Scientists from California State University, Long Beach tested giant kelp collected in the ocean off Orange County and other locations after the March, 2011 accident, and detected radioactive iodine, which was released from the damaged nuclear reactor. The largest concentration was about 250-fold higher than levels found in kelp before the accident. The radioactivity had no known effects on the giant kelp, or on fish and other marine life, and it was undetectable a month later.
Spread in large, dense, brown forests across the ocean off California, Macrocystis pyrifera, known as giant kelp, is the largest of all algae and grows faster than virtually any other life on Earth. It accumulates iodine so Manley realized it would be a useful dosimeter to check how far radioactive material spreads. In addition, giant kelp concentrates radioactive iodine 10,000-fold – for every one molecule in the water there would be 10,000 in its tissues.