biomagnification The process by which large, long-lived predators accumulate the highest levels of contaminants (like mercury) by being at the top of the food chain and eating smaller organisms that have lower contaminant loads.

The accumulation of certain chemicals (such as mercury and PCBs) biomagnifies (increases) as they pass through the food chain. This means that a low amount of mercury might be present in fish that eat plants, but higher amounts will accumulate in fish or birds that eat fish. Adverse effects are more likely to occur in birds or fish that eat other animals.

When an animal eats a plant or another animal, it consumes all the contaminants stored in that food. Contaminants can biomagnify in animals that use other animals for food because the concentration increases with each step from prey to predator.