As mercury moves up the trophic levels in food chains, its concentration Stays the same
Increases
Decreases
Is eliminated

Increases

Explanation:

The concentration of mercury will increases as it moves up the food chain because of biomagnification. For example, a school of small fish consumes a minute amount of mercury each, but then a larger fish eats five of the smaller fish. After this the larger fish has more mercury in its system than one small fish because it ate five small fish (along with the mercury in each of the small fish). Now a seal eats multiple large fish. Overall, the seal has the highest mercury concentration out of all the animals mentioned.

Biomagnification is "the concentration of toxins in an organism as a result of its ingesting other plants or animals in which the toxins are more widely disbursed."

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.