Exxon Valdez: 25 Years After

From Science: 25 Years After the Exxon Valdez, Where Are the Herring?

Twenty-five years ago this week, the oil tanker Exxon Valdez slammed into Bligh Reef in Alaska's Prince William Sound, causing what was, at the time, the largest oil spill in U.S. waters. At least 250,000 barrels of crude created a slick that stretched 750 kilometers and killed an estimated 250,000 seabirds, 2800 sea otters, 22 killer whales (orcas), and billions of salmon and herring eggs. Exxon made numerous payments to settle legal claims that resulted from the 24 March 1989 wreck, including a $900 million civil penalty dedicated to ecological restoration and research. A quarter-century later, that settlement continues to pump some $3 million a year into spill-related science, with plans to continue extensive monitoring through 2032. Oceanographer W. Scott Pegau helps oversee those programs as the research program manager of the Prince William Sound Oil Spill Recovery Institute in Cordova, Alaska. He spoke with Science about what we do and don't know about the ecosystem's recovery. (This interview has been edited for brevity and clarity.)

Three million a year?  Not a bad sum.  That will keep a small passel of scientists (scientists come in passels, like crows come in murders, if you didn't know) busy for a year.  I wonder how much of that original $0.9 billion (with a "b") is left.  3 million a year implies an endowment of something on the order of $60 million, using a nice round number of a 5% yield.

Q:How is the wildlife of Prince William Sound doing?

W. S. P.:A number of species are considered recovered. Fairly recently, [biologists declared] sea otters and harlequin ducks recovered. Those are the last two big ones. Then there is one pod of orcas that is on its way to extinction. [The pod, one of eight resident in the sound, had 36 members at the time of the spill.] Essentially, the pod no longer has viable females and is never going to recover.

That's sad; and I think getting a "new" pod of killer whales established could be pretty difficult.

There are some species that are "unknown," and they are going to continue to be unknown because there just wasn't enough baseline information to ever be able to truly evaluate if they have recovered. Some birds, including Kittlitz's murrelets and marbled murrelets, are in that category. And some fish.

Yep, if you don't know the state of a population before such an event, it's hard to blame what you find later on it.

Q:Herring is still a big unknown, right?

W. S. P.:Yes, herring is a really interesting case. The population collapse occurred 3 years after the spill. In the winter of 1992–93, [fishers] were expecting a large fishery, but when they went out less than 25% of the fish were there, and they appeared lethargic and diseased. There are definitely some different opinions as to why it collapsed. It could have been a combination of nutritional stress and oil exposure. We know levels of zooplankton [which herring eat] were low after the spill, and that the herring had direct pathways for oil exposure, which could have weakened their immune system.

One thing that makes it complicated is natural variability. Herring have a boom-bust cycle, and we know that in the past the [Prince William Sound] stock has collapsed and recovered. Before the spill we were running 80,000 to 100,000 tons of spawning stock. Now, we've been bouncing around just below 22,000 tons. That level is what the local community cares about; once we exceed it, the fishery can reopen.

Chesapeake Bay has it's own herring issues, and we don't have a major oil spill to blame.  A more or less ongoing minor one, though.

Q:What are some other active research questions?

W. S. P.:A major one is lingering oil. If you go out and know what you are looking for, you can still find oil trapped within the beach. Dig a hole and it comes out of the sediment in droplets; it appears to be fresh. It looks like the [degradation] rate is between zero and 4% annually, and 4% is at the extreme high end. Studies suggest it isn't surfacing at quantities that have a large-scale ecological impact, but it is definitely out there.

We really need to figure out the mechanics of oil entrapment, and how it moves through sediments. It's a really important question because if you don't understand that, we don't know whether we can get the oil out of the sediment, or get it out without causing more harm than good.

One of the things they tried at the time of the original spill was to clean the beaches and cobbles with steam and chemicals. It turned out to have done more harm than good by killing whatever community was there.  Oil degrade very slowly in cold water, and the resulting organic poor community.

Q:What's next?

W. S. P.:We're putting a lot of work into understanding natural variability so we can better understand the impacts of something like a spill. Officially, [the settlement fund] kicked off a 20-year-long monitoring program 2 years ago, and we already have some records that date back 25 years. So, hopefully, one legacy of this is that researchers will have some very long-term records of the ecosystem that will help us understand how it is changing.