[Illustration: _Zooplankton, mostly copepods, collected with automatic underwater sampling equipment on board the nuclear submarine_ Seadragon _while cruising under the Arctic ice_.] Other plankton research at Woods Hole uses radioactive carbon-14 and phosphorus-32 as tracers to evaluate rates of growth and nutrient assimilation by algae (floating green plants). These investigations have revealed that the presence or absence of minute quantities of nutrient minerals in seawater affects the rate at which the algae produce oxygen by the process of photosynthesis. Since the energy of all living things—including man—is also made available by photosynthesis, and since most of the photosynthesis on earth is performed by algae afloat in the oceans, it is apparent that this research is of more than academic interest. Algae, the original energy-fixers of the “meadows of the sea”, are also the original food source for the billions of aquatic animals, and may some day prove a source of food for a mushrooming human population. In a project with more immediate application, extensive biological and environmental studies of the Eniwetok Atoll area in the Pacific were conducted prior to the first nuclear testing there in 1948, and these studies have continued ever since. Early in the test series the Japanese, who were at first concerned with the possible contamination of their traditional marine food supplies, were invited to participate in these studies. Fisheries radiological monitoring installations were established in Japan and the U. S. (The latter was established by the AEC and administered by the U. S. Food and Drug Administration.) Neither station encountered any radiological contamination of tuna or other food fish, and the American unit has now been closed. [Illustration: _This shell of the giant clam_ Tridacna gigas _shows the position of a layer of strontium-90 absorbed in 1958 (black line) and in 1956 (white line). The inside of the shell (light layers) was deposited in 1964 when the clam was collected at Bikini Atoll by scientists from the University of Washington, Seattle._] Groups that have cooperated with the AEC in marine radiobiological research are the University of Hawaii, University of Connecticut, Virginia Fisheries Laboratory, University of Washington, U. S. Office of Naval Research, and U. S. Bureau of Commercial Fisheries. At the Bureau of Commercial Fisheries Radiobiological Laboratory in Beaufort, North Carolina, a cooperative effort of the AEC and the BCF is concerned with learning the effects of radioactive wastes on one of America’s most valuable marine resources—the tidal marshlands and estuaries that are essential to the continued well-being of some of our important commercial fisheries. Table III RADIOISOTOPES THAT MIGHT BE FOUND IN AN ESTUARINE ENVIRONMENT Isotope Half-life