SIZE-FRACTIONATED PRIMARY PRODUCTIVITY 375 



Assimilation Ratios 



The relationship of productivity per unit of chlorophyll a is 

 known as the assimilation ratio. Current usage of assimilation ratio 

 implies that carbon uptake should be measured at light saturation 

 (Tailing, 1974). During this study light intensity was kept constant, 

 and no provision was made to determine saturating intensities, which 

 are species dependent. For most of the year, the small fractions have 

 the highest assimilation numbers. This is to be expected since small 

 organisms have higher surface-to-volume ratios and, thus, are able to 

 absorb nutrients more readily (Dugdale, 1967). The assimilation ratio 

 has also been said to be a measure of physiological status (Thomas, 

 1970; Eppley, 1972). High ratios tend to indicate that factors such as 

 temperature or nutrients are not limiting. 



The medium fraction consistently had the lowest assimilation 

 ratios. On the basis of size alone, the ratios in this fraction would be 

 expected to be higher than the large fraction. Therefore, they may 

 consist largely of detrital material, damaged cells, or broken 

 filaments from the large fraction, or, alternatively, they may require 

 different temperatures or light intensities. 



The large fraction, although usually intermediate in terms of 

 assimilation numbers, did reach a significant peak in spring (between 

 5.5 and 9.5). 



The size-fractionated assimilation ratios showed some differences 

 among the stations. Stations KWI and REF generally had higher 

 ratios for the small fraction than did stations KD and FRB. There 

 was also a spike in the small fraction at FRB on Sept. 20 which was 

 not apparent at the other stations. The peaks in assimilation numbers 

 were generally higher for station FRB than the corresponding peaks 

 for KD. This could indicate lowered photosynthetic capacity after 

 passage through the plant, 



DISCUSSION 



In this report we address power-plant operation only in relation 

 to the physiological status of entrained phytoplankton. More general 

 discussions on the ecology of the nearshore phytoplankton are given 

 elsewhere (Zeeman, 1977). 



Entrainment Effects 



In this study, we attempted to distinguish between variances 

 caused by sampling methods and true differences in primary 

 productivity among stations by means of both multivariate and 



