US: Sea otters are recovered following 1989 spill

Mar 02, 2014 by Dan Joling
This photo taken Thursday, Feb. 27, 2014, in Valdez, Alaska, shows a sea otter in the bay near the ferry dock. The U.S. Geological Survey report released Friday, Feb. 28, 2014, concludes sea otters in Alaska's Prince William Sound have recovered to levels seen before the Exxon Valdez oil spill nearly 25 years ago. (AP Photo/Mark Thiessen)

(AP)—A U.S. federal study of Prince William Sound sea otters affected by crude oil spilled from the Exxon Valdez has concluded that the marine mammals have returned to pre-spill numbers a quarter century after the disaster.

Sea otters feed on clams. Crude oil from the remained in sediment years after the spill and likely contributed to a delay in sea otter recovery, said lead author and research biologist Brenda Ballachey.

"One of the lessons we can take from this is that the chronic effects of oil in the environment can persist for decades," Ballachey said by phone Friday.

The 987-foot (300-meter) Exxon Valdez, carrying more than 53 million gallons of Alaska North Slope crude oil, strayed from shipping lanes on March 24, 1989, and struck Bligh Reef. The damaged supertanker leaked 10.8 million gallons. Crude oil flowed southwest along nearshore waters all the way to Kodiak Island.

Responders recovered nearly 1,000 sea otter carcasses from the entire spill area. The estimated number of immediate deaths attributed to the spill ranged from fewer than a thousand to 3,000, Ballachey said.

Sea otters rely on their thick fur to survive in cold water. Fur covered by oil loses its insulating value. A sea otter with oiled fur must groom itself, which leads to the ingestion of oil and causes other problems, including time taken away for feeding, Ballachey said.

This photo taken Thursday, Feb. 27, 2014, in Valdez, Alaska, shows a sea otter in the bay near the ferry dock. The U.S. Geological Survey report released Friday, Feb. 28, 2014, concludes sea otters in Alaska's Prince William Sound have recovered to levels seen before the Exxon Valdez oil spill nearly 25 years ago. (AP Photo/Mark Thiessen)

In the years following the spill, she said, chronic problems connected to lingering oil likely may have killed as many sea otters as in the first year.

"Our modeling exercises suggest that the number of otters that died from chronic exposure was close to the same number as died from acute exposure," she said.

Researchers studied sea otters with aerial surveys and annual carcass recoveries. On the demographic side of sea otter studies, scientist looked at overall numbers and the ages of animals found dead. In areas unaffected by a spill, most of the dead animals recovered are very young or very old. Carcasses recovered from heavily oiled areas of Prince William Sound showed sea otters dying in the prime of their lives.

A decade after the spill, sea otters still were not returning to areas hit hard by oil, such as the Knight Island archipelago and lingering oil was detected as a reason. Through 2007, according to an earlier study, sea otters digging in sediment were coming into contact with lingering from two to 24 times per year, Ballachey said.

Besides soiling fur, scientists detected differences in blood chemistry consistent with liver damage, Ballachey said.

This photo taken Thursday, Feb. 27, 2014, in Valdez, Alaska, shows a sea otter in the bay near the ferry dock. The U.S. Geological Survey report released Friday, Feb. 28, 2014, concludes sea otters in Alaska's Prince William Sound have recovered to levels seen before the Exxon Valdez oil spill nearly 25 years ago. (AP Photo/Mark Thiessen)

"We felt that low levels of exposure have been sufficient to affect survival of the population," she said.

Things got better after 2007. By 2009, many areas of western Prince William Sound were showing a population that matched pre-spill numbers.

Ages of dead animals in the heavily damaged areas now match areas that were not affected, Ballachey said.

Explore further: Life in the poisonous breath of sleeping volcanos

Related Stories

California's sea otter numbers continue slow climb

Sep 13, 2013

California sea otter numbers are up, according to the latest population survey led by federal, state, and UC Santa Cruz scientists. The reasons: more pups and the addition of San Nicolas Island sea otters ...

How healthy are Scotland's otters?

Feb 17, 2014

(Phys.org) —Scotland's otters are for the first time in 20 years to be included in a UK-wide study aimed at giving scientists an insight into the chemical pollutants threatening their health and the health ...

Recommended for you

Germany restricts fracking but doesn't ban it

2 hours ago

The German cabinet drew up rules Wednesday on the hitherto unregulated technology of "fracking" in Germany, narrowly restricting its use, but stopping short of an outright ban.

Life in the poisonous breath of sleeping volcanos

2 hours ago

Researchers of the University Jena analyze the microbial community in volcanically active soils. In a mofette close to the Czech river Plesná in north-western Bohemia, the team around Prof. Dr. Kirsten Küsel ...

Eggs and chicken instead of beef reap major climate gains

3 hours ago

Beef on our plates is one of the biggest climate villains, but that does not mean we have to adopt a vegan diet to reach climate goals. Research results from Chalmers University of Technology show that adopting ...

Local action needed to protect nature from global warming

5 hours ago

Stronger local management can increase the resilience of nature to the impacts of climate change, writes an international team of researchers in Science. The authors examined three UNESCO World Heritage Sites: ...

Deforestation is messing with our weather and our food

6 hours ago

Today, the National Socio-Environmental Synthesis Center (SESYNC) at the University of Maryland published new research in Nature Communications providing insight into how large-scale deforestation could ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.