Biomagnification

Biomagnification is the rise in the tissue concentration of a contaminant at successive levels of a food chain, so apex predators carry far higher burdens than the water or their prey. Methylmercury is the textbook case: trace levels in seawater concentrate up to dangerous loads in long-lived predatory fish such as tuna and swordfish, driving seafood consumption advisories. It depends on the contaminant being persistent and fat-soluble.