Pictures: Heavy Oil Seeping Into Louisiana Marshes

Dripping Oil

Photograph by Hans Deryk, Reuters

Oil drips from the rubber gloves of Greenpeace marine biologist Paul Horsman, who surveyed oil-coated shorelines near the mouth of the Mississippi River in Louisiana this week.

When oil gets trapped underground in coastal sediments, it can stay there for decades, according to Gregory Stone, director of Louisiana State University's Coastal Studies Unit. (See: "Gulf Oil Spill a 'Dead Zone in the Making'?")

For instance, on the Mississippi coast—where smaller oil spills have washed ashore in the past—researchers have found oil lingering as deep as 20 feet (about 6 meters), Stone said in early May.

Published May 19, 2010

Written in the Sand

Photograph by John Moore, Getty Images

Written by a Greenpeace activist, the letters BP—referring to the company that leased the damaged Deepwater Horizon oil rig—stand out against a pool of oil on a beach at the mouth of the Mississippi River on Monday.

Last week response workers placed an insertion tube inside the destroyed pipe connected to the 5,000-foot-deep (about 1,500-meter-deep) wellhead. About a thousand barrels a day of gas and oil from the leaking wellhead are now being brought to the surface via the tube and burned, according to the joint federal-industry task force charged with managing the spill.

Published May 19, 2010

Oil-Coated Cane

Photograph by Gerald Herbert, AP

Oil sticks to cane, a type of plant found in Gulf of Mexico marshes, on the Mississippi River on Tuesday.

In addition to killing seabirds, the oil spill is likely harming other animals less visible to the public, John "Wes" Tunnell, associate director of the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University in Corpus Christi, said by email in early May.

Infauna, or small organisms such as clams and tubeworms that live in ocean sediments, are vital food sources for shorebirds and other coastal animals.

After the 1979 Ixtoc oil spill in the Gulf of Mexico, the area's infauna were reduced by up to 90 percent, Tunnell said—a potential reason many bird species left the area in the wake of the nine-month-long spill.

Published May 19, 2010

Oil Inspection

Photograph by John Moore, Getty Images

Greenpeace marine biologist Paul Horsman inspects oil washed ashore on a Mississippi River beach this week.

History suggests marshes don't easily bounce back from oil. For instance, the 1991 Gulf War spill—which occurred when the Iraqi military intentionally spilled up to 336 million gallons (about 1.3 billion liters) into the Persian Gulf—was most toxic to Saudi Arabian marshes and mud flats.

Up to 89 percent of the Saudi marshes and 71 percent of the mud flats had not bounced back after 12 years, according to Miles Hayes, co-founder of the science-and-technology consulting firm Research Planning, Inc., based in South Carolina. (See pictures of freshwater plants and animals.)

"It was amazing to stand there and look across what used to be a salt marsh and it was all dead—not even a live crab," Hayes said last week.

Published May 19, 2010

Oil Glob

Photograph by Lee Celano, Reuters

A glob of oil clings to a reed on a beach in Southwest Pass, Louisiana, on Saturday. Globs and solid masses called tar balls are common byproducts of oil spills.

Tar balls have also been spotted on Gulf beaches in recent days. The sticky blobs can form when ocean waves concentrate surface oil slicks into clumps, which then wash ashore. The tar balls present a risk to wildlife, said Ronald Kendall, an environmental toxicologist at Texas Tech University. (See pictures of tar balls and a dead dolphin on Gulf of Mexico beaches.)

They're "not as toxic or as big a problem as a sheen of oil that gets on feathers or fur, but they can still be toxic if swallowed," he said.

With reporting by Ker Than

Published May 19, 2010