SSRN: UNCLASSIFIED CHAPTER1 OBJECTIVE AND BACKGROUND For Operation Ivy the Marine Survey Unit, Project 11.5 of Task Group 132.1, had as major objectives the evaluation of the contaminatior of Hving organisms following Mike shot and an investigation of the residual radiation contamination of the fauna and flora of Eniwetok Atoll from the previous weapons tests. Since Eniwetok Atoll has been used for several tests of atomic weapons since the last resurvey by the Applied Fisheries Laboratory group in 1948, it was essential to establish the level and kinds of residual radiation from the previous tests before the detonation and resultant contaminaticn of Mike shot. The data on the preshot contamination were obtained from samples of flora and fauna of the Atull and the lagoon. In addition to the data accumulated regarding the level of radioactive contamination, it was necessary to determine the condition of the animal and plant populations in the areas chosen for sampling stations. The extensive coastruction program on the Atoll since 1949 not only changed the surfaces of the islands but also modified many of the marine areas. Following Mike shot the studies were directed to the evaluation of 1. The determination of the extent of the area contaminated. 2. The nature and kinds of the radioactive materials found in the various areas. 3. The amount and kinds of radioactive substances absorbed or adsorbed onto theplants and animals, 4. The more immediate effects of Mike shot upon the plants and animals.