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Risso's dolphin at surface

My lucky number – 13 years studying amazing Risso’s dolphins

Everything we learn about the Risso's dolphins off the coast of Scotland amazes us and...
Dead sperm whale in The Wash, East Anglia, England. © CSIP-ZSL.

What have dead whales ever done for us?

When dead whales wash up on dry land they provide a vital food source for...
Risso's dolphin © Andy Knight

We’re getting to know Risso’s dolphins in Scotland so we can protect them

Citizen scientists in Scotland are helping us better understand Risso's dolphins by sending us their...
Pilot whales pooing © Christopher Swann

Talking crap and carcasses to protect our planet

We know we need to save the whale to save the world because they are...
Fin whale (balaenoptera physalus) Three fin whales Gulf of California.

Speaking truth to power – my week giving whales a voice

The International Whaling Commission (IWC) meeting is where governments come together to make decisions about whaling...

Why do whales and dolphins strand on beaches?

People often ask me 'why' whales and dolphins do one thing or another.  I'm a...
A spinner dolphin leaping © Andrew Sutton/Eco2

Head in a spin – my incredible spinner dolphin encounter

Sri Lanka is home to at least 30 species of whales and dolphins, from the...
Orca (ID171) breaches off the coast of Scotland © Steve Truluck.

Watching whales and dolphins in the wild can be life changing

Whales and dolphins are too intelligent, too large and too mobile to ever thrive in...

Mayday Monday – Legacy Toxins and Bioaccumulation

Primary Threat #2: Legacy Toxins and Bioaccumulation

Chemical pollution is another major threat to the orcas: the Southern Resident orcas are one of the most contaminated marine mammal populations in the world. They are a long-lived top predator, which makes them incredibly vulnerable to pollutants that accumulate up the food chain. Their home in Puget Sound is very urban, and toxins that originate on land make their way to the rivers and coastal habitats where they are absorbed by tiny plankton – these plankton are eaten by small baitfish and work their way up the food web to the salmon that orcas eat. At every step in the food chain, the concentration of contamination is compounded, a process called biomagnification. 

Toxins of greatest concern are the “persistent organic pollutants” or POPs, such as the pesticide DDT, PCBs (a known carcinogen) and PBDEs, (flame retardants). Exposure to these chemicals is linked to disease in orcas because they depress the immune system and act as endocrine disrupters that cause reproductive problems. These chemicals are known as “legacy toxins” because of their tendency to persist in the environment. Both DDT and PCBs have been banned in the US, but are still present in alarming concentrations in whales’ blubber layer. Because these toxins are found in reproducing females, calves will continue to be exposed to – and accumulate – these same “legacy toxins” for generations to come. Young whales have particularly high toxin levels that they acquire from their mothers, who use their fat stores to help the growth and development of their calves. The health of new babies is compromised from the beginning because of this toxin offloading between mother and calf. The level of PCBs found in the blubber of Southern Residents greatly exceeds the level we know to be detrimental to other marine mammals. High levels of toxins play a prominent role in preventing them from increasing at the rate needed for recovery.

The three pods differ in their levels of each specific toxin: L and K have higher levels than J pod of DDT, which is more likely to occur off the California coast, indicating that these two pods spend more time feeding on prey there – an area not included in critical habitat but part of the proposed expansion. The National Marine Fisheries Service (NMFS) has collected fecal samples from the Southern Residents as they travel the outer coast, which could provide new information about their contaminant levels, but samples from the past three years have yet to be analyzed and the results made public.

While DDT and PCBs are banned in the US, chemical pollution is still an issue because of historic use, retention in blubber, and their use in developing countries where they still enter the ocean and circulate to west coast waters. Critical habitat will not directly help to remove threats associated with toxin exposure and accumulation, but will help manage the ongoing harmful human actions that affect the Southern Residents, and adds protection from any future activities that may result in more toxins entering their habitat. The severity and persistence of these toxins makes it all the more important that we take what actions we can to lessen other stressors.

Help us expand the Southern Residents’ critical habitat by signing our letter urging NMFS to act NOW.

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