Infographic by Chloe Kotik

When predators consume prey, they also absorb the pollution that has accumulated in their prey’s bodies. Higher-level predators like killer whales need to eat more to meet their energetic demands, which means they end up absorbing and retaining more pollution than lower-level consumers. With each step up in the food web, pollutants become more concentrated in animal tissues, a process known as biomagnification

Many contaminants are also lipophilic, meaning that they tend to be stored in fatty tissues. As long-lived, high-level predators with lots of fatty blubber tissue, killer whales and other marine mammals are particularly vulnerable to the effects of pollution. Some pollutants also transfer from mother whales to their offspring during pregnancy and nursing, creating a multi-generational contaminant crisis. 

Using a new method developed by Dulgheriu et al. (2026), Chloe Kotik and colleagues are working to quantify concentrations of contaminants and hormones in tiny fragments of killer whale tissue known as biopsies. Biopsies are small samples of skin and blubber collected from killer whales and other marine mammal species as a method of answering questions about whale health, physiology, genetics, and condition. Each biopsy is subdivided into many tiny sections to support as many analyses as possible. This project quantifies the concentration of almost 200 different contaminant congeners, as well as five important steroid hormones: androstenedione, progesterone, testosterone, cortisol, and cortisone.

Infographic by Chloe Kotik

These five hormones can shed light on killer whale development, reproduction, health, and stress response, as well their responses to contaminant accumulation. By measuring testosterone, androstenedione, and progesterone, researchers can determine whether whales are sexually mature or even pregnant, while concentrations of cortisol and cortisone indicate stress response. This study will help scientists determine whether contaminant concentrations are impacting hormone concentrations, potentially altering important physiological processes in killer whales in the Salish Sea.  

This study makes use of previously-collected blubber biopsies on one of the most contaminated animals on the planet: mammal-eating West Coast Transient killer whales. When it comes to investigating killer whale health, West Coast Transient killer whales are the ideal study population: well-known and increasing in abundance, but still facing many of the same threats that endanger Southern Resident killer whales in their shared habitat. The results of this study will help us to better understand how all killer whales, including Southern Residents, are impacted by toxic contaminants in their environment. The results will allow us to advocate for stricter regulations on chemical manufacturing, testing, and usage in the United States and around the world.