Phytoplankton → Zooplankton → Aquatic insects → Insect-eating fish → Fish-eating fish → Man

Minamata is a disease that occurs due to methyl mercury poisoning. In the above food chain, the highest concentration of methyl mercury shall occur in

Nonbiodegradable toxic substances, often present in industrial waste waters, can undergo biomagnification in the aquatic food chain. Biomagnification refers to increase in concentration of the toxicant at successive trophic levels. This happens because a toxic substance accumulated by an organism cannot be metabolised or excreted and is thus passed on to the next higher trophic level. This phenomenon is well-known for mercury and DDT.