In gulf oil spill's long reach, ecological damage could last decades (WP)

[charlesg]

http://www.washingtonpost.com/wp-dyn/content/article/2010/06/05/AR2010060503987.html

In gulf oil spill's long reach, ecological damage could last decades
By Joel Achenbach and David Brown
Washington Post Staff Writer
Sunday, June 6, 2010; A01

Snorkeling along a coral reef near Veracruz, Mexico, in 2002, Texas biologist Wes Tunnell spotted what looked like a ledge of rock covered in sand, shells, algae and hermit crabs. He knew, from years of research at the reef, that it probably wasn't a rock at all. He stabbed it with his diving knife. His blade pulled up gunk. "Sure enough, it was tar from the Ixtoc spill," Tunnell said. Twenty-three years earlier, in 1979, an oil well named Ixtoc I had a blowout in 150 feet of water in the southern Gulf of Mexico. The Mexican national oil company Pemex tried to kill the well with drilling mud, and then with steel and lead balls dropped into the wellbore. It tried to contain the oil with a cap nicknamed The Sombrero. Finally, after 290 days, a relief well plugged the hole with cement and the spill came to an end - but only after polluting the gulf with 138 million gallons of crude. That remains the worst accidental oil spill in history - but the Deepwater Horizon blowout off the Louisiana coast is rapidly gaining on it...

Ecosystems can survive and eventually recover from very large oil spills, even ones that are Ixtoc-sized. In most spills, the volatile compounds evaporate. The sun breaks down others. Some compounds are dissolved in water. Microbes consume the simpler, "straight chain" hydrocarbons -- and the warmer it is, the more they eat. The gulf spill has climate in its favor. Scientists agree: Horrible as the spill may be, it's not going to turn the Gulf of Mexico into another Dead Sea. But neither is this ecological crisis going to be over anytime soon. The spill will have ripple effects far into the future, scientists warn. "This spill will be lasting for years if not decades," said Doug Inkley, senior scientist at the National Wildlife Federation. Some of the immediate effects of a spill are obvious. But some types of ecological damage are hard to measure and can take years to document. Many of the creatures that die will sink to the bottom, making mortality estimates difficult. Damage to the reproduction rate of sea turtles may take years to play out.

The Exxon Valdez spill of 11 million gallons killed as many as 700,000 sea birds and 5,000 sea otters initially, but even 21 years later, populations of sea otters in areas of Prince William Sound haven't recovered. The Pacific herring population collapsed after the spill for reasons that remain in dispute among scientists. Two intensely studied pods of killer whales in the sound suffered heavy losses in the spill and have struggled since. One of the two pods has no more reproductive females. It is doomed to extinction. And the oil? "It's still sitting there," said Stan Rice, program manager for habitat studies at the National Oceanographic and Atmospheric Administration's Auke Bay Fisheries Lab. "It's still liquid, you can still smell it and touch it."...

There are on record since 1970 about 1,700 spills from tankers in which at least 2,100 gallons of oil were discharged into water. Scientists have been monitoring the effects of some of them for decades, including a 189,000-gallon spill that occurred off Cape Cod in September 1969. Five years after that spill, fiddler crabs in the oiled marsh were sluggish and reproduced poorly. In many cases they dug burrows too shallow to protect themselves over the winter. Astonishingly, many of those problems remained 35 years later, when a graduate student, Jennifer Culbertson, surveyed the marsh. She found that the fiddler crabs reacted slowly to startling motions, apparently the result of a narcotic effect of oil that still formed a visible layer four inches below the marsh surface. (A similar clumsiness has been seen in juvenile spot fish when they chew on sediments contaminated with compounds from oil.) When the crabs burrowed down and hit the layer of 40-year-old oil, they veered horizontally...

Beaches get scrubbed by waves and storms, but marshes can develop tar mats lasting decades, Tunnell said. He said the beaches are a 3 on a scale of 1 to 10 in terms of sensitivity to oil spills, but the marshes are a 10. Attempts to clean a marsh will backfire. After the huge Amoco Cadiz spill of 68 million gallons off Brittany in 1978, French authorities scraped the top off the oiled marshes. It was a mistake: Most never came back...