• Some species slow to recover as oil pockets remain
By Carey Restino
A quarter-century after 1,300 miles of Alaska’s shores were soiled by the Exxon Valdez oil spill, a flight over Prince William Sound looks down on a pristine environment of green hillsides and blue waters. From above, the Sound looks virtually as it did before the spill. But look below the surface, both on land and in the water, and those whose life work it is to study this environment all say the same thing — it’s not the same. In this last story of a three-part series on the spill, the Homer Tribune looks at some of the larger environmental impacts that still linger today as Alaska continues to try to recover.
Among the many surprises of the Exxon Valdez oil spill was the way the oil behaved following the spill. Few scientists would have expected that 25 years after the spill, oil with many of the same dangerous properties found that first summer could still be dug up beneath the sand. But most Alaskans now know differently. The oil, which can be found beneath the surface most readily on beaches that were heavily oiled, remains. A 2001 survey by Auke Bay Laboratories of intertidal areas of the Sound found oil in over half the thousands of pits it dug.
Even more alarming, said a 2008 report by Exxon Valdez Oil Spill Trustee Council was that many of those sites surveyed found the subsurface oil breaking down very slowly.
“At this rate, the remaining oil will take decades and possibly centuries to disappear entirely,” the report noted.
At greatest risk from this lingering oil are marine animals such as sea otters and harlequin ducks who feed in the intertidal zone, especially those who have a small range. Sea otters, as well as harlequin ducks, were recently moved onto the list of species officially listed as recovered from the spill.
But the report notes that while the overall otter and harlequin duck population may be doing well, some studies showed elevated levels of polycyclic aromatic hydrocarbons in birds and marine mammals indicative of continued exposure to oil.
“The potential for long-term damage remains wherever oil persists after an oil spill, whether it is buried in the ocean bottom, marshes, mangroves or other habitats that are not dynamic,” the report noted.
Among the most heart-breaking images from the spill was snapped just hours after the oil began oozing into the Sound. A pod of Orca whales was documented swimming through the ever-expanding sheen, coming up for air right in the middle of the crude slick. Homer’s Craig Matkin and Eva Saulitus, as well as three other whale biologists studied these whales for the next two decades, producing a report on the populations of two pods of whales as they floundered following the spill. What they found was grim — a large number of whales disappeared in the years following the spill, including many of the essential reproductive-age females.
A resident group of killer whales, known as AB Pod, had 36 members prior to the spill. Six days after the spill, seven of those whales photographed in the fall of 1988 were missing. Another six dropped out of sight by the next winter, a 33 percent mortality loss in a little over a year.
Today, the AB Pod is split into two pods, one of which has failed to recover and currently numbers 20 whales. The 2008 report noted that while other resident pods in northern Gulf of Alaska increased in size an average of 3.2 percent per year in the years following the spill, the AB Pod lagged behind.
“This is essentially due to a low reproductive rate, which is the result of a disproportionate loss of females from the group at the time of the spill and apparent breakdown in social structure,” Matkin said in an email.
A second pod, known as the AT1 pod, was even more dramatically impacted. In the 1980s, the pod had 22 members. Four of these whales were photographed swimming through the oil and three of those photographed were missing the following year, the report said. Another six disappeared in the years following, and no new calves have been seen in the pod. Today, there are seven whales left in the AT1 pod, as many of the remaining whales who were in their 30s and 40s died, and the pod is listed as depleted under the Marine Mammal Protection Act, the report said.
“The spill was basically the last nail in the coffin of this group and essentially eliminated any chance of their long-term survival,” Matkin said. “Females are now getting too old to reproduce.”
The report said the sharp declines in the pods of whales documented in the region following the spill indicates a link between the oil and the whale deaths, though few of the whales were found for autopsy as whales sink when they die. The whales were likely harmed by breathing in large quantities of evaporating gasses out of the oil as well as eating lethargic, oiled harbor seals, the report said.
“In view of the mortality patterns of AB Pod and the AT1 Group and other resident pods during the 21 year study period, it is highly unlikely that this mortality was simply coincidental with the (Exxon Valdez oil spill),” the report said.
Prior to the Exxon Valdez oil spill, the Prince William Sound supported a herring fishery valued at as much as $20 million annually, the lifeblood of the community of Cordova and a major fishery for the state. Alaska Fish and Game figures indicate fishermen were catching between 10,000 and 20,000 tons of herring annually. The nutrient-rich herring were also an important subsistence resource in the region, as well as significant to many other species, such as seabirds.
Scott Pegau, research program manager for Oil Spill Recovery Institute, said immediately following the spill, the herring stocks remained healthy. It wasn’t until 1992 and 1993 – after the natural resources damage assessment – that the fishery collapsed.
“No one was anticipating a lag,” Pegau said. “That was one of the lessons that many of us took away from this.”
Pegau said there were many theories about why the herring crashed when it did — the zooplankton levels, which are food for herring, were low, potentially causing stress for the small, fatty fish. Many believe disease was the culprit in the sudden reduction in numbers, but link the herring’s susceptibility to the disease to stress from the spill. Herring live in near shore waters and come up and get air at the surface for their swim bladders, so their exposure to the actual sheen was likely greater than that of other fish, such as salmon. Salmon stocks in the region recovered quickly, allowing for that fishery to continue a year after the spill.
“There’s the exposure to the oil, and the fish were starving because the oil took their food source away,” Pegau said. “That put them in a stressed condition that made them ripe for an outbreak.”
Since 1993, when the fishery closed, the population has recovered too slowly to allow a commercial fishery harvest, though numbers have risen to levels that support much of the needs of animals that depend on the fish as a food source.
Not everyone is convinced that it was the spill that caused the herring to crash. As with many fish populations, fluctuations are common from year to year. And some point to salmon hatcheries in the region, questioning the impact introducing hundreds of millions of juvenile salmon into the system might have on the herring population. But the herring’s slow recovery is unusual. Historic records kept from the early 1900s indicate the herring may have been overfished, but returned to an abundant population within four to six years, Pegau said.
But, like sea otters and some 13 other species now on the recovered or recovering list following the oil spill, there may be light at the end of the tunnel, Pegau said. Indicators are turning up that the strong recruitment class of herring may be on the horizon.
“I’m actually very optimistic,” Pegau said. “But we won’t know until April of 2015 if that optimism is warranted.” Pegau said those who studied the herring collapse are largely surprised of the rebound, if it is in fact occurring, hasn’t happened earlier.
“You look out in Prince William Sound and most everything else has recovered,” he said, adding, however, that the ecosystem was forever changed by the spill. “It will never be like it was before, because the whole nature of the ocean keeps changing. Even if the spill hadn’t happened, it wouldn’t be the same. We don’t know how it would be different, and that makes it really hard to understand the full impacts an oil spill can have on the natural variability.”
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