton samples 

 collected by centrifugation of 5 liter samples is the large amount 

 of particulate matter which they contain. In the southwest Pacif- 

 ic and East Indian Oceans and adjacent seas, these particles con- 

 sist of two types,— small (1-3 ,a) opaque, and larger (10-30 /') 

 transparent or translucent particles. The ratio of the number of 

 particles to the number of plntoplankters ranges from about 

 3:1 to 2,300:1, with a mean of 213:1 in the Coral Sea. 



Figure 1 shows plots from an oceanic station in the Coral 

 Sea in which, at left, turbidity (extinction coefficient, EK) is 

 plotted against depth, while at right particle and phytoplankton 

 numbers are plotted ( numbers per liter ) . The shape of the curves 

 suggests that turbidity at tlie surface is related to the total num- 

 ber of particles and that the hump in the turbidity curve at 75 

 m is due to the increase of phytoplankton at that depth. The 

 central graph shows T-S relationships. 



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