Mystery in the Marsh: Where are the bugs?

Bay Jimmy, La. — LSU research assistant Brooke Hesson, brushing a net across some marsh grass, makes a somewhat surprising discovery.

"There's a beetle in this one, a pretty beetle," Hesson said, noting that beetles are rare in this section of oiled marsh along the shores of Barataria Bay.

"We started looking at insects because they're great indicators of what's happening with stressors in the environment," said Dr. Linda Hooper-Bui of the LSU Disaster Ecology Lab.

Hooper-Bui studies critters at the base of the food web in areas that were heavily oiled during the BP Macondo well blowout of 2010.

Researchers expected the population to be impacted by oil in the first year and then bounce back. In some areas, that has yet to happen.

"I would say a couple weeks ago it was the worst I've seen out here," Hooper-Bui said.

In some of those places, researchers have found only adults, indicating the insects flew into the site virtually devoid of babies.  Hooper-Biu noted, "We don't see any other life stages."

However, their concern is often not so much what they see as what they do not hear. Areas of the marsh, normally teeming with life, have fallen silent.

"The flitting of the wings, of the dragonflies, you just don't have that here," said Hoope-Bui.

The evidence for what is wrong points to a pair of suspects: naphthalene and methylnaphthalene, two of the tens of thousands of compounds found in crude oil.

"It's a good explanation because naphthalene is an insecticide and it's volatile and it's very toxic," said Hooper-Bui, noting that the evidence is not conclusive.

What puzzles them more are the concentrations of the compounds, which are rising three years after the spill.  Researchers theorize that, as oil breaks down in the marsh, the compounds get released.

With temperatures heating up, Hooper-Bui expects oil baking in the sun to crack, releasing more toxins and, perhaps, claiming more of the spill's smaller victims.