Which element bioaccumulates in tuna?

• A. Mercury
• B. Lead
• C. Arsenic
• D. Cadmium

Answer: (A)

Understanding how contaminants concentrate in food chains is key here. Mercury released into the environment is transformed by microbes into methylmercury, a form that binds strongly to tissues and remains in the edible parts of organisms. In aquatic food chains, this substance accumulates in increasingly higher amounts as you move up from small organisms to larger, longer-lived predators. Tuna, being a long-lived top predator, tends to carry higher methylmercury levels in its muscle tissue than many other fish. This is why mercury is the element most associated with bioaccumulation in tuna. Lead, cadmium, and arsenic can be present in seafood, but they do not biomagnify in tuna to the same extent in the edible tissue, and their patterns of accumulation are different, making mercury the best answer.