Oil spills are known to wreak havoc on the marine environment. A research team led by Anne McElroy, a professor in the Stony Brook University School of Marine and Atmospheric Sciences, found that some of the methods used to mitigate oil spills could have negative effects on fish, especially when coupled with other environmental changes.
“We’re trying to get a better picture of what the fish in the 2010 Gulf of Mexico oil spill were experiencing,” said Irvin Huang, a graduate student in the lab. “We’re trying to slowly piece together a more realistic picture of what’s happening to them.”
Chemicals called dispersants are commonly used after an oil spill to break up oil slicks into smaller globules that can spread out in the water and be degraded by microbes.
In order to test the effects of dispersants and other factors, McElroy and her team measured the survival of fish larvae after exposure to the different conditions.
The team chose to work with larvae after initial experiments showed that they are more sensitive to change than embryos. This is likely because the larvae no longer have a protective membrane.
Dispersants, similar to the ones used in the 2010 Gulf of Mexico oil spill, and low oxygen levels in the water, also known as hypoxia, both independently resulted in a decline in fish survival.
The greatest decline in fish population was seen when the fish were exposed to oil, dispersants and hypoxic conditions together.
The team observed greater effects, which indicated an interactive effect among these stressors. McElroy’s group recently published these results in PLOS ONE.
Subham Dasgupta, a Ph.D. candidate in the lab, set out to uncover the biological reasoning behind this effect.
Dasgupta found that a key protein, CYP1A1, which breaks down hydrocarbons in oil, is greatly diminished under hypoxic conditions.
Therefore, if the water in which the oil spills is hypoxic, the fish have a limited ability to rid themselves of toxic oil components, which could contribute to the lower survival rate that was observed.
Conversely, under normal oxygen levels the fish are better able to tolerate exposure to chemically dispersed oil.
Additionally, Dasgupta has recently found that hypoxia increases damage caused by exposure to dispersed oil, and diminishes the young fish’s ability to respond to oxidative stress, which could further contribute to the decreased survival.
Overall, these findings suggest that hypoxia exacerbates the effects of oil and dispersants.
“A lot of what we study has to do with subtle things that might not kill them outright but make them more susceptible to diseases, chemicals or a combination of stressors that might make them not perform as well,” McElroy said.
These findings are important because they show that the health of the environment plays a role in how organisms can react to disasters like oil spills.
Furthermore, it provides additional support for efforts to prevent fertilizer use and runoff, which contribute to hypoxia.
In the future, the lab aims to further investigate changes in enzymes and their expression in fish that result from changes in the environment.
The lab also plans to study the impact of pharmaceutical waste that comes from sewage treatment plants on fish to better understand the impact of human activity on marine life.