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Bioaccumulation and Biomagnification of Toxins in the Marine Food Chain

Work supported by the Trustee Council has contributed significantly to the understanding of how chlorinated hydrocarbons including polychlorobyphenyls (PCBs), and DDT derivatives, bioaccumulate and biomagnify as they move up the marine food chain from phytoplankton to copepods to fish to seals to killer whales. These hydrocarbons are fat-soluble and are not generally metabolized. Instead, they accumulate in the blubber of marine mammals with the result that killer whales have many thousands of times the level of toxins than plankton (measured in parts per million or ppm).

Researchers have documented that transient whales and resident whales in the Gulf of Alaska are genetically distinct populations. While some transients travel throughout the Gulf and are known to prey mostly on marine mammals, residents usually have a more limited range and prey primarily on fish. Because of this, transient killer whales have 10 times or more the concentration of toxins than resident populations. Levels of PCBs average over 300 ppm and DDT levels over 400 ppm in transient killer whales. Calves had especially high levels of contaminants, indicating that contaminants are being passed from mother to offspring.

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