Deepwater Horizon Day 18: The Definition of Oiled Wildlife

The title says it all – What is an oiled animal?

This question should raise several questions in your mind: 1) An animal is oiled if it has oil on it (followed by a “Duh!” if you were my daughter); 2) It’s a trick question, there’s a catch somewhere and I should re-read the darn thing; and 3) Oh no, Mike got some sleep and/or left the Command Post after only a 13-hr day and is becoming theoretical again.

Each of these are true. The definition of an “oiled animal” is actually fairly complex, as it can encompass a number of different presentations.  Animals can have apparent external exposure, as is typically seen with birds contaminated with a crude oil on their feathers.  Wildlife can also show inapparent external exposure, which is when birds or other animals do not have dark oil visible on their fur, feathers or scales, but you can detect oil by smell, feather matting, or other sensory clues. Thirdly, animals can have apparent internal exposure, typically seen in live animals through oil in their feces, and in dead animals by visually assessing their gastrointestinal tracts on post-mortem evaluation. Fourth, an animal can have sub-apparent internal exposure often determined by microscopically examining their organ tissues, looking for damage which could be associated with toxin exposure.  Lastly, oiling can also be determined through chemical analysis of different samples, be they feathers, swabs of skin, or tissue samples.

This is an issue that the OMTU team (actually, I have to admit a small falsehood here – we are actually the Marine Mammal and Sea Turtle GROUP, but OMMSTG just didn’t traipse off the tongue) has been battling with since the beginning of the spill, as marine mammals and sea turtles are much more likely to have less apparent external exposure and greater internal exposure than avian species.  With that in mind, our criteria for determining what an “oiled” turtle or mammal had to be developed quickly but completely, as the results could have both legal as well as financial implications.

Therefore, a written plan was developed to establish what criteria we would be using to determine the oiling status of stranded marine mammals or turtles.  From strongest to least strong lines of evidence, these include:

• Evidence of external oiling.
• Evidence of internal oiling on initial exam (oil in oral cavity or cloaca)
• Evidence of internal oiling on necropsy (oil in gastrointestinal tract)
• Evidence of pathological changes strongly associated with oil exposure on necropsy (acute respiratory damage, irritation to ocular tissues or mucous membranes)
• Strandings in the “declared spill area”.
• Strandings adjacent to the “declared spill area” within a specified distance that affected mammals or turtles may travel after being affected.

Clearly, those animals that fall in the first three of these categories can be classified as “oiled”, but where do you draw the line at for the remaining categories?  The key issue is that mammals and turtles regularly “naturally” strand in this region due to a variety of human-induced and natural causes. Diseases can cause many of the same results when examining the tissue samples. Not to mention that it is very difficult to even collect dead animals before their bodies decompose to a point where their tissues are impossible to assess.

Where, may you ask, do you then place actually chemically detecting the components of oil in the bodies of the animals that die? An excellent question – gold stars all around (especially for those who did not shudder at the mention of something you have spent years trying to forget from Organic Chemistry). Detecting the polycyclic aromatic hydrocarbon (or PAH) components of oil in the tissues of live or dead animals is often referred to as the “gold standard” to detect sub-apparent oil exposure.  However, there are a few challenges to this method. First, you again have to have fairly fresh samples (and, in the heat of LA and MS in May, that is a tough job). Second, you have to have something to compare your results to. The results of the tests will be actual numbers, giving concentrations of these analytes in the sample – they will not tell you “Yes, Mike, it is positive”. You have to have something to compare these numbers with – to act as a baseline.  As these samples are often in the high hundreds to thousands of dollars apiece to analyze, much of this background work has not been done to date on many species. However, samples often do exist from animals that were collected prior to the time of interest, so going to collaborating scientists is often how baseline levels can be ascertained.

And, being an inquisitive sort, you may then follow all of this up with: Why does it matter?  An animal is an animal, be it oiled or unoiled, apparent or not – especially the live ones. Another excellent point. Knowing the oiling status on the animal (and being extremely deliberate and careful in determining internal exposure) can do many things for us. First and foremost, it can tell us whether we are dealing with an animal that is sick due to oiling or due to another cause, which can then allow us to better treat that same animal – or to protect other animals if it may be harboring an infectious agent. It can also help us in future spills better associate apparent clinical signs or findings (such as the results of blood work) with levels of oil exposure, which may then in turn lead to better animal care. Similarly, we can better learn how oil may affect wildlife species through pathological evaluations of animals that succumb during spills.  And, lastly, determining oiling status in these animals can allow a more accurate Natural Resource Damage Assessment to be completed, therefore enabling a fairer financial settlement to be reached and restoration projects to move forward.

So, unlike “CSI”, where the answer to the stickiest of questions are answered in a 60 minute span, it can often take weeks or months to completely evaluate whether wildlife are oiled during spills. By fully understanding the myriad descriptors of “oiled” in the animals we are examining, and applying the best science possible towards teasing out the more subtle of findings, we can best define what “oiled wildlife” is in the most accurate manner.

– Mike