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Razor clams don’t mess around after oil spills, University researchers find

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Stout razor clams may be on the cutting edge of oil spill cleanup, according to University of Louisiana at Lafayette researchers.

After simulating an oil spill, faculty and student researchers found coastal sediments that held razor clams retained 25 percent less oil than areas where the mollusks weren’t present.

That could mean clams are absorbing oily residue, or they might be burying it. Either way, they’re acting as frontline custodians combatting environmental crises, said Dr. Paul Klerks, a UL Lafayette biology professor and one of the project’s investigators.

“Our research shows that evaluations of oil spill impacts need to consider how animals living in coastal areas may influence what happens to the oil. Studies like these are important because they help determine where spilled oil will be found and how fast it will disappear,” Klerks said.

Razor clams are bioturbators, which means their burrowing reworks and moves sediment in the beaches and coastal estuaries where they live. They are ubiquitous in the western Atlantic Ocean from Cape Cod to Argentina, and throughout the Gulf of Mexico.

Feeding and digging by these “ecosystem engineers” can redistribute contaminants over a wide geographic area, potentially exposing other sea creatures to pollutants as well.

UL Lafayette researchers used a series of 30-gallon aquaria to replicate the aftermath of the Deepwater Horizon oil spill in the Gulf. The team wanted to determine how the light-shelled, semi-cylindrical clams affected what happened to the oil. 

Investigators used oil similar to that which inundated Gulf shorelines following the rig’s 2010 explosion, weathering it slightly to mimic the chemical changes that happen when petrochemicals mix with seawater. They then exposed the oil to sand that contained razor clams and other sediments that did not.

Researchers found the clams’ presence reduced contaminants on the sediments’ surface by 25 percent; however, the team noted the level of toxins below the surface had not increased, Klerks said. “We checked oil levels below the surface to assess whether the clams were burying the oil. If they were, then there should have been less oil at the surface and more oil in deeper sediment.

“We found some evidence for burrowing,” but not enough to conclude definitively that the oil’s fate rested below the sediment surface.

Where did it go? Researchers then considered microbial breakdown. That process would involve razor clams and bacteria working in tandem to eliminate the oil, Klerks explained

“Some bacteria basically eat the oil and break it down. It’s food for them.”

The clams’ burrowing could affect what kind of bacteria and how many occur in sediment and water. In turn, that could increase how quickly the oil breaks down.

Researchers tested this theory, but did not find a difference between the tanks with clams and those without.

Questions remain. While it is clear the clams’ presence affected the oil, Klerks said more study is needed to determine how and why. Another avenue University researchers are examining: how Gulf ghost shrimp interact with pollutants.

Like razor clams, ghost shrimp burrow into sediments, but tend to be more reclusive. They “are very abundant and very active. They make burrows that may be as much as 10 feet deep, so they are likely to have even more of an impact than razor clams,” Klerks said.

He explained that the tunnels’ depths mean ghost shrimp move more sediment than razor clams do. That results in more oxygen below the surface and more bacteria that potentially could consume – and therefore combat – toxins.

The new findings on how both organisms help the environment cope with contaminants “underscore the importance of healthy coastal systems,” Klerks added.

“So much depends on a vibrant coastline, from the seafood and tourism industries to the fish, shrimp and oysters we buy in the stores. Studies such as these help people decide when it is safe to go back to beaches or eat seafood following an environmental crisis.”

The Archives of Environmental Contamination and Toxicology published the team’s razor clam study in its August 2018 issue.

In addition to Klerks, its authors are Alex Kascak and Nihar Deb Adhikary, doctoral students in the Department of Biology; Dr. Alfy Morales Cazan, a postdoctoral researcher in the chemistry and biology departments; Dr. Andrei Chistoserdov, associate professor of biology; and Dr. Febee Louka, associate professor of chemistry.

Two additional authors, Amalia F. Shaik and Sommer Osman, were undergraduate researchers on the study. Both have since graduated from UL Lafayette; Shaik earned a bachelor’s degree in microbiology and Osman completed a bachelor’s degree in chemistry.

A Gulf of Mexico Research Initiative grant partially funded the study. GoMRI is a 10-year independent research program established to study the environmental effects of oil spills.
 

Photo caption: Razor clams are ubiquitous in the western Atlantic Ocean from Cape Cod to Argentina, and throughout the Gulf of Mexico. (Photo courtesy of Dr. Darryl Felder / University of Louisiana at Lafayette)

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