‘The oil is not gone yet. This disaster is not over. There are embryos right now that are still getting exposed to that oil.’
By Bob Berwyn
SUMMIT COUNTY — Oil from the Deepwater Horizon disaster causes very specific and potentially lethal defects in fish, including heart problems and loss of facial cartilage.
The oil also prevents fish from swimming away from danger, probably because of damage to sensory neurons, according to a study published this week in BioMed Central’s open access journal BMC Biology.
In a controlled lab setting, Dr. Michael Barresi and his students at Smith University in Massachusetts exposed zebrafish (a common freshwater fish often found in aquariums) to concentrations of oil that probably still exist at similar levels in the gulf today, two years after the Macondo Well spewed millions of gallons of crude oil into the Gulf.
Zebrafish were used because they provide an established model for looking at impacts to embryonic development at the cellular and molecular level. Embryonic development is very similar for all vertebrate species, Barresi said.
“The processes that control how a head forms, how an eye forms are same if you’re a fish or a human,” he said, explaining that exposure to similar levels of oil very likely caused similar defects in native Gulf species.
He hopes the results of the study will be used by biologists looking at impacts to native Gulf vertebrate species. For example, researchers studying an unusual spike in dolphin deaths, including stillborn dolphins, could examine those dead animals for similar impacts.
“Those still born dolphins … are closest thing that we have (to embryos). I’d be very interested in knowing of any of those dolphins have any of those defects that I’ve described,” he said, suggesting that researchers could look at the jaws and cardiovascular systems of the dead dolphins for signs that the oil had similar impacts as shown in the lab experiment with the zebrafish.
“This oil is not gone yet. This disaster is not over. There are embryos right now that are still getting exposed to that oil,” Barresi said, adding that the results of his study show that robust, long-term monitoring is needed in the Gulf to track these types of impacts.
“The experiment was designed to be able to say exactly what the oil is doing … to get at the why and how of what the oil is doing,” Barresi said, explaining that the observed defects are likely due to problems with early stem cell development.
“The oil is actually impairing the development of certain type of cell (neural crest cells),” he said.
“The other, completely novel problem is with the larval ability to swim away from a stimulus … That’s an innate, genetically regulated response, important for survival. The oil impairs that ability,” he said, adding that up to 30 percent of the zebrafish larvae were completely paralyzed and don’t swim away from stimulus at all.
“Those that do are impaired. They don’t swim as long … That’s a really big problem for survival,” he said, again explaining that the impacts are targeted to very specific cells and areas of development.
“Much of their nervous system is really fine. The problem is in the peripheral nervous system. Those processes are significantly reduced, including reduced sensitivity to touch,” he said.
It’s not clear if the impacts are caused by unique chemical constituents of the Macondo oil, but some followup research by Barresi’s lab may help figure out which components in the oil are causing these defects.
What is clear is that the oil only impacts certain cells in specific tissue at specific times during embryogenesis, and not at the early stages of gastrulation, but during later stages of development.
“We need to, in a very robust way, continue surveying species the gulf for the long-term, 20 years,” he said. “The only way we’re going to know if any of this occurred is through consistent sampling … that way we can see a dip in species or see whether full generations are going to be impacted.
“If we know that, then in future oil spills we can take a quick and immediate assessment with some predicative measures of what that oil is going to do and what our response will be — should we be really scared, or not?”