Biomagnification refers to the increase in the concentration of toxic substances in organisms at each successive level of a food chain.

In simple terms, small organisms (like plankton) take in a tiny amount of a pollutant (such as mercury or DDT) from water or soil. When a small fish eats lots of those plankton, the pollutant level in its body becomes higher than in the water. A bigger fish then eats many small fish, and a bird or human might eat the big fish, so the top predator ends up with the highest concentration of the toxin.

Biomagnification usually involves chemicals that:

  • Do not break down easily in the environment (they are “persistent”).
  • Are stored in fatty tissues and are not easily excreted or degraded inside the body.

Because of this, top predators (including humans who eat contaminated seafood) can suffer health problems like nervous system damage, hormonal disruption, and higher risks of some diseases due to these accumulated toxins.

TL;DR: Biomagnification = toxins getting more concentrated as you go up the food chain, from producers to top predators.