biomagnification

Biomagnification is the process by which the concentrations of certain substances increase as they move through successive trophic levels in a food chain. It is distinct from bioaccumulation, which describes the buildup of substances within an individual organism from all sources over time. Biomagnification occurs especially for persistent, fat‑soluble chemicals that resist degradation and are not readily excreted.

The mechanism involves organisms at lower trophic levels acquiring contaminants from the environment or from consumed prey. When these organisms are eaten by predators, the contaminants transfer to the predator and are not efficiently removed, leading to higher concentrations in the predator’s body. Over time, this can produce substantially higher concentrations in top predators than in the surrounding environment. The effect is most pronounced for persistent organic pollutants and certain heavy metals, particularly methylmercury.

Common examples include organochlorine pesticides such as DDT, polychlorinated biphenyls (PCBs), and other persistent pollutants. Mercury, especially in its methylated form, can also biomagnify in aquatic food webs, resulting in elevated levels in large fish and apex predators. Metrics used to study biomagnification include the trophic magnification factor (TMF) and related bioaccumulation factors.

Impacts are ecological and potential health risks. In wildlife, high contaminant levels can affect reproduction, growth, and behavior, while in humans, exposure through diet—especially fish and seafood—can pose neurological and developmental risks. Mitigation focuses on reducing releases, limiting environmental persistence, and applying advisories to minimize exposure.