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Marine Microbiology 



(pore size 0.45 ± 0.02 /i) has been assigned a value of 100. This 

 method of expression was used because this porosity is now 

 widely used, and our interest is centered on retention by smaller 

 and larger porosities in comparison with this standard size. 



•/.ACTIVITY RETAINED (HA MILLIPORE ■ 100 %) 



Fig. 1. The retention by nets(« 35 x 35 /x mesh; D 106 x 106 /i mesh) 



of natural phytoplankton communities labelled with C^* compared to the 



activity retained by 0.45 /j,±0.02 jx filters. 



In Figure 1 the relative retention of net material and of 

 the HA Millipore filter is compared. With the exception of two 

 observations in East Sound, the nets retained less activity than 

 the 0.45 /'. filter. There is no obvious trend in the relationship— 

 in fact, the scatter is considerable, with approximately two-thirds 



