bioaccumulation

Noun B2 – Upper-Intermediate

The gradual build-up of a substance, such as a toxin, inside a living organism faster than it can be removed.

"Mercury undergoes bioaccumulation in fish, reaching much higher concentrations than in the surrounding water."

'Bioaccumulation' in one organism can lead to 'biomagnification,' a related process where concentrations increase further up the food chain.