The highest DDT concentration in aquatic food chain shall occur in

Biomagnification is also called biological amplification. It is a phenomenon in which certain harmful chemicals get accumulated in the tissues of organisms in higher concentrations through the food chain. Biocides including pesticides, fungicides, insecticides, rodenticides, and herbicides show biomagnification.

Thus, in a food chain beginning at the marine ecosystem, harmful chemicals (DDT) that are deposited into the oceans, which are transferred to the plankton. These zooplanktons are fed on by smaller fish, which are in turn consumed by larger fish. These larger fish serve as the food for birds of prey like seagulls and hawks. Due to biomagnification, the highest quantity of DDT will be found in these birds.