A new report by two LSU researchers outlines how even very low exposure to oil from the BP Deepwater Horizon oil leak could affect fish populations in the future.

A research team led by Fernando Galvez and Andrew Whitehead, assistant professors of biological sciences at LSU, wrote the report published in the Proceedings of the National Academy of Sciences.

Their study shows that, despite very low to non-detectable concentrations of oil constituents in the water and in fish tissues, biological effects in fish indicate dramatic responses that are indicative of exposures to the toxic components of oil. 

The researchers looked at genetic changes in fish before, during and after areas were oiled and compared those results with changes in fish in areas that didn’t receive obvious oiling, Whitehead said.

The cellular response was normal in areas were there was no oil, but in areas where there was oil, researchers saw a change that indicated a response to toxic exposure, Whitehead said.

One of the changes caused by the cellular effect was that the estrogen signal — needed for healthy reproduction — was turned down in fish, he said.

Another impact was in the development of fish gills, important for fish survival in the highly changeable conditions of Gulf Coast marshes.

“Those gills are very deformed,” Galvez said.

The researchers also took water from oiled and non-oiled areas and exposed laboratory fertilized eggs to each to measure the impact on development.

The same changes in genes were found — there was no change in the eggs in oil-free water while there was change in eggs from oil-contaminated areas.

Currently, researchers are doing the same laboratory testing using oiled and non-oiled sediment, and although it’s not been published yet, initial results are showing large developmental effects, Galvez said.

“Fewer are going on to hatch, and hatching is delayed,” Galvez said. “These effects are going to persist.”

The effects persist because oil trapped in sediments on the Gulf floor get stirred up into the water column by storms or weather events, he said.

Whitehead said these are some of the early warning indications that there could be population declines in the future.

Last year, there was a “massive effort” to test fish tissues to confirm that they were safe for human consumption, Whitehead said, and Gulf seafood was declared safe.

“That was justified. I agree with that,” Whitehead said.

However, just because the fish is safe to eat, doesn’t mean that the fish population is healthy or will be able to reproduce normally, he said.

The long-term effects on fish should be monitored, he said.