were obtained with non-toxic Van Dorn or Niskin samplers. Aliquots of 

 100 ml were enriched with sterile media and incubated under a fluorescent 

 light panel at constant temperature aboard ship. The flasks were placed 

 in a walk- in incubator described below upon return to the Laboratory. 

 All cultures were grown in the following enrichment medium, 

 potassium nitrate 10 milligrams 



potassium phosphate (dibasic) 2 milligrams 



ethylene diamine tetraaceticacid 1 milligram 



tris (hydroxymethyl) amlnoethane 0.1 milligram 



soil extract 5 milliliters 



sea water 100 milliliters 



The sea water used in the culture medium was collected from the Florida 

 Current, Mlllipore filtered and sterilized and contained 9+1 milligrams of 

 strontium and 0.5 micrograms of cesium per liter. The radioactive isotopes 

 used were carrier-free and did not statistically Increase the total content 

 in the sea water. The soil extract was prepared from soil obtained from a 

 sandy mangrove swamp area, this extract contained less than 0,227o strontium. 

 The cultures were grown in 125 milliliter, Erlenmeyer flasks at 22 + 1°C and 

 illuminated with General Electric cool-white fluorescent lamps. The light 

 intensity was maintained at 300 foot candles for 18 hours each day. Unialgal 

 cultures were established from these mixed cultures by single cell isolation. 



For the investigation of the accumulation of strontium and/or yttrium, 

 five stock cultures of oceanic phytoplankton were used. Two unialgal cultures, 

 Gymnodinium simplex (Lohman) and Katodinium rotundata (Lohman) along with three 

 mixed cultutres designated as 4000A, 35A and lOGC , were used. The mixed 

 culture 35A contained K. rotundata and other phytof lagellate while lOGC 

 contained both K. rotundata and G. simplex and other small flagellates. 



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