How can pollutants become more concentrated at higher levels of marine food chains?

Pollutants become more concentrated at higher levels of marine food chains through a process known as biomagnification (or bioamplification).12

This ecosystem-level process occurs because certain contaminants—often referred to as persistent, bioaccumulative, and toxic (PBT) substances—possess stable molecular structures that resist degradation by sunlight, microorganisms, or chemical reactions. Because these substances are typically fat-soluble, they accumulate in the fatty tissues and organs of organisms rather than being easily excreted.132

The concentration increases through the following steps:
* Initial Uptake: Contaminants enter the food chain from the environment (soil, water, or sediment) and are absorbed by organisms at the base of the food chain, such as phytoplankton and zooplankton.34
* Dietary Transfer: As predators consume contaminated prey, they ingest the pollutants accumulated in that prey's tissues.34
* Progressive Increase: Because organisms at higher trophic levels consume large quantities of prey over their lifetimes, they accumulate these persistent chemicals more rapidly than they can excrete them. Consequently, the concentration of the pollutant increases progressively at each successive step in the food web.5213

This process can lead to severe health consequences for predatory wildlife and humans, including reproductive failure, neurological damage, and increased cancer risk.52