| Summary: | The Southern Resident killer whale population (SRKW; Orcinus orca) feed primarily on Chinook salmon, which is currently their primary source of exposure to toxics. We measured lipophilic persistent organic pollutants (POPs: PBDEs, PCBs, and DDTs) in SRKW scat (fecal) samples to quantify variations in toxicant levels by pod, sex, and reproductive class, as well as prey availability. We also measured polycyclic aromatic hydrocarbons (PAHs), which do not generally bioaccumulate and would reflect recent exposure to oil, engine (combustion) exhaust, among other potential exposure sources. Samples were collected using detection dogs that use scent to locate fresh SRKW scat on the water’s surface. We collected 267 samples during four 5-month study periods between 2010 and 2013. POP levels in scat had expected trends, such as increasing with age and decreasing by number of calves (for adult females). POPs were also highest when the whales primary prey source was at low seasonal abundance, presumably due to metabolizing endogenous lipid stores. By contrast, overall measures of PAHs were low (ppb, wet weight), as expected. However, PAHs indicative of motor exhaust versus oil exposure were relatively high prior to implementation of guidelines aimed at increasing vessel distances to the whales. Results point to the value of monitoring POPs by age, sex and reproductive class and in relation to changes in prey abundance to help identify what reproductive classes are most at risk to high toxic loads, what season the liability is greatest, and whether prey recovery and clean up efforts are working. The PAH exposure data will be available as baseline in SRKW feces in relation to environmental events over time, such as the circumstance of an oil spill in the Salish Sea. Addressing toxics and other vulnerabilities is important for SRKW recovery.
|
|---|