In an estuary a zooplankton consumes a phytoplankton with a small globule of PCBs attached to it. A fish consumes the zooplankton as well as many other zooplankton. A larger fish consumes the small fish and then a gull consumes the larger fish. The increased concentration of the chemical at the top of the food chain is an example of biomagnification. bioaccumulation. synergistic properties. PCB persistence. synergistic interactions.