| March 31st, 2015
The cause of recent whale deaths in the Salish Sea sparked scientific debate. Some scientists believe pollutants may play a role.
Killer whale J-32’s body was found floating in the tide near Comox, British Columbia, with her almost full-term calf entombed inside her. The cause of recent whale deaths in the Salish Sea sparked scientific debate, however some scientists believe pollutants may play a role.
The southern-resident orca population of the Puget Sound area is one of the most contaminated marine mammal species in the world. The levels of pollutants found in the killer whales’ bodies are so high, they are considered hazardous waste when washed ashore. The southern-resident orca population has been steadily declining since the late 1990s. Although the cause of this decline cannot be attributed to a single source, it is believed that the lack of food available for the killer whales and high levels of contaminants are contributing to their low numbers.
Ken Balcomb, director and principal investigator for the Center for Whale Research stated in the preliminary necropsy report that killer whale J-32’s blubber was ‘relatively thin and dry of oil,’ which is consistent with malnourishment.
Killer whales consume 70 percent chinook salmon, according to a 2009 report on the relationship between contaminants found in chinook salmon and resident killer whales.
Chinook salmon are the largest and fattiest of all the salmon, so killer whales gain more energy from chinook than any other salmon species, said Brad Hanson, a wildlife biologist for the National Oceanic Atmospheric Association.
However, these southern-resident orcas are suffering because the salmon population is so abysmal, said whale biologist Deborah Giles.
According to the preliminary necropsy report, when the killer whales are not able to consume a sufficient amount of food, they are forced to metabolize their blubber layer. The toxic contaminants stored in killer whales’ blubber are then released into their bloodstream. According to the 2009 report, these contaminants are linked to reproductive impairment.
Contaminants can also be passed down from the mother to the calf while it is in utero, Giles said. It is estimated that 50 percent of first-born calves do not survive past their first year because their mother has passed down her lifetime supply of contaminants to her new calf, Giles said.
“If we look back, this whole story starts in World War II, which was the dawn of the chemical revolution,” said Peter Ross, director of the ocean pollution research program at the Vancouver Aquarium.
Contaminants such as DDT and PCBs were created in the 1940s for use of insecticides and fire-resistant oils, Ross said.
Although PCBs and DDT were banned over 40 years ago, the toxins have a long lifespan and are still found in the waterways, Ross said.
It is estimated that it will be around another hundred years before PCBs and DDT are out of the killer whales’ systems, Ross said.
However, these are not the only contaminants the southern-residents need to worry about, said Ross. There are other harmful contaminants that have not been banned and are still in use today, such as PBDEs that are commonly used as flame-retardants, Ross said.
Flame-retardants are found on numerous household items, including furniture and mattresses, said Scott Redman, the deputy science and evaluation director at at Puget Sound Partnership.
These contaminants, DDT, PCBS and PBDEs, belong to chemical family known as persistent organic pollutants, more commonly known as POPs, Ross said.
POPs biomagnify, which means they increase when traveling up the food chain, Ross said.
Animals at the top of the food chain, like killer whales, are the most vulnerable to POPs, Ross said.
These pollutants contaminate the ocean by being released as dust particles or vapor into the air and then making their way into the waterways, Redman said.
Rainwater can also wash pollutants from paved surfaces and roadways into the water systems — known as stormwater runoff.
Stormwater runoff is the primary way that pollutants get into the Puget Sound, said Julann Spromberg, toxicologist and fisheries biologist at the Northwest Fisheries Science Center.
During rainfall, creek water levels can rise from about 15 centimeters to 1.2 meters, and around 90 percent of that water is runoff, Spromberg said.
Chinook salmon’s role in the food chain
Chinook salmon accumulate more contaminants than other fish or salmon in the Puget Sound area because they have lifespan of four to seven years and are higher on the food chain, Ross said.
However, killer whales regularly feed on a species of resident chinook salmon, known as blackmouth, artificially bred in the 1970s to increase recreational fishing in the Puget Sound, Ross said.
These blackmouth salmon are referred to as “residents” because they live in Puget Sound for the majority of their lives, and not in the open ocean like most chinook salmon, Ross said.
Blackmouth salmon had three to five times higher concentrations of PCBs than six other populations of chinook salmon along the West Coast, according to a 2009 study conducted on PCB accumulation.
“When you are looking at POPs, there are really two dominant things you have to consider,” Ross said. “Number one is how high are you on the food chain, and number two is where do you live?”
Blackmouth salmon have such high levels of contaminants compared to other chinook because they live most of their lives in the polluted waters of Puget Sound, Hanson said. Killer whales accumulate most of their pollutants from this specific type of chinook salmon.
How people can help
In the meantime, individuals can minimize their own personal pollution, Redman said.
“We have found contaminants that come from personal care products, furniture, vehicles, pretty much a wide variety of things you interact with in your daily life,” Redman said.
People can minimize their POP output by being aware of what they are buying and how they are disposing products that contain the toxins, he said.
Redman said the best solution is to try and avoid using products with pollutants and to read the consumer labels to consider what kind of toxins are potentially washing off clothing and ending up in the watersheds.
Killer whales bodies are basically a reflection of the contaminants that have, and are, being released into the Puget Sound and surrounding areas, Ross said.
“So when you have a healthy population of whales in the Puget Sound that eats salmon that means the whole area, the whole ecosystem, is healthier,” Giles said. “Which will obviously benefit humans.”