Consider the following biomagnification question (ppm on mass basis). Hg (toxin)

Question

Consider the following biomagnification question (ppm on mass basis).

Hg (toxin) in plant material is 1.6 ppm (average plant mass is 1.54 g)

Mayfly (adult mass 90 mg) eats 5% of its adult mass in plants per day (lifespan=0.5 year)

Fish (bass) eats 25 (toxic) bugs per day, average lifespan is 4 years, adult mass=4 lbs

We eat 8 adult bass/year for 80 years (average mass =70 kg)

Report the Hg concentration in the plant, adult mayfly, adult bass, and adult human and the % increase in Hg as it moves up the food chain.

Explanation / Answer

Biological magnification often refers to the process whereby certain substances such as pesticides or heavy metals move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans. The substances become concentrated in tissues or internal organs as they move up the chain. Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.

The following is an example showing how bio-magnification takes place in nature: An anchovy eats zoo-plankton that have tiny amounts of mercury that the zoo-plankton has picked up from the water throughout the anchovies lifespan. A tuna eats many of these anchovies over its life, accumulating the mercury in each of those anchovies into its body. If the mercury stunts the growth of the anchovies, that tuna is required to eat more little fish to stay alive. Because there are more little fish being eaten, the mercury content is magnified.

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