Table 4. Average concentration of radioactive strontium by 

 marine algae after 48 hours exposure. 



Species or Concentration 



Culture No. Factor 



G. simplex 18.6 + 2.3 



K. rotundata 381.7 + 51.5 



aOOO m A. 21.5 + 4.6 



35 A 24.3+2.6 



10 m G,C. 29.3 +7.0 



2 . The effect of strontium concentration on uptake . 



To find the effect of higher concentrations of strontium on the uptake 

 of the strontium and to determine whether or not the uptake of radioactive 

 strontium had been due to strontium- starved cells, cultures were grown in 

 media which contained up to 110 mg Sr/ liter. Ten microcuries of strontium-90 

 solution was introduced into the actively growing culture (4 days) and the 

 cultures continued for another ^8-hour period. At that time a 10-ml aliquot 

 was filtered onto a millipore filter disc and dried over silica gel. The 

 dry filter discs were counted under a thin-mica window G-M tube. These 

 experiments showed that the addition of higher concentrations (up to 10 

 times natural sea water) of stable strontium had no toxic effect on the 

 culture. The growth of the cultures was as good as those grown in natural 

 sea water. With the exception of K. rotundata the increased concentrations 

 had little effect on the uptake of radioactive strontium (Figure 6). The 

 uptake of K, rotundata seemed to be depressed slightly by the higher strontium 

 concentration . 



3. Uptake of strontium by dead and living cells. 



A subculture of each of the five selected test cultures was allowed to 

 progress into the logarithmic growth phase (4 days), and at that time was 

 heat killed by autoclaving for 15 minutes at 15 p.s.i. Each subculture was 

 then inoculated with 10 jj, c of 3trontium-90 solution, After 48 hours exposure 



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