for 5 minutes. The supernatant was pipetted from the cells and 15 ml of 

 sterile sea water was added. The cells were resuspended in the sterile 

 sea water and the above procedure was repeated three times . When the 

 supernatant was removed after the third centrifugation, the cells were 

 suspended in 2 ml of sterile sea water and added to 52.5 ml of sterile 

 medium in a 125-ml flask. Twelve flasks of each culture were prepared in 

 this way and incubated. After 24, 48 and 72 hours, the cells from three 

 flasks of each culture were centrifuged and washed three times with sterile 

 sea water, filtered onto a tared millipore filter and weighed. 

 Uptake by adsorption of cesium by G. simplex and K. rotundata . In the 

 studies with the uptake of G. simplex it was observed that the rate of 

 uptake was greater during the second 24-hour period than during the first. 

 This would indicate that adsorption played only a minor role in the uptake 

 of cesium by G. simplex . On thee other hand, there was the possiblity that 

 the washing technique prior to filtration together with the distilled water 

 wash of the cells while on the filter disc would cause any cesium to be 

 displaced. Therefore a study of the role of adsorption was made. 



The adsorption study was conducted in the following manner. Two 250-ml 

 Erlenmeyer flasks, each containing 100 ml of filter sterilized M2M medium 

 (enriched soil extract and natural sea water) were innoculated from a unialgal, 

 bacterial-free culture of G. simplex and allowed to grow for several days 

 until a fairly dense algal population was obtained. Since 200 ml of algal 

 suspension was needed the two cultures were mixed an then counted. The 

 procedure used to determine adsorption of the algae was to add constant 

 numbers of cells to a constant amount of the isotope for varying lengths 

 of exposure time. The exposure times varied from 3.5 minutes to 178.5 

 minutes. At the end of the exposure time the cells were removed from the 



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