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SUMMARY OF SECTION II
Levels of activity of the plankton for the eastern lagoon were de-
termined nine times in 1954-1958.
26,
The first observed level on March
1954, 25 days after the Bravo detonation at Bikini, expressed in
microcuries per kilogram of planktonic ash, was about 2,000.
By
mid-December 1954, it had declined to 50, and by late October 1955,
to 6.
Fallout from the Redwing series raised the July 1956 levels to
approximately 100.
In July 1957, levels were still between 15 and 100,
but by early March 1958 they had declined to 0.3.
Fallout from the
Hardtack series raised the August 1958 levels to only 0.8
the last observation.
-4 uc/kg ash,
The decline rate, disregarding the two peaks fol-
lowing Redwing and Hardtack, but including their later residual effects,
was steep, with a slope of -3.5.
From the plankton data for the years 1954-1957, it was shown that
results were nearly twice as consistent when based upon ash as upon
wet weight, and that there was no significant difference in activity between samples taken with fine-and coarse-meshed nets.
On the ash
weight basis, the levels of plankton in 1955 at Ailinginae Atoll were no
higher than at Rongelap Atoll, whereas they were higher on the wet
weight basis.
Decay slopes of pre-Redwing plankton ranged from -1.6
to -2.4, while the decline slope for the plankton of the lagoon as a whole
over this period was -3.5, so that the decline was more rapid than the