They're top predators among insects but food for birds and fish.
Hooper-Bui said she expected their numbers to bounce back the following year: "Instead, what we saw was worse."
The reason, she suspects, is that the oil that sank into the bottom of the marsh after the spill hasn't broken down at the same rate as the crude that floated to the surface.
Instead, it's in the sediments, still giving off fumes that are killing the insects.
Some napthalenes -- crude oil components most commonly known for their use in mothballs -- appear to have increased since the spill, she said.
"They're volatile, and they're toxic," Hooper-Bui said. "And they're not just toxic to insects. They're toxic to fish. They're toxic to birds. They cause eggshell thinning in birds. We think this is evidence of an emerging problem."
Hooper-Bui said crickets exposed to the contaminated muck in laboratories die, and when temperatures were increased to those comparable to a summer day, "the crickets die faster."
By August 2011, the number of grasshoppers had fallen by 70% to 80% in areas that got oiled.
"By 2012, we were unable to find any colonies of ants in the oiled areas," she said.
Then on August 29, 2012, Hurricane Isaac hit southeastern Louisiana. The slow-moving storm sat over Barataria Bay for more than 60 hours as it crawled onto land.
When Hooper-Bui went back to the marshes after the storm, she had a surprise waiting for her.
"We discovered in Bay Batiste large amounts of what looked like somebody had poured motor oil all over the marsh there," she said. "About three-quarters of the perimeter of northern Bay Batiste was covered in this oil."
The chemical fingerprint of the oil matched the oil from the ruptured BP well, Hooper-Bui said. Other scientists confirmed that Isaac kicked up tar balls from the spill as far east as the Alabama-Florida state line, more than 100 miles from where the storm made its initial landfall.
Far from the shoreline, patches of oil fell to the bottom of the Gulf in a mix of sediment, dead plankton and hydrocarbons dubbed "marine snow." It fouled corals near the wellhead, and it's still sitting there.
"If you took a picture of a core (sample) that was collected today and took a picture of a core that was taken in September 2010, they look the same," University of Georgia oceanographer Samantha Joye said.
"What's really strange to me is, the material is not degrading," Joye added. "There's something about this stuff, the carbon in these layers, that's not degrading."
Normally, microbes go to work on free-floating hydrocarbons almost immediately, digesting the compounds. The controversial large-scale use of chemical dispersants was supposed to accelerate that process by breaking up the oil into smaller droplets that could be more easily consumed.
But that's not happening to this layer, Joye said, and the reason is unclear.
"The first thing everyone asks is, 'Do you think it's dispersants?' And I can honestly tell you, we don't know," she said.
During the spill, scientists warned that fish eggs and larvae, shrimp, coral and oysters were potentially most at risk from the use of dispersants. The Environmental Protection Agency later reported that testing found the combination of oil and dispersants to be no more toxic than the oil alone.