~~: 14 activity extending from Bikini to Eniwetok and continuing westward to the southwest corner of the sampling area. The highest ct eee levels along this line were greater than 50,000 c/m/g in the area from Eniwetok to about 35 miles westward. In the area sur. veyed, the lowest values were in the northwest quadrant, with the minimum value, 1,300 d/m/g, at the most northwesterly sta- tion, 1A, at 14° N - 159° E. The plankton tows were made to a depth of about 200 meters, which assured complete sampling of the stirred layer. It is generally accepted that the stirred layer exists only above the thermocline, Ne a region in which temperature decreases rapidly, with increase in depth. Bathythermograph casts were made at each station to determine temperature changes with depth and we “ ey Same mileate neehaar Rehdoem NA a wee eee nee : amples of bathythermograph traces are shown in Pigure ll. Ex- Sur© ellen ASA ce ne ee from these data the area of the thermocline was determined. face temperatures were approximately 81° to 83°F and remained practically unchanged to a depth of about 300 feet; feet temperatures decreased, below 300 and at the 450 foot level were 709 to 74°F, indicating that, in general, the upper limit of the aan thermocline was just below 300 feet or about 100 meters. Water: | The radioactive content of the water samples from the fifty-three collecting stations 1s presented in Table l. The sums of the values of radioactivity of the residue from one | liter of sea water and of the filtered water, less KO for each station and depth are given in Table 2. Table 3 summarizes the percentage contribution of each component to the total radio- 28 . Pe activity for all stations at each sample depth. Usieiciie. UNW. Or Vee... . : aS j ne TMi TONES, - #34 3

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