In the spring and early summer of 1962 a large amount of seaweed was washed up on the beaches of the northern Gulf of Mexico. The Sargassum heaps were weakly radioactive due to the presence of fallout. The radioactive elements from fallout (gamma emitters) included cerium, ruthenium, and zirconium- niobium. Beta radiation from the accumulated seaweed was roughly comparable to the total atmospheric precipitate during February over an area of approximately 800 to 1300 square miles in the Gulf of Mexico.