284 



Marine Microbiology 



SKELETONEMA COSTATUM 



O ASPARAGIN POPULATION 



X ASPARAGIN OXYGEN 



a CONTROL POPULATION 



A CONTROL OXYGEN 



Fig. 5. Effect of asparagin on oxygen production and growth of Skeletonema 



costatum. 



ficial for Dwmliella but adverse for Skeletonema and glucose 

 and glycine seemed slightly inhibitory. 



In each case, where beneficial effects were observed, these 

 increased with concenti^ation up to 1 X IQr^ g per liter. 



These experiments, admittedly of a preliminary character, 

 do suggest possible reasons for the selective growth of certain 

 species such as is observed in phytoplankton blooms. 



CONCLUSIONS 



The presence in the open ocean of numerous particles could 

 be an important ecological factor in phytoplankton distribution, 

 due to soi'ption phenomena associated with the smaller micro- 

 organisms, with nutrients and with metabolites. 



There is evidence that, in unifonn water, horizontal distri- 

 bution of microorganisms may be reasonably unifonn, but that 

 there is a diurnal variation in numbers, and possibly in their vert- 

 ical distribution. 



Salinity-temperature relationships of many organisms are 



