Mote research highlights potential Deepwater Horizon spill impacts

February 22, 2019
By Marcy Shortuse

To the Editor:
Mote Marine Laboratory scientists found that southern flounder exposed to oiled sediment for 30 days in the lab showed evidence of stress and DNA damage, one of the latest indicators of potential impacts of the 2010 Deepwater Horizon oil spill that continues to be studied today.
The flounder study – presented at the 2019 Gulf of Mexico Oil Spill & Ecosystem Science Conference this month in New Orleans and in prep for submission to a peer-reviewed journal – is one of several oil-exposure studies in a series led by Mote Senior Scientists Dr. Dana Wetzel and Dr. Kevan Main. Wetzel, manager of Mote’s Environmental Laboratory for Forensics, is leading the toxicology task group within the C-IMAGE research consortium focused on the Deepwater Horizon impacts and based at University of South Florida.
Wetzel, Main and their teams are expanding knowledge on native Gulf of Mexico fishes using a unique exposure-research system for adult marine fish at Mote Aquaculture Research Park in Sarasota County, Florida. Their studies, using Deepwater Horizon oil or South Louisiana Crude oil, are helping to rigorously document specific ways that oil and dispersant can affect southern flounder, red drum and Florida pompano, focusing on DNA integrity, oxidative stress, immune and reproductive health, viability of offspring and other traits important for maintaining healthy fish populations.
In the newly presented study, the scientists exposed southern flounder to three grams of Deepwater Horizon oil per kilogram of sediment, a concentration that could have been observed in coastal areas of the Gulf of Mexico affected by the 2010 spill.
Even though fish have natural biochemical defenses to cope with harmful chemicals, the fish in this study could not ameliorate all of the “oxidative stress” (a potentially damaging impact) from this exposure.
Mote scientists measured the impacts of a 30-day oil exposure on key biochemical processes in the exposed flounders’ blood and specific tissues, compared with those of unexposed flounder. In exposed flounder they found disturbances in the balance between harmful chemical species called “reactive oxygen species” and defense mechanisms against them, including the natural antioxidant glutathione. Assessment of the glutathione defense mechanism indicated a decreased ability to respond adequately to the  impacts of oxidative stress – resulting in measurable impacts, in the form of DNA damage and lipid peroxidation. These responses do not mean that a fish will be sick, but they do increase the risk of health issues.
In the oil-exposed flounder, Wetzel’s team found a correlation between increasing concentrations of PAH compounds in the body and the activation of glutathione defenses. In turn, they found a correlation between  glutathione defense response and increasing signs of damage (lipid peroxidation and DNA damage).
Using these lab results to make inferences about wild fish is a complex challenge, dependent on continued and consistent research efforts, including C-IMAGE.
For more information regarding the study, go to
Hayley Rutger
Director of Mote Marine media