se INVESTIGACIONES SOBRE BIOLOGIA MARINA EN LA ZONA DE ENSAYO DE ENIWETOK Resumen En la memoria se resumenlos resultados de las investigaciones sobre biologia marina que se vienen realizando desde 1952 en la zona de ensayo de Eniwetok. A consecuencia de los diversos ensayos nucleares efectuados desde esa fecha se han introducido en el mar una serie de productos de fisidn y otros radioisétopos (237U, 23°Np, 54Mn, *5. 59Fe, 57, 58, 6800p, 65Zn y 185W). El autor indica la concentracién de los radioisétopos en las muestras de plancton tomadas entre cuatro dias y seis semanas despuésde la contaminacidn, asi comola distribucién de la radiactividad entre el plancton y el agua. Los peces herbivoros contenian 65Zn, 55¥e, 57, 58.80C'o y 54Mn. Los peces carnivoros contenian principalmente 55Fe y Zn. MARINE BIOLOGICAL INVESTIGATIONS AT THE ENIWETOK TEST SITE te + a“ Frank G. LowMan LABORATORY OF RADIATION BioLocy, UNIVERSITY OF WASHINGTON UNITED STATES OF AMERICA The disposal of radioactive waste products in the sea is of primary interest to maninsofar as it constitutes a potential hazard in his food materials derived from marine sources. At the present time, the principal source of artificial radioactive elements in the ocean is past weapons tests. In the future, however, the wastes from nuclear power development and the great volume of associated contaminated materials will far surpass the present burden of artificial radioactive elements in the sea. Almost certainly, the radioactive wastes consigned to the sea in the future will be deposited in chemical forms different in varying degrees from those in fallout material. At first consideration comparison of the fates in the marine biotic mass of radioisotopes derived from the two sources might appear to be of limited use. However, investigations on the cycling of radioisotopes through the marine food webs and thelevels of various isotopes in representative samples have been conducted for the past eleven years at the Eniwetok Test Site in areas contaminated by many different types of nuclear devices fired under a wide variety of conditions. The transmission of given radioelements from one organism to another follows similar paths whether the fallout is mixed with calcium compoundsfrom pulverized coralline islands and reefs, or sodium chloride from evaporated sea-water,or is essentially free of either of those nonradioactive materials. Indeed, groups of radioelements with similar chemical characteristics tend to follow similar paths in marine organisms. The uptake of radioisotopes from areas contaminated by fallout is controlled primarily by two factors; the physical factors which determine the distribution of the radioactive material in time and space, and the chemical factors which control : 106