Thousands of individual animals died as a result the Exxon Valdez oil spill. Some died soon after contact with the oil. Others died more slowly as a result of the toxins. It is difficult to measure how animal populations continue to be affected by contact with oil after the cleanup. The long-term harm from chronic exposure to the chemicals in oil remains a problem in some areas, especially where oil can still be found under rocks. Since 1990, scientists have been gathering data about locations where oil continues to linger, as well as the movement of toxic chemicals throughout the Prince William Sound ecosystem.
The Lingering Oil project is studying the recovery of harlequin duck and northern sea otter populations in Prince William Sound because there are long-term health concerns for both of these populations. The Gulf Watch Alaska team is collecting data by taking samples in both oiled and non-oiled sites in Prince William Sound. Click on the images below to learn more about these two species.
Scientists use a variety of skills to capture ducks and otters in order to collect tissue samples. These methods are designed to safely capture the animals and then release them unharmed. According to Dr. Esler, “It might not be the greatest day for the animals, [but] their long-term survival is not compromised.”
To capture harlequin ducks, the team uses a floating mist net. This net sits above the water like an invisible wall. As the ducks come in for a landing, they are trapped in the net. Researchers can then safely remove the ducks and take them to the veterinarian for sampling.
Capturing sea otters is a bit more challenging. These cute and fuzzy creatures are, in fact, the largest member of the weasel family (the Mustelids). This is a group of animals who are not known for their sweet and cuddly personalities. Think of a sea otter as a floating badger or wolverine!
Watch the video below to see divers use a Wilson Trap to safely capture and handle sea otters for sampling.
VIDEO: Capturing Sea Otters
United States Geological Survey (USGS) video showing how divers use Wilson traps to capture sea otters in the wild. (3:53)
The lingering oil studies occur in western Prince William Sound, which is where the oil from the Exxon Valdez oil spill landed, and actually there’s still some oil out there today – small pockets of oil that’s buried in sediments on beaches, throughout western Prince William Sound. So that’s where the lingering oil issues are still important to track.
From the USGS perspective, we’re looking at effects of that lingering oil on wildlife. So considering effects of exposure to that lingering oil, and also to understand what that might mean to individuals and populations of the wildlife that live out there. The main species that we’re thinking about in terms of lingering oil are harlequin ducks and sea otters, and that’s because there’s a long history of understanding that lingering oil’s been an important constraint on population recovery of those two species, and so we’ve spent a lot of time trying to understand the timeline and the mechanisms by which those species are recovering from the oil spill.
We’ve measured exposure in a number of different ways. For example, with harlequin ducks we’ve used an enzyme called cytochrome P450 1A. It’s a long word basically for an enzyme that gets induced when any vertebrate’s exposed to hydrocarbons. So if you and I were exposed to oil, we would have an induction of that enzyme that would be measurable and then could tell us whether one has been exposed to that.
The enzyme itself is part of a cascade of physiological processes that any vertebrate goes through once they’ve been exposed to oil. And it could be indicative of physiological harm, or it could be indicative of just exposure without physiological harm. So we’re not inferring harm from induction of the enzyme, what we’re inferring is that they’re still exposed to oil with the potential for harm.
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Concentration (n): the amount of something in a specific place or given volume
Recovery (n): a return to a normal state of health
Tissue sampling (n): various procedures to obtain bodily fluids, muscle, skin, fur or feathers for testing