Southern Residents © Stewart Macintyre/CWR

In a recent BBC interview, our Science & Research Director, Dr. Giles, explained that whale feces is a treasure trove of information. From a single fecal sample—without taking blood, or using other invasive procedures such as a biopsy—you can detect a pregnancy, measure hormones and stress levels, identify diet preferences and determine exposure to contaminants, such as PCBs and oil spills.

Yet spills are not the only threats these whales face from oil, as according to the EPA, the chemicals that occur naturally in crude oil and gasoline—polycyclic aromatic hydrocarbons (PAHs)—are also produced when fuel is burned. PAH emissions from engines are monitored for pollution impacts to air quality due to their potential to cause cancer.

The endangered Southern Residents share the Salish Sea with a wide variety of vessels. Many research studies have focused on the effects of noise—yet their engine emissions are also a potential source of harm. According to the researchers, “marine mammals are inherently vulnerable to poor air quality due to their extended time at the water surface and their deep breaths.”

© Maya Sears, NOAA Permit 16163-01

Using fecal samples collected in the Salish Sea—with the aid of scent detection dogs—70 samples were analyzed for exposure to hydrocarbons (PAHs). The samples were matched by DNA profile to 34 whales from J, K and L pods, and represented animals across the spectrum—from juvenile to menopausal female.

PAHs were detected only in low levels in each sample collected from 2011 to 2013, and the analysis showed that this was consistent regardless of age, pod, or year. This led the researchers to conclude that the Southern Residents had likely only experienced “negligible exposure” to PAH in these years. This is because, unlike PCBs that accumulate over time in blubber, PAHs are more easily eliminated from the body, and therefore if PAH is detectable, the exposure must be recent.

Giles and Eba collect a fecal sample © Amanda Colbert

Their analysis also revealed something unexpected. Three samples, all collected in 2010, had significantly higher levels of PAH than the samples collected from 2011 to 2013, and were determined to have the signature of PAHs produced through combustion, suggesting that these whales had been exposed to vessel emissions.

Why would 2010 differ? Distance matters

Previous research found that measured emission levels drop to around 30% once a vessel is 100 yards from the Southern Residents, but when the distance is increased to 200 yards, emission levels drop to more negligible, or “background levels”.

Beginning in 2011, new ‘Be Whale Wise regulations increased the legally required distance between vessels, and the Southern Residents, from 100 to 200 yards.

As the researchers noted, the samples collected from 2011 to 2013 showed only background levels of PAHs, unlike the much higher levels found in some of the 2010 samples. This led them to conclude that, prior to the increase in legal distance, “the PAH exposure may have been higher… and this suggests that the whales may have experienced a decrease in exposure to combustion engine emissions following the updated vessel regulations.”

Despite this, they noted that PAH exposure from vessels “warrants continued monitoring” and so as Wild Orca takes over the important health monitoring of this population in 2022, through non-invasive fecal sample collection and analysis, we will be testing for PAHs, both to monitor exposure to vessel emissions, and oil spills.

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