How does the change in concentration represent biomagnification?

The change of concentration represents bioaccumulation. Biomaccumulation is also known for biological accumulation which means an increase of toxic substances that occurs in the food chain and often comes from substances with a contaminated environment. The food of the organisms that they consume contains chemicals mostly form the industry or pesticides such as polychlorinated biphenyls (PCBs), pesticides such as DDT, mercury and such. When the organism in higher food chain consume the organism or product that contains the toxic chemicals, the chemicals gradually become concentrated in the food chain. And overtime as these are amassed in the higher organism, they will be the ones who will accumulate the most of the chemicals. The result may be deadly.

       First, biomagnification happens when for example, there's a certain quantity of mercury in a lake and the fish gets contaminated.

Explanation:

       After that, imagine that this fish is eaten by a bigger fish, a different species, with a little bit of mercury inside of it too, but it has a concentration. With that, both concentrations are on the big fish now, and after that, the fish is caught by a human, and the human eats it all, but the human has a concentration os mercury inside its body too, and the three concentrations are now in the human, and so on. This change in concentration is called biomagnification.