Bioaccumlation in tuna Bluefin tuna are among the fishes that were exposed to radioactive material released into the sea by the damaged Fukushima nuclear power plant (Section 47.1). These tuna breed in the western Pacific, and some migrate to the Eastern Pacific when they are 1 to 2 years old. Daniel Madigan suspected that migrating tuna would transport radioactive material to the waters off the coast of California. To test this hypothesis, he and his collaborators analyzed the concentration of cesium radioisotopes (¹³⁷Cs and ¹³⁴Cs) in bluefin tuna and yellowfin tuna caught near San Diego in August 2011. Yellowfin tuna do not cross the Pacific; they spend their lives in California's coastal waters. The scientists compared these data with the radioisotope content of bluefin tuna that had been caught near San Diego in 2008. FIGURE 48.9 shows their results.

FIGURE 48.9 Radioactive cesium (Cs) concentration in two species of tuna caught along the coast of California.

¹³⁷Cs has a half-life of 30 years and some persists in the Pacific from weapons testing. ¹³⁴Cs has a half-life of 2 years and was undetectable in the Pacific prior to the accident at Fukushima. Becquerels (Bq) is a measure of radioactivity.

Does the data support the hypothesis that bluefin tuna transported radioisotopes from Fukushima in their body?

To determine: Whether the data supports the hypothesis that bluefin tuna transported radioisotopes from Fukushima in their body.

Concept introduction: Bioaccumulation is the concentration of a pollutant inside an organism’s tissues causing the amount of the pollutants to increase over time. Trophic level also affects the pollutant concentration by the process of biological magnification. The concentration of the chemical increases in the ecosystem as the pollutants move up the food chain. Bioaccumulation and biological magnification even in low concentration of the pollutant (depending on toxic potential) can have detrimental effects on a species.

The powerful earthquake occurred in the northeast coast of Japan in March 2011 caused tsunami that killed 15,000 people. During this time, the nuclear power plant on the shore of the city Fukushima became damaged and released some radioactive materials into the air and sea. The water was polluted with cesium 137 (¹³⁷Cs), a radioactive material having a half-life of 30 years.

The bluefin tuna are among the fishes that were exposed to radioactive materials released into the sea. These tuna fishes breed in the western Pacific and some migrate to the Eastern Pacific when they are 1 to 2 years old. Researcher D suspected that the tuna might have transported the radioactive materials off the coast of California. To test this hypothesis, the concentration of cesium radioisotopes (¹³⁷Cs and ¹³⁴Cs) in bluefin tuna and yellowfin tuna caught near the San Diego in August 2011were analyzed for the presence of cesium.

The yellowfin tuna reside in the California’s coastal water and they do not cross the Pacific. Therefore, the presence of cesium in yellowfin tuna was compared with bluefin tuna...