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PCB's and Marine Mammals

Credit: Amy Lizee

Telegraph Cove resident orca's

Pollution is a growing concern for the population of marine life that exist in the worlds oceans. One of the most affected marine mammals are whales, orca’s or killer whales to be precise. On a recent trip I took to Telegraph Cove I discovered that killer whales have been found to be the most contaminated marine mammals in the world.

Synthetic chemicals such as PCBs, which have long been banned in Canada and the US for years, are a long-lived industrial compound used to insulate electric transformers and capacitors. Slow to degrade, PCBs float in the air and water, permeate soil and accumulate in animal fat. Since the highest concentration of these chemicals remain in the world oceans, the effects are devastating the orca population and will continue to do so until at least 2030.

Credit: Amy Lizee

Family of resident Killer Whales at Telegraph Cove

There are three groups of killer whales which are: resident, transient and offshore orcas. The classifications of these different groups are based on their diet. While resident killer whales tend to survive off of fish, transient and offshore orcas, which are found deeper in the ocean and away from the shore, feed off of seals, sharks and small whales. Not only does their diet make them very different from their resident cousins, but also makes them more at risk for pollution and accumulation of toxins in their system. Since the PCB and similar chemicals accumulate in the animal fat, the transient and offshore orcas are in the most danger as they are at the top of the food chain.

To give you an example of this type of accumulation, here is the following food chain example:

Fish -> Bigger Fish -> Seal -> Small Shark -> Killer Whale.

Starting at the lowest stage, once the small fish ingest these toxins they continue to stack up the food chain to the killer whales who are considered one of the top marine predators. These toxins continue to build up and can devastate the longevity of a killer whale. While the PCB’s do not cause death, they make whales more vulnerable to infectious disease, impair reproduction, and impede normal growth and development.
As I learnt on my whale watching trip at Telegraph Cove, the effects of PCBs present a greater risk to male killer whales. Since nursing mothers pass some of the PCBs stored in their blubber to their calves through fat-rich milk, they are able to deplete the concentration of PCBs in their system every 3 – 5 years. Males however have no way to eliminate the PCBs they take in from contaminated fish and continue to accumulate toxins throughout their lives.

Credit: Amy Lizee

Killer Whales at Telegraph Cove, BC

According to Dr. Peter Ross a research scientist with the Institute of Ocean Sciences in Sidney, B.C., and lead author of a new study titled High PCB Concentrations in Free-Ranging Pacific Killer Whales, Orcinus orca. "These killer whales can now be considered among the most contaminated marine mammals in the world.” Dr. Ross also goes on to explain that “[her] study shows PCB levels in the fat of transient males averaged 251 parts per million. That means these animals are about 400 to 500 times more contaminated than humans.”