Orca Action Month: What the heck is bioaccumulation?

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June is Orca Action Month, an opportunity to bring together researchers, advocates, and orca lovers everywhere to raise awareness of the threats facing orcas, and to inspire community action to protect the endangered Southern Resident population. Read on to learn more about this year’s theme: Clean Waters, Healthy Futures

With only an estimated 74 individuals remaining and listed as an endangered species in both the U.S. and Canada, Southern Resident killer whales (SRKW) are in danger of disappearing entirely from the Salish Sea. This unique population of whales, with three distinct family groups called the J, K, and L pods, subsists almost entirely on salmon, a preference that evolved at a time when the Salish Sea ran thick with Chinook, their favorite meal. With Chinook numbers in decline, the lack of prey availability throughout the SRKW range coupled with the impact of vessel disturbance makes it very hard for these orcas to thrive. However, it is the ongoing impacts of toxic contaminants in their food and habitat that poses another of the greatest threats to their long-term survival.

Scientists are aware of various toxic chemicals that exist in the Salish Sea and its many rivers, streams, and tributaries. Persistent organic pollutants, such as polychlorinated biphenyls (PCBs), pose the greatest toxic threat to killer whales. While PCBs were banned from use decades ago, they resist breaking down in the environment and can settle in sediment on the seafloor, entering the food chain through bottom-feeding species and re-entering the water column when sediment is disturbed.

Urban view with pollution from industry, cars, and stormwater near Puget Sound showing how toxics enter the food web in plankton and increase through herring and salmon, and concentrate in an orca.

Contaminants of emerging concern also pose threats, like 6PPD-q, a chemical used to extend the life of synthetic rubber products such as vehicle tires lethal to salmon in low concentrations. Tire wear particles on and near roadways wash into rivers and streams during heavy rains, which can impact the health and survival of juvenile salmon and further limit prey availability for SRKW.

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The Washington Department of Fish and Wildlife

The Washington Department of Fish and Wildlife is dedicated to preserving, protecting and perpetuating the state’s fish and wildlife resources.