The term "biomagnification" refers to the increase in the toxicant concentration at successive trophic levels.
When a toxic substance that an organism has collected cannot be digested or removed, it goes to the next higher trophic level.
For example - DDT biomagnification in the aquatic food chain.
Through biomagnification, DDT concentrations are increased at successive trophic levels.
For example, a concentration of 0.003 ppb (parts per billion) in water can rise to 25 ppm (parts per million) in fish-eating birds.
DDT at high levels disrupts calcium metabolism in birds, causing eggshell thinning and premature breakage, eventually leading to a bird population decrease.