OPERATION II 



Operation II was characterized by an essentially 

 constant temperature gradient, a more diffused distribution 

 of the predominant microorganism Gymnodinium flavum, fewer 

 cells, and a different turbidity pattern. 



The examination of distribution charts and transparency 

 data revealed no consistent patterns or positive correlations. 

 Least-squares data (figs. 8B and D) and the theoretical curves 

 (figs. 9B and D) supported the conclusion that the concentrations 

 of G. flavum cells and total microconstituents were too low 

 to affect transparency in the manner demonstrated in Opera- 

 tion I. Thus, no single microorganism appeared to be a 

 major contributor to light attenuation. Rather, turbidity 

 at this time was the result of a background concentration 

 of G. flavum distributed throughout the water mass, a col- 

 lective distribution of other particulate matter, and, very 

 probably, dissolved organic material, Ceratium furca and C. fusus 

 contributed to specific zones of population density in the 

 distribution of total microorganisms. The distribution of 

 other dinoflagellates, diatoms, fecal pellets, wood fibers, 

 and miscellaneous detritus was not shown to be related to 

 the turbidity patterns. 



Undoubtedly, particles less than 10 microns in 

 diameter, pigments released from decomposing cells, and 

 dissolved organic material, none of which were measured 

 in this study, played a significant role in light absorption 

 and scatter at this time. For example, Burt (1955)® notes 

 that a large share of the particles causing extinction have 

 a radius of less than one micron. 



The contrast between the distribution of G. flavum 

 during the two operations emphasized the role of tempera- 

 ture gradients. The presence of a sharp thermocline during 

 a bloom of G. flavum (Operation I) produced a definite cor- 

 relation between temperature and cell distribution in time 

 and space. The more general distribution of G. flavum in 

 Operation II is believed to have resulted from the absence 

 of a discrete thermal barrier. 



The effect of thermal barriers on phytoplankton 

 distribution may also be a function of timing with respect 

 to bloom period. Provided the rate of cell division at the 



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