As fertilizer from farm fields makes its way into the Chesapeake Bay, a chemical reaction occurs between the nitrogen within the fertilizer and which element found in the water?

Hydrogen

Explanation:

When Nitrogen is introduced into the Chesapeake Bay it combines with the Hydrogen in the water which causes a chemical reaction that creates Ammonia. This is a corrosive compound that is highly toxic and can kill an individual if enough of the gas that it creates is inhaled. The chemical compound of Ammonia is one Nitrogen atom and three Hydrogen atoms to make up the formula NH3.