3 days, by which time water contamination had spread over an area of 50 square miles, the dose rate from the water was well within safe limits for persons remaining for brief periods. Yet it was several more days before inspection and scientific parties could spend useful time among the surviving target vessels.

At the bottom of the lagoon, below the point of detonation, Navy divers months later found that the explosion had scooped out thousands of tons of mud and coral sediment, creating a shallow basin half a mile wide. This basin, in the slow settling of returning sludge, became an area from which long-lived radioactivity entered Bikini’s biological system.

First Assessments

In 3 weeks of final work after Test Baker, the Bikini scientific teams took from the islands and the lagoon many hundreds of samples of plants, corals, crabs, fish, plankton, and water. They noted that radioactivity was present in all samples taken from every part of the atoll, which indicated an early uptake of radionuclides by the biota[9] and suggested that there was a continuing circulation of radioactive debris in the water. They took samples of fish in the open ocean outside the atoll and made comparative collections at other atolls. The instruments and techniques for analyzing radioactivity were far from refined, but all available evidence pointed to the need for more particular efforts to examine radiobiological results.

The Bikini Resurvey of 1947

A resurvey of Bikini, the first of many, was conducted with heavy radioenvironmental emphasis in July 1947, a year after the Crossroads tests. The scientific expedition was supported by 2 vessels and included 70 scientists and several hundred Navy personnel.

Bikini Beach as it appeared in the years after Operation Crossroads.

The resurvey group, entering an oceanic environment that had been completely undisturbed for nearly a year, established at once that traces of residual radioactivity still were cycling in Bikini’s ecosystem. For 6 weeks the scientists probed every realm of the atoll environment, sampling biota, making inventories of plant and animal communities, and obtaining core samples from the lagoon floor. When the data had been assembled and reviewed and the reports filed, months later, there was consensus that Bikini had produced no evidence that radioactivity, as a separate and identifiable factor, was having any immediate effect on the health of the atoll, and probably no cumulative effect, either.

There were, of course, unknowns. So long as radioactivity remained in the biological cycles there were possibilities of future developments. In 1947 no other place on earth offered an opportunity to observe the natural processes by which radiation contamination is eliminated from an environment. It therefore seemed prudent to compile a longer record, consisting of other, purely radiobiological surveys at Bikini.

By 1947 the new U. S. Atomic Energy Commission had taken over from the wartime Manhattan Engineering District the management of the national effort in the field of atomic energy. A primary responsibility of the AEC in that period was to press ahead with nuclear weapons development, but the agency also had specific obligations and interests in the fields of biology and medicine. Meantime, the testing of nuclear weapons had been started at a new proving ground at Eniwetok Atoll, 190 nautical miles west of Bikini.

Islands on the rim of Eniwetok Atoll, as they appear today. The marks of man, such as a landing strip, are visible, but regrowth of vegetation is apparent. Note extent of the reef on both sides of islands.

Studies at Nuclear Test Sites, 1948-1958

The first test series at Eniwetok, Operation Sandstone (1948), incorporated no formal radiobiological studies, but radiobiologists visiting Bikini also made surveys at Eniwetok in 1948 and 1949. Then, for a time, world events intervened. The detonation of an atomic device by the U.S.S.R. in 1949 was followed in 1950 by the outbreak of the Korean War, and these events produced a national mood oriented toward national defense. By 1951, because events in the Pacific had interrupted tests there, the Atomic Energy Commission had established a continental test site in Nevada. In that year, too, tests were made at Eniwetok preliminary to the detonation of the first thermonuclear device.

After 1951 each of the test programs had its radiobiological component. In the Pacific, radiobiological surveys were associated with Operation Ivy (1952), Operation Castle (1954), Operation Redwing (1956), and Operation Hardtack (1958). A small field station, the Eniwetok Marine Biology Laboratory, was established for use by scientists conducting biological studies. Bikini was incorporated into the Pacific Proving Ground in 1953, and new biological surveys were performed there in connection with the tests of 1954 and later.

The Eniwetok Marine Biology Laboratory. Monument at right commemorates the battle for Eniwetok in World War II.

In these years, 1951 to 1958, the U.S.S.R. was testing nuclear weapons, as was Great Britain after 1952. Fallout from these contributed to the total of man-made radioactivity potentially available to the environments of the world.

Landmarks

The years between the establishment of the Pacific Proving Ground and the signing of the 1958 nuclear test moratorium were years in which the quest for environmental information could not keep pace with the rapid growth of nuclear capability. But the growth in the field of weapons served to underline the need for information and produced certain landmark developments in environmental research.

The detonation of the first thermonuclear device projected the problem of environmental contamination to the stratosphere and, literally, to every part of the earth. This explosion, Test Mike, largest on earth to that time, was set off on Elujelab Island, on the north rim of Eniwetok Atoll, on November 1, 1952. In the reef where Elujelab had been, the blast left a crater almost a mile in diameter and 200 feet deep. The towering nuclear cloud rose in 15 minutes to a height of 130,000 feet.

Test Mike marked a point of change. Before, fallout from nuclear detonation had been principally local, touching the waters and reefs of an atoll or a desert landscape. After Test Mike, the implications of fallout obviously were global.

A mishap in connection with a 1954 thermonuclear test at Bikini contributed in two important ways to the enlargement of environmental investigations. Fallout from the test, swept off its predicted pattern by unexpected winds at high altitudes, deposited debris on Rongelap, an inhabited atoll east of Bikini, and on fishermen aboard a Japanese vessel operating in the Bikini-Rongelap area. The accident, unfortunate in its consequences at Rongelap and in Japan, had other results of even wider impact. From it came the first international approaches to the problems of ocean contamination and, later, long-term bioenvironmental studies at Rongelap