Marine mammals can tell us something about pollution. Like the other inhabitants of the Georgia Basin, including invertebrates, fish, and seabirds, a marine mammalâ€™s biology and ecology influences whether they are at risk for pollution effects or not.
For example, of the killer whales found in the Georgia Basin, the â€œresidentsâ€ eat large amounts of salmon, while the â€œtransientsâ€ eat only marine mammals. Although both whale populations are at risk for persistent environmental contaminants (chemicals that do not break down easily and thus increase in concentration or biomagnify as they move up the food chain), the transient killer whales are the most contaminated because they are at the very top of the food chain.
Many persistent environmental contaminants are stored in the fat or blubber of marine mammals. Unfortunately this means when a female killer whale has a calf, the contaminants stored in her blubber will be passed on to her calf through her milk. This also means that older male killer whales tend to have higher levels of contaminants because they do not release them through the production of milk like females do.
At the top of the food chain, long-lived resident and transient killer whales provide an indication of contamination from both local and global sources, and tell us about the health of the Georgia Basin and northeastern Pacific Ocean. Sadly, both these killer whale populations in the Georgia Basin are some of the most polluted marine mammals in the world.
It is important to remember that in addition to being at risk from pollution in the Georgia Basin, marine mammals might also be affected by other human activities such as noise and disturbance, reduced amount of available prey (food), fishing activities (fisheries), by-catch in nets, and habitat loss.